2020-07-15 07:16:16

by Anup Patel

Subject: [PATCH v3 0/4] Dedicated CLINT timer driver

The current RISC-V timer driver is convoluted and implements two
distinct timers:
1. S-mode timer: This is for Linux RISC-V S-mode with MMU. The
clocksource is implemented using TIME CSR and clockevent device
is implemented using SBI Timer calls.
2. M-mode timer: This is for Linux RISC-V M-mode without MMU. The
clocksource is implemented using CLINT MMIO time register and
clockevent device is implemented using CLINT MMIO timecmp registers.

This patchset removes clint related code from RISC-V timer driver and
arch/riscv directory. Instead, the series adds a dedicated MMIO based
CLINT driver under drivers/clocksource directory which can be used by
Linux RISC-V M-mode (i.e NoMMU Linux RISC-V).

The patchset is based up Linux-5.8-rc5 and can be found at riscv_clint_v3
branch of: https://github.com/avpatel/linux.git

This series is tested on:
1. QEMU RV64 virt machine using Linux RISC-V S-mode
2. QEMU RV32 virt machine using Linux RISC-V S-mode
3. QEMU RV64 virt machine using Linux RISC-V M-mode (i.e. NoMMU)

Changes since v2:
- Rebased series on Linux-5.8-rc5
- Squashed PATCH3 onto PATCH2 to preserve GIT bisectability
- Moved PATCH4 before PATCH2 to preserve GIT bisectability
- Replaced CLINT dt-bindings text document with YAML schema
- Use SiFive CLINT compatible string as per SiFive IP block versioning

Changes since v1:
- Rebased series on Linux-5.8-rc2
- Added pr_warn() for case where ipi_ops not available in PATCH1
- Updated ipi_inject() prototype to use "struct cpumask *" in PATCH1
- Updated CLINT_TIMER kconfig option to depend on RISCV_M_MODE in PATCH4
- Added riscv,clint0 compatible string in DT bindings document

Anup Patel (4):
RISC-V: Add mechanism to provide custom IPI operations
clocksource/drivers: Add CLINT timer driver
RISC-V: Remove CLINT related code from timer and arch
dt-bindings: timer: Add CLINT bindings

.../bindings/timer/sifive,clint.yaml | 58 +++++
arch/riscv/Kconfig | 2 +-
arch/riscv/include/asm/clint.h | 39 ---
arch/riscv/include/asm/smp.h | 19 ++
arch/riscv/include/asm/timex.h | 28 +--
arch/riscv/kernel/Makefile | 2 +-
arch/riscv/kernel/clint.c | 44 ----
arch/riscv/kernel/sbi.c | 14 ++
arch/riscv/kernel/setup.c | 2 -
arch/riscv/kernel/smp.c | 44 ++--
arch/riscv/kernel/smpboot.c | 4 +-
drivers/clocksource/Kconfig | 12 +-
drivers/clocksource/Makefile | 1 +
drivers/clocksource/timer-clint.c | 229 ++++++++++++++++++
drivers/clocksource/timer-riscv.c | 17 +-
include/linux/cpuhotplug.h | 1 +
16 files changed, 369 insertions(+), 147 deletions(-)
create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.yaml
delete mode 100644 arch/riscv/include/asm/clint.h
delete mode 100644 arch/riscv/kernel/clint.c
create mode 100644 drivers/clocksource/timer-clint.c

--
2.25.1

2020-07-15 07:16:22

by Anup Patel

Subject: [PATCH v3 1/4] RISC-V: Add mechanism to provide custom IPI operations

We add mechanism to set custom IPI operations so that CLINT driver
from drivers directory can provide custom IPI operations.

Signed-off-by: Anup Patel <[email protected]>
---
arch/riscv/include/asm/smp.h | 19 ++++++++++++++++
arch/riscv/kernel/sbi.c | 14 ++++++++++++
arch/riscv/kernel/smp.c | 43 ++++++++++++++++++++----------------
arch/riscv/kernel/smpboot.c | 3 +--
4 files changed, 58 insertions(+), 21 deletions(-)

diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index 40bb1c15a731..68de78a8eba6 100644
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -15,6 +15,11 @@
struct seq_file;
extern unsigned long boot_cpu_hartid;

+struct riscv_ipi_ops {
+ void (*ipi_inject)(const struct cpumask *target);
+ void (*ipi_clear)(void);
+};
+
#ifdef CONFIG_SMP
/*
* Mapping between linux logical cpu index and hartid.
@@ -40,6 +45,12 @@ void arch_send_call_function_single_ipi(int cpu);
int riscv_hartid_to_cpuid(int hartid);
void riscv_cpuid_to_hartid_mask(const struct cpumask *in, struct cpumask *out);

+/* Set custom IPI operations */
+void riscv_set_ipi_ops(struct riscv_ipi_ops *ops);
+
+/* Clear IPI for current CPU */
+void riscv_clear_ipi(void);
+
/*
* Obtains the hart ID of the currently executing task. This relies on
* THREAD_INFO_IN_TASK, but we define that unconditionally.
@@ -78,6 +89,14 @@ static inline void riscv_cpuid_to_hartid_mask(const struct cpumask *in,
cpumask_set_cpu(boot_cpu_hartid, out);
}

+static inline void riscv_set_ipi_ops(struct riscv_ipi_ops *ops)
+{
+}
+
+static inline void riscv_clear_ipi(void)
+{
+}
+
#endif /* CONFIG_SMP */

#if defined(CONFIG_HOTPLUG_CPU) && (CONFIG_SMP)
diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
index f383ef5672b2..226ccce0f9e0 100644
--- a/arch/riscv/kernel/sbi.c
+++ b/arch/riscv/kernel/sbi.c
@@ -547,6 +547,18 @@ static inline long sbi_get_firmware_version(void)
return __sbi_base_ecall(SBI_EXT_BASE_GET_IMP_VERSION);
}

+static void sbi_send_cpumask_ipi(const struct cpumask *target)
+{
+ struct cpumask hartid_mask;
+
+ riscv_cpuid_to_hartid_mask(target, &hartid_mask);
+
+ sbi_send_ipi(cpumask_bits(&hartid_mask));
+}
+
+static struct riscv_ipi_ops sbi_ipi_ops = {
+ .ipi_inject = sbi_send_cpumask_ipi
+};

int __init sbi_init(void)
{
@@ -587,5 +599,7 @@ int __init sbi_init(void)
__sbi_rfence = __sbi_rfence_v01;
}

+ riscv_set_ipi_ops(&sbi_ipi_ops);
+
return 0;
}
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index b1d4f452f843..8b85683ce203 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -84,9 +84,25 @@ static void ipi_stop(void)
wait_for_interrupt();
}

+static struct riscv_ipi_ops *ipi_ops;
+
+void riscv_set_ipi_ops(struct riscv_ipi_ops *ops)
+{
+ ipi_ops = ops;
+}
+EXPORT_SYMBOL_GPL(riscv_set_ipi_ops);
+
+void riscv_clear_ipi(void)
+{
+ if (ipi_ops && ipi_ops->ipi_clear)
+ ipi_ops->ipi_clear();
+
+ csr_clear(CSR_IP, IE_SIE);
+}
+EXPORT_SYMBOL_GPL(riscv_clear_ipi);
+
static void send_ipi_mask(const struct cpumask *mask, enum ipi_message_type op)
{
- struct cpumask hartid_mask;
int cpu;

smp_mb__before_atomic();
@@ -94,33 +110,22 @@ static void send_ipi_mask(const struct cpumask *mask, enum ipi_message_type op)
set_bit(op, &ipi_data[cpu].bits);
smp_mb__after_atomic();

- riscv_cpuid_to_hartid_mask(mask, &hartid_mask);
- if (IS_ENABLED(CONFIG_RISCV_SBI))
- sbi_send_ipi(cpumask_bits(&hartid_mask));
+ if (ipi_ops && ipi_ops->ipi_inject)
+ ipi_ops->ipi_inject(mask);
else
- clint_send_ipi_mask(mask);
+ pr_warn("SMP: IPI inject method not available\n");
}

static void send_ipi_single(int cpu, enum ipi_message_type op)
{
- int hartid = cpuid_to_hartid_map(cpu);
-
smp_mb__before_atomic();
set_bit(op, &ipi_data[cpu].bits);
smp_mb__after_atomic();

- if (IS_ENABLED(CONFIG_RISCV_SBI))
- sbi_send_ipi(cpumask_bits(cpumask_of(hartid)));
- else
- clint_send_ipi_single(hartid);
-}
-
-static inline void clear_ipi(void)
-{
- if (IS_ENABLED(CONFIG_RISCV_SBI))
- csr_clear(CSR_IP, IE_SIE);
+ if (ipi_ops && ipi_ops->ipi_inject)
+ ipi_ops->ipi_inject(cpumask_of(cpu));
else
- clint_clear_ipi(cpuid_to_hartid_map(smp_processor_id()));
+ pr_warn("SMP: IPI inject method not available\n");
}

void handle_IPI(struct pt_regs *regs)
@@ -131,7 +136,7 @@ void handle_IPI(struct pt_regs *regs)

irq_enter();

- clear_ipi();
+ riscv_clear_ipi();

while (true) {
unsigned long ops;
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 4e9922790f6e..5fe849791bf0 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -147,8 +147,7 @@ asmlinkage __visible void smp_callin(void)
{
struct mm_struct *mm = &init_mm;

- if (!IS_ENABLED(CONFIG_RISCV_SBI))
- clint_clear_ipi(cpuid_to_hartid_map(smp_processor_id()));
+ riscv_clear_ipi();

/* All kernel threads share the same mm context. */
mmgrab(mm);
--
2.25.1

2020-07-15 07:16:46

by Anup Patel

Subject: [PATCH v3 2/4] clocksource/drivers: Add CLINT timer driver

The TIME CSR and SBI calls are not available in RISC-V M-mode so we
separate add CLINT driver for Linux RISC-V M-mode (i.e. RISC-V NoMMU
kernel).

Signed-off-by: Anup Patel <[email protected]>
---
drivers/clocksource/Kconfig | 10 ++
drivers/clocksource/Makefile | 1 +
drivers/clocksource/timer-clint.c | 229 ++++++++++++++++++++++++++++++
include/linux/cpuhotplug.h | 1 +
4 files changed, 241 insertions(+)
create mode 100644 drivers/clocksource/timer-clint.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 91418381fcd4..eabcf1cfb0c0 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -658,6 +658,16 @@ config RISCV_TIMER
is accessed via both the SBI and the rdcycle instruction. This is
required for all RISC-V systems.

+config CLINT_TIMER
+ bool "Timer for the RISC-V platform"
+ depends on GENERIC_SCHED_CLOCK && RISCV_M_MODE
+ default y
+ select TIMER_PROBE
+ select TIMER_OF
+ help
+ This option enables the CLINT timer for RISC-V systems. The CLINT
+ driver is usually used for NoMMU RISC-V systems.
+
config CSKY_MP_TIMER
bool "SMP Timer for the C-SKY platform" if COMPILE_TEST
depends on CSKY
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index bdda1a2e4097..18e700e703a0 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -87,6 +87,7 @@ obj-$(CONFIG_CLKSRC_ST_LPC) += clksrc_st_lpc.o
obj-$(CONFIG_X86_NUMACHIP) += numachip.o
obj-$(CONFIG_ATCPIT100_TIMER) += timer-atcpit100.o
obj-$(CONFIG_RISCV_TIMER) += timer-riscv.o
+obj-$(CONFIG_CLINT_TIMER) += timer-clint.o
obj-$(CONFIG_CSKY_MP_TIMER) += timer-mp-csky.o
obj-$(CONFIG_GX6605S_TIMER) += timer-gx6605s.o
obj-$(CONFIG_HYPERV_TIMER) += hyperv_timer.o
diff --git a/drivers/clocksource/timer-clint.c b/drivers/clocksource/timer-clint.c
new file mode 100644
index 000000000000..bfc38bb5a589
--- /dev/null
+++ b/drivers/clocksource/timer-clint.c
@@ -0,0 +1,229 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ *
+ * Most of the M-mode (i.e. NoMMU) RISC-V systems usually have a
+ * CLINT MMIO timer device.
+ */
+
+#define pr_fmt(fmt) "clint: " fmt
+#include <linux/bitops.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/cpu.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/sched_clock.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/interrupt.h>
+#include <linux/of_irq.h>
+#include <linux/smp.h>
+
+#define CLINT_IPI_OFF 0
+#define CLINT_TIMER_CMP_OFF 0x4000
+#define CLINT_TIMER_VAL_OFF 0xbff8
+
+/* CLINT manages IPI and Timer for RISC-V M-mode */
+static u32 __iomem *clint_ipi_base;
+static u64 __iomem *clint_timer_cmp;
+static u64 __iomem *clint_timer_val;
+static unsigned long clint_timer_freq;
+static unsigned int clint_timer_irq;
+
+static void clint_send_ipi(const struct cpumask *target)
+{
+ unsigned int cpu;
+
+ for_each_cpu(cpu, target)
+ writel(1, clint_ipi_base + cpuid_to_hartid_map(cpu));
+}
+
+static void clint_clear_ipi(void)
+{
+ writel(0, clint_ipi_base + cpuid_to_hartid_map(smp_processor_id()));
+}
+
+static struct riscv_ipi_ops clint_ipi_ops = {
+ .ipi_inject = clint_send_ipi,
+ .ipi_clear = clint_clear_ipi,
+};
+
+#ifdef CONFIG_64BIT
+#define clint_get_cycles() readq_relaxed(clint_timer_val)
+#else
+#define clint_get_cycles() readl_relaxed(clint_timer_val)
+#define clint_get_cycles_hi() readl_relaxed(((u32 *)clint_timer_val) + 1)
+#endif
+
+#ifdef CONFIG_64BIT
+static u64 clint_get_cycles64(void)
+{
+ return clint_get_cycles();
+}
+#else /* CONFIG_64BIT */
+static u64 clint_get_cycles64(void)
+{
+ u32 hi, lo;
+
+ do {
+ hi = clint_get_cycles_hi();
+ lo = clint_get_cycles();
+ } while (hi != clint_get_cycles_hi());
+
+ return ((u64)hi << 32) | lo;
+}
+#endif /* CONFIG_64BIT */
+
+static int clint_clock_next_event(unsigned long delta,
+ struct clock_event_device *ce)
+{
+ void __iomem *r = clint_timer_cmp +
+ cpuid_to_hartid_map(smp_processor_id());
+
+ csr_set(CSR_IE, IE_TIE);
+ writeq_relaxed(clint_get_cycles64() + delta, r);
+ return 0;
+}
+
+static DEFINE_PER_CPU(struct clock_event_device, clint_clock_event) = {
+ .name = "clint_clockevent",
+ .features = CLOCK_EVT_FEAT_ONESHOT,
+ .rating = 100,
+ .set_next_event = clint_clock_next_event,
+};
+
+static u64 clint_rdtime(struct clocksource *cs)
+{
+ return readq_relaxed(clint_timer_val);
+}
+
+static u64 notrace clint_sched_clock(void)
+{
+ return readq_relaxed(clint_timer_val);
+}
+
+static struct clocksource clint_clocksource = {
+ .name = "clint_clocksource",
+ .rating = 300,
+ .mask = CLOCKSOURCE_MASK(64),
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+ .read = clint_rdtime,
+};
+
+static int clint_timer_starting_cpu(unsigned int cpu)
+{
+ struct clock_event_device *ce = per_cpu_ptr(&clint_clock_event, cpu);
+
+ ce->cpumask = cpumask_of(cpu);
+ clockevents_config_and_register(ce, clint_timer_freq, 200, ULONG_MAX);
+
+ enable_percpu_irq(clint_timer_irq,
+ irq_get_trigger_type(clint_timer_irq));
+ return 0;
+}
+
+static int clint_timer_dying_cpu(unsigned int cpu)
+{
+ disable_percpu_irq(clint_timer_irq);
+ return 0;
+}
+
+static irqreturn_t clint_timer_interrupt(int irq, void *dev_id)
+{
+ struct clock_event_device *evdev = this_cpu_ptr(&clint_clock_event);
+
+ csr_clear(CSR_IE, IE_TIE);
+ evdev->event_handler(evdev);
+
+ return IRQ_HANDLED;
+}
+
+static int __init clint_timer_init_dt(struct device_node *np)
+{
+ int rc;
+ u32 i, nr_irqs;
+ void __iomem *base;
+ struct of_phandle_args oirq;
+
+ /*
+ * Ensure that CLINT device interrupts are either RV_IRQ_TIMER or
+ * RV_IRQ_SOFT. If it's anything else then we ignore the device.
+ */
+ nr_irqs = of_irq_count(np);
+ for (i = 0; i < nr_irqs; i++) {
+ if (of_irq_parse_one(np, i, &oirq)) {
+ pr_err("%pOFP: failed to parse irq %d.\n", np, i);
+ continue;
+ }
+
+ if ((oirq.args_count != 1) ||
+ (oirq.args[0] != RV_IRQ_TIMER &&
+ oirq.args[0] != RV_IRQ_SOFT)) {
+ pr_err("%pOFP: invalid irq %d (hwirq %d)\n",
+ np, i, oirq.args[0]);
+ return -ENODEV;
+ }
+
+ /* Find parent irq domain and map timer irq */
+ if (!clint_timer_irq &&
+ oirq.args[0] == RV_IRQ_TIMER &&
+ irq_find_host(oirq.np))
+ clint_timer_irq = irq_of_parse_and_map(np, i);
+ }
+
+ /* If CLINT timer irq not found then fail */
+ if (!clint_timer_irq) {
+ pr_err("%pOFP: timer irq not found\n", np);
+ return -ENODEV;
+ }
+
+ base = of_iomap(np, 0);
+ if (!base) {
+ pr_err("%pOFP: could not map registers\n", np);
+ return -ENODEV;
+ }
+
+ clint_ipi_base = base + CLINT_IPI_OFF;
+ clint_timer_cmp = base + CLINT_TIMER_CMP_OFF;
+ clint_timer_val = base + CLINT_TIMER_VAL_OFF;
+ clint_timer_freq = riscv_timebase;
+
+ pr_info("%pOFP: timer running at %ld Hz\n", np, clint_timer_freq);
+
+ rc = clocksource_register_hz(&clint_clocksource, clint_timer_freq);
+ if (rc) {
+ iounmap(base);
+ pr_err("%pOFP: clocksource register failed [%d]\n", np, rc);
+ return rc;
+ }
+
+ sched_clock_register(clint_sched_clock, 64, clint_timer_freq);
+
+ rc = request_percpu_irq(clint_timer_irq, clint_timer_interrupt,
+ "clint-timer", &clint_clock_event);
+ if (rc) {
+ iounmap(base);
+ pr_err("registering percpu irq failed [%d]\n", rc);
+ return rc;
+ }
+
+ rc = cpuhp_setup_state(CPUHP_AP_CLINT_TIMER_STARTING,
+ "clockevents/clint/timer:starting",
+ clint_timer_starting_cpu,
+ clint_timer_dying_cpu);
+ if (rc) {
+ free_irq(clint_timer_irq, &clint_clock_event);
+ iounmap(base);
+ pr_err("%pOFP: cpuhp setup state failed [%d]\n", np, rc);
+ return rc;
+ }
+
+ riscv_set_ipi_ops(&clint_ipi_ops);
+ clint_clear_ipi();
+
+ return 0;
+}
+
+TIMER_OF_DECLARE(clint_timer, "riscv,clint0", clint_timer_init_dt);
+TIMER_OF_DECLARE(clint_timer1, "sifive,clint0", clint_timer_init_dt);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 191772d4a4d7..1451f4625833 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -132,6 +132,7 @@ enum cpuhp_state {
CPUHP_AP_MIPS_GIC_TIMER_STARTING,
CPUHP_AP_ARC_TIMER_STARTING,
CPUHP_AP_RISCV_TIMER_STARTING,
+ CPUHP_AP_CLINT_TIMER_STARTING,
CPUHP_AP_CSKY_TIMER_STARTING,
CPUHP_AP_HYPERV_TIMER_STARTING,
CPUHP_AP_KVM_STARTING,
--
2.25.1

2020-07-15 07:18:14

by Anup Patel

Subject: [PATCH v3 4/4] dt-bindings: timer: Add CLINT bindings

We add DT bindings documentation for CLINT device.

Signed-off-by: Anup Patel <[email protected]>
Reviewed-by: Palmer Dabbelt <[email protected]>
---
.../bindings/timer/sifive,clint.yaml | 58 +++++++++++++++++++
1 file changed, 58 insertions(+)
create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.yaml

diff --git a/Documentation/devicetree/bindings/timer/sifive,clint.yaml b/Documentation/devicetree/bindings/timer/sifive,clint.yaml
new file mode 100644
index 000000000000..f5579a759ef5
--- /dev/null
+++ b/Documentation/devicetree/bindings/timer/sifive,clint.yaml
@@ -0,0 +1,58 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/timer/sifive,clint.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: SiFive Core Local Interruptor
+
+maintainers:
+ - Palmer Dabbelt <[email protected]>
+ - Anup Patel <[email protected]>
+
+description:
+ SiFive (and other RISC-V) SOCs include an implementation of the SiFive
+ Core Local Interruptor (CLINT) for M-mode timer and M-mode inter-processor
+ interrupts. It directly connects to the timer and inter-processor interrupt
+ lines of various HARTs (or CPUs) so RISC-V per-HART (or per-CPU) local
+ interrupt controller is the parent interrupt controller for CLINT device.
+ The clock frequency of CLINT is specified via "timebase-frequency" DT
+ property of "/cpus" DT node. The "timebase-frequency" DT property is
+ described in Documentation/devicetree/bindings/riscv/cpus.yaml
+
+properties:
+ compatible:
+ items:
+ - const: sifive,fu540-c000-clint
+ - const: sifive,clint0
+
+ description:
+ Should be "sifive,<chip>-clint" and "sifive,clint<version>".
+ Supported compatible strings are -
+ "sifive,fu540-c000-clint" for the SiFive CLINT v0 as integrated
+ onto the SiFive FU540 chip, and "sifive,clint0" for the SiFive
+ CLINT v0 IP block with no chip integration tweaks.
+ Please refer to sifive-blocks-ip-versioning.txt for details
+
+ reg:
+ maxItems: 1
+
+ interrupts-extended:
+ minItems: 1
+
+required:
+ - compatible
+ - reg
+ - interrupts-extended
+
+examples:
+ - |
+ clint@2000000 {
+ compatible = "sifive,clint0", "sifive,fu540-c000-clint";
+ interrupts-extended = <&cpu1-intc 3 &cpu1-intc 7
+ &cpu2-intc 3 &cpu2-intc 7
+ &cpu3-intc 3 &cpu3-intc 7
+ &cpu4-intc 3 &cpu4-intc 7>;
+ reg = <0x2000000 0x4000000>;
+ };
+...
--
2.25.1

2020-07-15 07:18:19

by Anup Patel

Subject: [PATCH v3 3/4] RISC-V: Remove CLINT related code from timer and arch

Right now the RISC-V timer driver is convoluted to support:
1. Linux RISC-V S-mode (with MMU) where it will use TIME CSR for
clocksource and SBI timer calls for clockevent device.
2. Linux RISC-V M-mode (without MMU) where it will use CLINT MMIO
counter register for clocksource and CLINT MMIO compare register
for clockevent device.

We now have a separate CLINT timer driver which also provide CLINT
based IPI operations so let's remove CLINT MMIO related code from
arch/riscv directory and RISC-V timer driver.

Signed-off-by: Anup Patel <[email protected]>
---
arch/riscv/Kconfig | 2 +-
arch/riscv/include/asm/clint.h | 39 ---------------------------
arch/riscv/include/asm/timex.h | 28 +++++---------------
arch/riscv/kernel/Makefile | 2 +-
arch/riscv/kernel/clint.c | 44 -------------------------------
arch/riscv/kernel/setup.c | 2 --
arch/riscv/kernel/smp.c | 1 -
arch/riscv/kernel/smpboot.c | 1 -
drivers/clocksource/Kconfig | 2 +-
drivers/clocksource/timer-riscv.c | 17 ++----------
10 files changed, 12 insertions(+), 126 deletions(-)
delete mode 100644 arch/riscv/include/asm/clint.h
delete mode 100644 arch/riscv/kernel/clint.c

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index fedb4a72b29a..57a72ae23d10 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -74,7 +74,7 @@ config RISCV
select PCI_DOMAINS_GENERIC if PCI
select PCI_MSI if PCI
select RISCV_INTC
- select RISCV_TIMER
+ select RISCV_TIMER if RISCV_SBI
select SPARSEMEM_STATIC if 32BIT
select SPARSE_IRQ
select SYSCTL_EXCEPTION_TRACE
diff --git a/arch/riscv/include/asm/clint.h b/arch/riscv/include/asm/clint.h
deleted file mode 100644
index a279b17a6aad..000000000000
--- a/arch/riscv/include/asm/clint.h
+++ /dev/null
@@ -1,39 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _ASM_RISCV_CLINT_H
-#define _ASM_RISCV_CLINT_H 1
-
-#include <linux/io.h>
-#include <linux/smp.h>
-
-#ifdef CONFIG_RISCV_M_MODE
-extern u32 __iomem *clint_ipi_base;
-
-void clint_init_boot_cpu(void);
-
-static inline void clint_send_ipi_single(unsigned long hartid)
-{
- writel(1, clint_ipi_base + hartid);
-}
-
-static inline void clint_send_ipi_mask(const struct cpumask *mask)
-{
- int cpu;
-
- for_each_cpu(cpu, mask)
- clint_send_ipi_single(cpuid_to_hartid_map(cpu));
-}
-
-static inline void clint_clear_ipi(unsigned long hartid)
-{
- writel(0, clint_ipi_base + hartid);
-}
-#else /* CONFIG_RISCV_M_MODE */
-#define clint_init_boot_cpu() do { } while (0)
-
-/* stubs to for code is only reachable under IS_ENABLED(CONFIG_RISCV_M_MODE): */
-void clint_send_ipi_single(unsigned long hartid);
-void clint_send_ipi_mask(const struct cpumask *hartid_mask);
-void clint_clear_ipi(unsigned long hartid);
-#endif /* CONFIG_RISCV_M_MODE */
-
-#endif /* _ASM_RISCV_CLINT_H */
diff --git a/arch/riscv/include/asm/timex.h b/arch/riscv/include/asm/timex.h
index bad2a7c2cda5..a3fb85d505d4 100644
--- a/arch/riscv/include/asm/timex.h
+++ b/arch/riscv/include/asm/timex.h
@@ -7,41 +7,27 @@
#define _ASM_RISCV_TIMEX_H

#include <asm/csr.h>
-#include <asm/mmio.h>

typedef unsigned long cycles_t;

-extern u64 __iomem *riscv_time_val;
-extern u64 __iomem *riscv_time_cmp;
-
-#ifdef CONFIG_64BIT
-#define mmio_get_cycles() readq_relaxed(riscv_time_val)
-#else
-#define mmio_get_cycles() readl_relaxed(riscv_time_val)
-#define mmio_get_cycles_hi() readl_relaxed(((u32 *)riscv_time_val) + 1)
-#endif
-
static inline cycles_t get_cycles(void)
{
- if (IS_ENABLED(CONFIG_RISCV_SBI))
- return csr_read(CSR_TIME);
- return mmio_get_cycles();
+ return csr_read(CSR_TIME);
}
#define get_cycles get_cycles

+static inline u32 get_cycles_hi(void)
+{
+ return csr_read(CSR_TIMEH);
+}
+#define get_cycles_hi get_cycles_hi
+
#ifdef CONFIG_64BIT
static inline u64 get_cycles64(void)
{
return get_cycles();
}
#else /* CONFIG_64BIT */
-static inline u32 get_cycles_hi(void)
-{
- if (IS_ENABLED(CONFIG_RISCV_SBI))
- return csr_read(CSR_TIMEH);
- return mmio_get_cycles_hi();
-}
-
static inline u64 get_cycles64(void)
{
u32 hi, lo;
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index b355cf485671..7edf15643146 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -31,7 +31,7 @@ obj-y += cacheinfo.o
obj-y += patch.o
obj-$(CONFIG_MMU) += vdso.o vdso/

-obj-$(CONFIG_RISCV_M_MODE) += clint.o traps_misaligned.o
+obj-$(CONFIG_RISCV_M_MODE) += traps_misaligned.o
obj-$(CONFIG_FPU) += fpu.o
obj-$(CONFIG_SMP) += smpboot.o
obj-$(CONFIG_SMP) += smp.o
diff --git a/arch/riscv/kernel/clint.c b/arch/riscv/kernel/clint.c
deleted file mode 100644
index 3647980d14c3..000000000000
--- a/arch/riscv/kernel/clint.c
+++ /dev/null
@@ -1,44 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (c) 2019 Christoph Hellwig.
- */
-
-#include <linux/io.h>
-#include <linux/of_address.h>
-#include <linux/types.h>
-#include <asm/clint.h>
-#include <asm/csr.h>
-#include <asm/timex.h>
-#include <asm/smp.h>
-
-/*
- * This is the layout used by the SiFive clint, which is also shared by the qemu
- * virt platform, and the Kendryte KD210 at least.
- */
-#define CLINT_IPI_OFF 0
-#define CLINT_TIME_CMP_OFF 0x4000
-#define CLINT_TIME_VAL_OFF 0xbff8
-
-u32 __iomem *clint_ipi_base;
-
-void clint_init_boot_cpu(void)
-{
- struct device_node *np;
- void __iomem *base;
-
- np = of_find_compatible_node(NULL, NULL, "riscv,clint0");
- if (!np) {
- panic("clint not found");
- return;
- }
-
- base = of_iomap(np, 0);
- if (!base)
- panic("could not map CLINT");
-
- clint_ipi_base = base + CLINT_IPI_OFF;
- riscv_time_cmp = base + CLINT_TIME_CMP_OFF;
- riscv_time_val = base + CLINT_TIME_VAL_OFF;
-
- clint_clear_ipi(boot_cpu_hartid);
-}
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index f04373be54a6..2c6dd329312b 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -18,7 +18,6 @@
#include <linux/swiotlb.h>
#include <linux/smp.h>

-#include <asm/clint.h>
#include <asm/cpu_ops.h>
#include <asm/setup.h>
#include <asm/sections.h>
@@ -79,7 +78,6 @@ void __init setup_arch(char **cmdline_p)
#else
unflatten_device_tree();
#endif
- clint_init_boot_cpu();

#ifdef CONFIG_SWIOTLB
swiotlb_init(1);
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 8b85683ce203..07626be78c23 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -17,7 +17,6 @@
#include <linux/seq_file.h>
#include <linux/delay.h>

-#include <asm/clint.h>
#include <asm/sbi.h>
#include <asm/tlbflush.h>
#include <asm/cacheflush.h>
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 5fe849791bf0..a6cfa9842d4b 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -24,7 +24,6 @@
#include <linux/of.h>
#include <linux/sched/task_stack.h>
#include <linux/sched/mm.h>
-#include <asm/clint.h>
#include <asm/cpu_ops.h>
#include <asm/irq.h>
#include <asm/mmu_context.h>
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index eabcf1cfb0c0..d3bf66123c4e 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -649,7 +649,7 @@ config ATCPIT100_TIMER

config RISCV_TIMER
bool "Timer for the RISC-V platform"
- depends on GENERIC_SCHED_CLOCK && RISCV
+ depends on GENERIC_SCHED_CLOCK && RISCV_SBI
default y
select TIMER_PROBE
select TIMER_OF
diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index 9de1dabfb126..c51c5ed15aa7 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -19,26 +19,13 @@
#include <linux/of_irq.h>
#include <asm/smp.h>
#include <asm/sbi.h>
-
-u64 __iomem *riscv_time_cmp;
-u64 __iomem *riscv_time_val;
-
-static inline void mmio_set_timer(u64 val)
-{
- void __iomem *r;
-
- r = riscv_time_cmp + cpuid_to_hartid_map(smp_processor_id());
- writeq_relaxed(val, r);
-}
+#include <asm/timex.h>

static int riscv_clock_next_event(unsigned long delta,
struct clock_event_device *ce)
{
csr_set(CSR_IE, IE_TIE);
- if (IS_ENABLED(CONFIG_RISCV_SBI))
- sbi_set_timer(get_cycles64() + delta);
- else
- mmio_set_timer(get_cycles64() + delta);
+ sbi_set_timer(get_cycles64() + delta);
return 0;
}

--
2.25.1

2020-07-15 15:11:30

by Emil Renner Berthing

Subject: Re: [PATCH v3 0/4] Dedicated CLINT timer driver

On Wed, 15 Jul 2020 at 09:15, Anup Patel <[email protected]> wrote:
> The current RISC-V timer driver is convoluted and implements two
> distinct timers:
> 1. S-mode timer: This is for Linux RISC-V S-mode with MMU. The
> clocksource is implemented using TIME CSR and clockevent device
> is implemented using SBI Timer calls.
> 2. M-mode timer: This is for Linux RISC-V M-mode without MMU. The
> clocksource is implemented using CLINT MMIO time register and
> clockevent device is implemented using CLINT MMIO timecmp registers.
>
> This patchset removes clint related code from RISC-V timer driver and
> arch/riscv directory. Instead, the series adds a dedicated MMIO based
> CLINT driver under drivers/clocksource directory which can be used by
> Linux RISC-V M-mode (i.e NoMMU Linux RISC-V).
>
> The patchset is based up Linux-5.8-rc5 and can be found at riscv_clint_v3
> branch of: https://github.com/avpatel/linux.git
>
> This series is tested on:
> 1. QEMU RV64 virt machine using Linux RISC-V S-mode
> 2. QEMU RV32 virt machine using Linux RISC-V S-mode
> 3. QEMU RV64 virt machine using Linux RISC-V M-mode (i.e. NoMMU)
>
> Changes since v2:
> - Rebased series on Linux-5.8-rc5
> - Squashed PATCH3 onto PATCH2 to preserve GIT bisectability
> - Moved PATCH4 before PATCH2 to preserve GIT bisectability
> - Replaced CLINT dt-bindings text document with YAML schema
> - Use SiFive CLINT compatible string as per SiFive IP block versioning
>
> Changes since v1:
> - Rebased series on Linux-5.8-rc2
> - Added pr_warn() for case where ipi_ops not available in PATCH1
> - Updated ipi_inject() prototype to use "struct cpumask *" in PATCH1
> - Updated CLINT_TIMER kconfig option to depend on RISCV_M_MODE in PATCH4
> - Added riscv,clint0 compatible string in DT bindings document
>
> Anup Patel (4):
> RISC-V: Add mechanism to provide custom IPI operations
> clocksource/drivers: Add CLINT timer driver
> RISC-V: Remove CLINT related code from timer and arch
> dt-bindings: timer: Add CLINT bindings
>
> .../bindings/timer/sifive,clint.yaml | 58 +++++
> arch/riscv/Kconfig | 2 +-
> arch/riscv/include/asm/clint.h | 39 ---
> arch/riscv/include/asm/smp.h | 19 ++
> arch/riscv/include/asm/timex.h | 28 +--
> arch/riscv/kernel/Makefile | 2 +-
> arch/riscv/kernel/clint.c | 44 ----
> arch/riscv/kernel/sbi.c | 14 ++
> arch/riscv/kernel/setup.c | 2 -
> arch/riscv/kernel/smp.c | 44 ++--
> arch/riscv/kernel/smpboot.c | 4 +-
> drivers/clocksource/Kconfig | 12 +-
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/timer-clint.c | 229 ++++++++++++++++++
> drivers/clocksource/timer-riscv.c | 17 +-
> include/linux/cpuhotplug.h | 1 +
> 16 files changed, 369 insertions(+), 147 deletions(-)
> create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.yaml
> delete mode 100644 arch/riscv/include/asm/clint.h
> delete mode 100644 arch/riscv/kernel/clint.c
> create mode 100644 drivers/clocksource/timer-clint.c

If it makes any difference I tested this both in Qemu and on the
HiFive Unleashed,
but I don't have a working no-mmu setup.

Tested-by: Emil Renner Berhing <[email protected]>

/Emil

2020-07-15 17:51:51

by Rob Herring (Arm)

Subject: Re: [PATCH v3 4/4] dt-bindings: timer: Add CLINT bindings

On Wed, 15 Jul 2020 12:45:05 +0530, Anup Patel wrote:
> We add DT bindings documentation for CLINT device.
>
> Signed-off-by: Anup Patel <[email protected]>
> Reviewed-by: Palmer Dabbelt <[email protected]>
> ---
> .../bindings/timer/sifive,clint.yaml | 58 +++++++++++++++++++
> 1 file changed, 58 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.yaml
>


My bot found errors running 'make dt_binding_check' on your patch:

Error: Documentation/devicetree/bindings/timer/sifive,clint.example.dts:21.39-40 syntax error
FATAL ERROR: Unable to parse input tree
scripts/Makefile.lib:315: recipe for target 'Documentation/devicetree/bindings/timer/sifive,clint.example.dt.yaml' failed
make[1]: *** [Documentation/devicetree/bindings/timer/sifive,clint.example.dt.yaml] Error 1
make[1]: *** Waiting for unfinished jobs....
Makefile:1347: recipe for target 'dt_binding_check' failed
make: *** [dt_binding_check] Error 2


See https://patchwork.ozlabs.org/patch/1329276

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure dt-schema is up to date:

pip3 install git+https://github.com/devicetree-org/dt-schema.git@master --upgrade

Please check and re-submit.

2020-07-16 12:35:45

by Anup Patel

Subject: Re: [PATCH v3 4/4] dt-bindings: timer: Add CLINT bindings

On Wed, Jul 15, 2020 at 11:20 PM Rob Herring <[email protected]> wrote:
>
> On Wed, 15 Jul 2020 12:45:05 +0530, Anup Patel wrote:
> > We add DT bindings documentation for CLINT device.
> >
> > Signed-off-by: Anup Patel <[email protected]>
> > Reviewed-by: Palmer Dabbelt <[email protected]>
> > ---
> > .../bindings/timer/sifive,clint.yaml | 58 +++++++++++++++++++
> > 1 file changed, 58 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/timer/sifive,clint.yaml
> >
>
>
> My bot found errors running 'make dt_binding_check' on your patch:
>
> Error: Documentation/devicetree/bindings/timer/sifive,clint.example.dts:21.39-40 syntax error
> FATAL ERROR: Unable to parse input tree
> scripts/Makefile.lib:315: recipe for target 'Documentation/devicetree/bindings/timer/sifive,clint.example.dt.yaml' failed
> make[1]: *** [Documentation/devicetree/bindings/timer/sifive,clint.example.dt.yaml] Error 1
> make[1]: *** Waiting for unfinished jobs....
> Makefile:1347: recipe for target 'dt_binding_check' failed
> make: *** [dt_binding_check] Error 2
>
>
> See https://patchwork.ozlabs.org/patch/1329276
>
> If you already ran 'make dt_binding_check' and didn't see the above
> error(s), then make sure dt-schema is up to date:
>
> pip3 install git+https://github.com/devicetree-org/dt-schema.git@master --upgrade
>
> Please check and re-submit.
>

Thanks for these steps. I will fix and send v4.

Regards,
Anup

2020-07-16 14:05:51

by Daniel Lezcano

Subject: Re: [PATCH v3 4/4] dt-bindings: timer: Add CLINT bindings

Hi Anup,


On 16/07/2020 14:32, Anup Patel wrote:
> On Wed, Jul 15, 2020 at 11:20 PM Rob Herring <[email protected]> wrote:

[ ... ]

> Thanks for these steps. I will fix and send v4.

Please take the opportunity to clarify how you want the series to be merged.


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2020-07-16 15:55:46

by Anup Patel

Subject: Re: [PATCH v3 4/4] dt-bindings: timer: Add CLINT bindings

Hi Daniel,

On Thu, Jul 16, 2020 at 7:31 PM Daniel Lezcano
<[email protected]> wrote:
>
>
> Hi Anup,
>
>
> On 16/07/2020 14:32, Anup Patel wrote:
> > On Wed, Jul 15, 2020 at 11:20 PM Rob Herring <[email protected]> wrote:
>
> [ ... ]
>
> > Thanks for these steps. I will fix and send v4.
>
> Please take the opportunity to clarify how you want the series to be merged.

This is yet another series which largely impacts arch/riscv because we are
factoring CLINT code from arch/riscv into it's own timer driver.

I think this can go via the RISC-V tree.

Regards,
Anup

2020-07-16 21:29:06

by Daniel Lezcano

Subject: Re: [PATCH v3 2/4] clocksource/drivers: Add CLINT timer driver

Hi Anup,


On 15/07/2020 09:15, Anup Patel wrote:
> The TIME CSR and SBI calls are not available in RISC-V M-mode so we
> separate add CLINT driver for Linux RISC-V M-mode (i.e. RISC-V NoMMU
> kernel).

The description is confusing, please reword it and give a bit more
information about the timer itself, especially, the IPI thing.

> Signed-off-by: Anup Patel <[email protected]>
> ---
> drivers/clocksource/Kconfig | 10 ++
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/timer-clint.c | 229 ++++++++++++++++++++++++++++++
> include/linux/cpuhotplug.h | 1 +
> 4 files changed, 241 insertions(+)
> create mode 100644 drivers/clocksource/timer-clint.c
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 91418381fcd4..eabcf1cfb0c0 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -658,6 +658,16 @@ config RISCV_TIMER
> is accessed via both the SBI and the rdcycle instruction. This is
> required for all RISC-V systems.
>
> +config CLINT_TIMER
> + bool "Timer for the RISC-V platform"
> + depends on GENERIC_SCHED_CLOCK && RISCV_M_MODE
> + default y
> + select TIMER_PROBE
> + select TIMER_OF
> + help
> + This option enables the CLINT timer for RISC-V systems. The CLINT
> + driver is usually used for NoMMU RISC-V systems.

For the timer, we do silent option and let the platform config select
it. Please refer to other timer option below as reference.

> config CSKY_MP_TIMER
> bool "SMP Timer for the C-SKY platform" if COMPILE_TEST
> depends on CSKY
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index bdda1a2e4097..18e700e703a0 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -87,6 +87,7 @@ obj-$(CONFIG_CLKSRC_ST_LPC) += clksrc_st_lpc.o
> obj-$(CONFIG_X86_NUMACHIP) += numachip.o
> obj-$(CONFIG_ATCPIT100_TIMER) += timer-atcpit100.o
> obj-$(CONFIG_RISCV_TIMER) += timer-riscv.o
> +obj-$(CONFIG_CLINT_TIMER) += timer-clint.o
> obj-$(CONFIG_CSKY_MP_TIMER) += timer-mp-csky.o
> obj-$(CONFIG_GX6605S_TIMER) += timer-gx6605s.o
> obj-$(CONFIG_HYPERV_TIMER) += hyperv_timer.o
> diff --git a/drivers/clocksource/timer-clint.c b/drivers/clocksource/timer-clint.c
> new file mode 100644
> index 000000000000..bfc38bb5a589
> --- /dev/null
> +++ b/drivers/clocksource/timer-clint.c
> @@ -0,0 +1,229 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2020 Western Digital Corporation or its affiliates.
> + *
> + * Most of the M-mode (i.e. NoMMU) RISC-V systems usually have a
> + * CLINT MMIO timer device.
> + */
> +
> +#define pr_fmt(fmt) "clint: " fmt
> +#include <linux/bitops.h>
> +#include <linux/clocksource.h>
> +#include <linux/clockchips.h>
> +#include <linux/cpu.h>
> +#include <linux/delay.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/sched_clock.h>
> +#include <linux/io-64-nonatomic-lo-hi.h>
> +#include <linux/interrupt.h>
> +#include <linux/of_irq.h>
> +#include <linux/smp.h>
> +
> +#define CLINT_IPI_OFF 0
> +#define CLINT_TIMER_CMP_OFF 0x4000
> +#define CLINT_TIMER_VAL_OFF 0xbff8
> +
> +/* CLINT manages IPI and Timer for RISC-V M-mode */
> +static u32 __iomem *clint_ipi_base;
> +static u64 __iomem *clint_timer_cmp;
> +static u64 __iomem *clint_timer_val;
> +static unsigned long clint_timer_freq;
> +static unsigned int clint_timer_irq;
> +
> +static void clint_send_ipi(const struct cpumask *target)
> +{
> + unsigned int cpu;
> +
> + for_each_cpu(cpu, target)
> + writel(1, clint_ipi_base + cpuid_to_hartid_map(cpu));
> +}
> +
> +static void clint_clear_ipi(void)
> +{
> + writel(0, clint_ipi_base + cpuid_to_hartid_map(smp_processor_id()));
> +}
> +
> +static struct riscv_ipi_ops clint_ipi_ops = {
> + .ipi_inject = clint_send_ipi,
> + .ipi_clear = clint_clear_ipi,
> +};
> +
> +#ifdef CONFIG_64BIT
> +#define clint_get_cycles() readq_relaxed(clint_timer_val)
> +#else
> +#define clint_get_cycles() readl_relaxed(clint_timer_val)
> +#define clint_get_cycles_hi() readl_relaxed(((u32 *)clint_timer_val) + 1)
> +#endif
> +
> +#ifdef CONFIG_64BIT
> +static u64 clint_get_cycles64(void)
> +{
> + return clint_get_cycles();
> +}
> +#else /* CONFIG_64BIT */
> +static u64 clint_get_cycles64(void)
> +{
> + u32 hi, lo;
> +
> + do {
> + hi = clint_get_cycles_hi();
> + lo = clint_get_cycles();
> + } while (hi != clint_get_cycles_hi());
> +
> + return ((u64)hi << 32) | lo;
> +}
> +#endif /* CONFIG_64BIT */
> +static int clint_clock_next_event(unsigned long delta,
> + struct clock_event_device *ce)
> +{
> + void __iomem *r = clint_timer_cmp +
> + cpuid_to_hartid_map(smp_processor_id());
> +
> + csr_set(CSR_IE, IE_TIE);
> + writeq_relaxed(clint_get_cycles64() + delta, r);
> + return 0;
> +}
> +
> +static DEFINE_PER_CPU(struct clock_event_device, clint_clock_event) = {
> + .name = "clint_clockevent",
> + .features = CLOCK_EVT_FEAT_ONESHOT,
> + .rating = 100,
> + .set_next_event = clint_clock_next_event,
> +};
> +
> +static u64 clint_rdtime(struct clocksource *cs)
> +{
> + return readq_relaxed(clint_timer_val);
> +}
> +
> +static u64 notrace clint_sched_clock(void)
> +{
> + return readq_relaxed(clint_timer_val);
> +}
> +
> +static struct clocksource clint_clocksource = {
> + .name = "clint_clocksource",
> + .rating = 300,
> + .mask = CLOCKSOURCE_MASK(64),
> + .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> + .read = clint_rdtime,

What if !CONFIG_64BIT

> +};
> +
> +static int clint_timer_starting_cpu(unsigned int cpu)
> +{
> + struct clock_event_device *ce = per_cpu_ptr(&clint_clock_event, cpu);
> +
> + ce->cpumask = cpumask_of(cpu);
> + clockevents_config_and_register(ce, clint_timer_freq, 200, ULONG_MAX);

The function is not immune against registering the same clockevents. If
the CPU is hotplugged several times, this function will be called again
and again. Why not rely on a for_each_possible_cpu loop in the init
function ?

> + enable_percpu_irq(clint_timer_irq,
> + irq_get_trigger_type(clint_timer_irq));

Why do you want to enable / disable the interrrupts ? The should be
already handle by the hotplug framework no ?

> + return 0;
> +}
> +
> +static int clint_timer_dying_cpu(unsigned int cpu)
> +{
> + disable_percpu_irq(clint_timer_irq);
> + return 0;
> +}
> +
> +static irqreturn_t clint_timer_interrupt(int irq, void *dev_id)
> +{
> + struct clock_event_device *evdev = this_cpu_ptr(&clint_clock_event);
> +
> + csr_clear(CSR_IE, IE_TIE);
> + evdev->event_handler(evdev);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static int __init clint_timer_init_dt(struct device_node *np)
> +{
> + int rc;
> + u32 i, nr_irqs;
> + void __iomem *base;
> + struct of_phandle_args oirq;
> +
> + /*
> + * Ensure that CLINT device interrupts are either RV_IRQ_TIMER or
> + * RV_IRQ_SOFT. If it's anything else then we ignore the device.
> + */
> + nr_irqs = of_irq_count(np);
> + for (i = 0; i < nr_irqs; i++) {
> + if (of_irq_parse_one(np, i, &oirq)) {
> + pr_err("%pOFP: failed to parse irq %d.\n", np, i);
> + continue;
> + }
> +
> + if ((oirq.args_count != 1) ||
> + (oirq.args[0] != RV_IRQ_TIMER &&
> + oirq.args[0] != RV_IRQ_SOFT)) {
> + pr_err("%pOFP: invalid irq %d (hwirq %d)\n",
> + np, i, oirq.args[0]);
> + return -ENODEV;
> + }
> +
> + /* Find parent irq domain and map timer irq */
> + if (!clint_timer_irq &&
> + oirq.args[0] == RV_IRQ_TIMER &&
> + irq_find_host(oirq.np))
> + clint_timer_irq = irq_of_parse_and_map(np, i);
> + }
> +
> + /* If CLINT timer irq not found then fail */
> + if (!clint_timer_irq) {
> + pr_err("%pOFP: timer irq not found\n", np);
> + return -ENODEV;
> + }
> +
> + base = of_iomap(np, 0);
> + if (!base) {
> + pr_err("%pOFP: could not map registers\n", np);
> + return -ENODEV;
> + }
> +
> + clint_ipi_base = base + CLINT_IPI_OFF;
> + clint_timer_cmp = base + CLINT_TIMER_CMP_OFF;
> + clint_timer_val = base + CLINT_TIMER_VAL_OFF;
> + clint_timer_freq = riscv_timebase;
> +
> + pr_info("%pOFP: timer running at %ld Hz\n", np, clint_timer_freq);
> +
> + rc = clocksource_register_hz(&clint_clocksource, clint_timer_freq);
> + if (rc) {
> + iounmap(base);
> + pr_err("%pOFP: clocksource register failed [%d]\n", np, rc);
> + return rc;
> + }
> +
> + sched_clock_register(clint_sched_clock, 64, clint_timer_freq);
> +
> + rc = request_percpu_irq(clint_timer_irq, clint_timer_interrupt,
> + "clint-timer", &clint_clock_event);
> + if (rc) {
> + iounmap(base);
> + pr_err("registering percpu irq failed [%d]\n", rc);
> + return rc;
> + }
> +
> + rc = cpuhp_setup_state(CPUHP_AP_CLINT_TIMER_STARTING,
> + "clockevents/clint/timer:starting",
> + clint_timer_starting_cpu,
> + clint_timer_dying_cpu);
> + if (rc) {
> + free_irq(clint_timer_irq, &clint_clock_event);
> + iounmap(base);
> + pr_err("%pOFP: cpuhp setup state failed [%d]\n", np, rc);
> + return rc;
> + }
> +
> + riscv_set_ipi_ops(&clint_ipi_ops);
> + clint_clear_ipi();
> +
> + return 0;
> +}
> +
> +TIMER_OF_DECLARE(clint_timer, "riscv,clint0", clint_timer_init_dt);
> +TIMER_OF_DECLARE(clint_timer1, "sifive,clint0", clint_timer_init_dt);
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 191772d4a4d7..1451f4625833 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -132,6 +132,7 @@ enum cpuhp_state {
> CPUHP_AP_MIPS_GIC_TIMER_STARTING,
> CPUHP_AP_ARC_TIMER_STARTING,
> CPUHP_AP_RISCV_TIMER_STARTING,
> + CPUHP_AP_CLINT_TIMER_STARTING,
> CPUHP_AP_CSKY_TIMER_STARTING,
> CPUHP_AP_HYPERV_TIMER_STARTING,
> CPUHP_AP_KVM_STARTING,
>


--
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2020-07-17 05:22:19

by Anup Patel

Subject: Re: [PATCH v3 2/4] clocksource/drivers: Add CLINT timer driver

On Fri, Jul 17, 2020 at 2:57 AM Daniel Lezcano
<[email protected]> wrote:
>
>
> Hi Anup,
>
>
> On 15/07/2020 09:15, Anup Patel wrote:
> > The TIME CSR and SBI calls are not available in RISC-V M-mode so we
> > separate add CLINT driver for Linux RISC-V M-mode (i.e. RISC-V NoMMU
> > kernel).
>
> The description is confusing, please reword it and give a bit more
> information about the timer itself, especially, the IPI thing.

Okay, will update.

>
> > Signed-off-by: Anup Patel <[email protected]>
> > ---
> > drivers/clocksource/Kconfig | 10 ++
> > drivers/clocksource/Makefile | 1 +
> > drivers/clocksource/timer-clint.c | 229 ++++++++++++++++++++++++++++++
> > include/linux/cpuhotplug.h | 1 +
> > 4 files changed, 241 insertions(+)
> > create mode 100644 drivers/clocksource/timer-clint.c
> >
> > diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> > index 91418381fcd4..eabcf1cfb0c0 100644
> > --- a/drivers/clocksource/Kconfig
> > +++ b/drivers/clocksource/Kconfig
> > @@ -658,6 +658,16 @@ config RISCV_TIMER
> > is accessed via both the SBI and the rdcycle instruction. This is
> > required for all RISC-V systems.
> >
> > +config CLINT_TIMER
> > + bool "Timer for the RISC-V platform"
> > + depends on GENERIC_SCHED_CLOCK && RISCV_M_MODE
> > + default y
> > + select TIMER_PROBE
> > + select TIMER_OF
> > + help
> > + This option enables the CLINT timer for RISC-V systems. The CLINT
> > + driver is usually used for NoMMU RISC-V systems.
>
> For the timer, we do silent option and let the platform config select
> it. Please refer to other timer option below as reference.

Okay, I will use "default RISCV" instead of "default y" (just like other
timer Kconfig options).

>
> > config CSKY_MP_TIMER
> > bool "SMP Timer for the C-SKY platform" if COMPILE_TEST
> > depends on CSKY
> > diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> > index bdda1a2e4097..18e700e703a0 100644
> > --- a/drivers/clocksource/Makefile
> > +++ b/drivers/clocksource/Makefile
> > @@ -87,6 +87,7 @@ obj-$(CONFIG_CLKSRC_ST_LPC) += clksrc_st_lpc.o
> > obj-$(CONFIG_X86_NUMACHIP) += numachip.o
> > obj-$(CONFIG_ATCPIT100_TIMER) += timer-atcpit100.o
> > obj-$(CONFIG_RISCV_TIMER) += timer-riscv.o
> > +obj-$(CONFIG_CLINT_TIMER) += timer-clint.o
> > obj-$(CONFIG_CSKY_MP_TIMER) += timer-mp-csky.o
> > obj-$(CONFIG_GX6605S_TIMER) += timer-gx6605s.o
> > obj-$(CONFIG_HYPERV_TIMER) += hyperv_timer.o
> > diff --git a/drivers/clocksource/timer-clint.c b/drivers/clocksource/timer-clint.c
> > new file mode 100644
> > index 000000000000..bfc38bb5a589
> > --- /dev/null
> > +++ b/drivers/clocksource/timer-clint.c
> > @@ -0,0 +1,229 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (C) 2020 Western Digital Corporation or its affiliates.
> > + *
> > + * Most of the M-mode (i.e. NoMMU) RISC-V systems usually have a
> > + * CLINT MMIO timer device.
> > + */
> > +
> > +#define pr_fmt(fmt) "clint: " fmt
> > +#include <linux/bitops.h>
> > +#include <linux/clocksource.h>
> > +#include <linux/clockchips.h>
> > +#include <linux/cpu.h>
> > +#include <linux/delay.h>
> > +#include <linux/module.h>
> > +#include <linux/of_address.h>
> > +#include <linux/sched_clock.h>
> > +#include <linux/io-64-nonatomic-lo-hi.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/of_irq.h>
> > +#include <linux/smp.h>
> > +
> > +#define CLINT_IPI_OFF 0
> > +#define CLINT_TIMER_CMP_OFF 0x4000
> > +#define CLINT_TIMER_VAL_OFF 0xbff8
> > +
> > +/* CLINT manages IPI and Timer for RISC-V M-mode */
> > +static u32 __iomem *clint_ipi_base;
> > +static u64 __iomem *clint_timer_cmp;
> > +static u64 __iomem *clint_timer_val;
> > +static unsigned long clint_timer_freq;
> > +static unsigned int clint_timer_irq;
> > +
> > +static void clint_send_ipi(const struct cpumask *target)
> > +{
> > + unsigned int cpu;
> > +
> > + for_each_cpu(cpu, target)
> > + writel(1, clint_ipi_base + cpuid_to_hartid_map(cpu));
> > +}
> > +
> > +static void clint_clear_ipi(void)
> > +{
> > + writel(0, clint_ipi_base + cpuid_to_hartid_map(smp_processor_id()));
> > +}
> > +
> > +static struct riscv_ipi_ops clint_ipi_ops = {
> > + .ipi_inject = clint_send_ipi,
> > + .ipi_clear = clint_clear_ipi,
> > +};
> > +
> > +#ifdef CONFIG_64BIT
> > +#define clint_get_cycles() readq_relaxed(clint_timer_val)
> > +#else
> > +#define clint_get_cycles() readl_relaxed(clint_timer_val)
> > +#define clint_get_cycles_hi() readl_relaxed(((u32 *)clint_timer_val) + 1)
> > +#endif
> > +
> > +#ifdef CONFIG_64BIT
> > +static u64 clint_get_cycles64(void)
> > +{
> > + return clint_get_cycles();
> > +}
> > +#else /* CONFIG_64BIT */
> > +static u64 clint_get_cycles64(void)
> > +{
> > + u32 hi, lo;
> > +
> > + do {
> > + hi = clint_get_cycles_hi();
> > + lo = clint_get_cycles();
> > + } while (hi != clint_get_cycles_hi());
> > +
> > + return ((u64)hi << 32) | lo;
> > +}
> > +#endif /* CONFIG_64BIT */
> > +static int clint_clock_next_event(unsigned long delta,
> > + struct clock_event_device *ce)
> > +{
> > + void __iomem *r = clint_timer_cmp +
> > + cpuid_to_hartid_map(smp_processor_id());
> > +
> > + csr_set(CSR_IE, IE_TIE);
> > + writeq_relaxed(clint_get_cycles64() + delta, r);
> > + return 0;
> > +}
> > +
> > +static DEFINE_PER_CPU(struct clock_event_device, clint_clock_event) = {
> > + .name = "clint_clockevent",
> > + .features = CLOCK_EVT_FEAT_ONESHOT,
> > + .rating = 100,
> > + .set_next_event = clint_clock_next_event,
> > +};
> > +
> > +static u64 clint_rdtime(struct clocksource *cs)
> > +{
> > + return readq_relaxed(clint_timer_val);
> > +}
> > +
> > +static u64 notrace clint_sched_clock(void)
> > +{
> > + return readq_relaxed(clint_timer_val);
> > +}
> > +
> > +static struct clocksource clint_clocksource = {
> > + .name = "clint_clocksource",
> > + .rating = 300,
> > + .mask = CLOCKSOURCE_MASK(64),
> > + .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> > + .read = clint_rdtime,
>
> What if !CONFIG_64BIT

The CLINT counter is 64bit for both 32bit and 64bit systems
but I should have used clint_get_cycles64() in clint_rdtime().
I will update it.

>
> > +};
> > +
> > +static int clint_timer_starting_cpu(unsigned int cpu)
> > +{
> > + struct clock_event_device *ce = per_cpu_ptr(&clint_clock_event, cpu);
> > +
> > + ce->cpumask = cpumask_of(cpu);
> > + clockevents_config_and_register(ce, clint_timer_freq, 200, ULONG_MAX);
>
> The function is not immune against registering the same clockevents. If
> the CPU is hotplugged several times, this function will be called again
> and again. Why not rely on a for_each_possible_cpu loop in the init
> function ?
>
> > + enable_percpu_irq(clint_timer_irq,
> > + irq_get_trigger_type(clint_timer_irq));
>
> Why do you want to enable / disable the interrrupts ? The should be
> already handle by the hotplug framework no ?

The perCPU interrupts are not enabled by default. We have to
explicitly enable/disable perCPU interrupts in CPU hotplug callbacks.

>
> > + return 0;
> > +}
> > +
> > +static int clint_timer_dying_cpu(unsigned int cpu)
> > +{
> > + disable_percpu_irq(clint_timer_irq);
> > + return 0;
> > +}
> > +
> > +static irqreturn_t clint_timer_interrupt(int irq, void *dev_id)
> > +{
> > + struct clock_event_device *evdev = this_cpu_ptr(&clint_clock_event);
> > +
> > + csr_clear(CSR_IE, IE_TIE);
> > + evdev->event_handler(evdev);
> > +
> > + return IRQ_HANDLED;
> > +}
> > +
> > +static int __init clint_timer_init_dt(struct device_node *np)
> > +{
> > + int rc;
> > + u32 i, nr_irqs;
> > + void __iomem *base;
> > + struct of_phandle_args oirq;
> > +
> > + /*
> > + * Ensure that CLINT device interrupts are either RV_IRQ_TIMER or
> > + * RV_IRQ_SOFT. If it's anything else then we ignore the device.
> > + */
> > + nr_irqs = of_irq_count(np);
> > + for (i = 0; i < nr_irqs; i++) {
> > + if (of_irq_parse_one(np, i, &oirq)) {
> > + pr_err("%pOFP: failed to parse irq %d.\n", np, i);
> > + continue;
> > + }
> > +
> > + if ((oirq.args_count != 1) ||
> > + (oirq.args[0] != RV_IRQ_TIMER &&
> > + oirq.args[0] != RV_IRQ_SOFT)) {
> > + pr_err("%pOFP: invalid irq %d (hwirq %d)\n",
> > + np, i, oirq.args[0]);
> > + return -ENODEV;
> > + }
> > +
> > + /* Find parent irq domain and map timer irq */
> > + if (!clint_timer_irq &&
> > + oirq.args[0] == RV_IRQ_TIMER &&
> > + irq_find_host(oirq.np))
> > + clint_timer_irq = irq_of_parse_and_map(np, i);
> > + }
> > +
> > + /* If CLINT timer irq not found then fail */
> > + if (!clint_timer_irq) {
> > + pr_err("%pOFP: timer irq not found\n", np);
> > + return -ENODEV;
> > + }
> > +
> > + base = of_iomap(np, 0);
> > + if (!base) {
> > + pr_err("%pOFP: could not map registers\n", np);
> > + return -ENODEV;
> > + }
> > +
> > + clint_ipi_base = base + CLINT_IPI_OFF;
> > + clint_timer_cmp = base + CLINT_TIMER_CMP_OFF;
> > + clint_timer_val = base + CLINT_TIMER_VAL_OFF;
> > + clint_timer_freq = riscv_timebase;
> > +
> > + pr_info("%pOFP: timer running at %ld Hz\n", np, clint_timer_freq);
> > +
> > + rc = clocksource_register_hz(&clint_clocksource, clint_timer_freq);
> > + if (rc) {
> > + iounmap(base);
> > + pr_err("%pOFP: clocksource register failed [%d]\n", np, rc);
> > + return rc;
> > + }
> > +
> > + sched_clock_register(clint_sched_clock, 64, clint_timer_freq);
> > +
> > + rc = request_percpu_irq(clint_timer_irq, clint_timer_interrupt,
> > + "clint-timer", &clint_clock_event);
> > + if (rc) {
> > + iounmap(base);
> > + pr_err("registering percpu irq failed [%d]\n", rc);
> > + return rc;
> > + }
> > +
> > + rc = cpuhp_setup_state(CPUHP_AP_CLINT_TIMER_STARTING,
> > + "clockevents/clint/timer:starting",
> > + clint_timer_starting_cpu,
> > + clint_timer_dying_cpu);
> > + if (rc) {
> > + free_irq(clint_timer_irq, &clint_clock_event);
> > + iounmap(base);
> > + pr_err("%pOFP: cpuhp setup state failed [%d]\n", np, rc);
> > + return rc;
> > + }
> > +
> > + riscv_set_ipi_ops(&clint_ipi_ops);
> > + clint_clear_ipi();
> > +
> > + return 0;
> > +}
> > +
> > +TIMER_OF_DECLARE(clint_timer, "riscv,clint0", clint_timer_init_dt);
> > +TIMER_OF_DECLARE(clint_timer1, "sifive,clint0", clint_timer_init_dt);
> > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> > index 191772d4a4d7..1451f4625833 100644
> > --- a/include/linux/cpuhotplug.h
> > +++ b/include/linux/cpuhotplug.h
> > @@ -132,6 +132,7 @@ enum cpuhp_state {
> > CPUHP_AP_MIPS_GIC_TIMER_STARTING,
> > CPUHP_AP_ARC_TIMER_STARTING,
> > CPUHP_AP_RISCV_TIMER_STARTING,
> > + CPUHP_AP_CLINT_TIMER_STARTING,
> > CPUHP_AP_CSKY_TIMER_STARTING,
> > CPUHP_AP_HYPERV_TIMER_STARTING,
> > CPUHP_AP_KVM_STARTING,
> >
>
>
> --
> <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
>
> Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook |
> <http://twitter.com/#!/linaroorg> Twitter |
> <http://www.linaro.org/linaro-blog/> Blog

Regards,
Anup

2020-07-17 05:29:44

by Daniel Lezcano

Subject: Re: [PATCH v3 2/4] clocksource/drivers: Add CLINT timer driver

On 17/07/2020 07:21, Anup Patel wrote:
> On Fri, Jul 17, 2020 at 2:57 AM Daniel Lezcano
> <[email protected]> wrote:
>>
>>
>> Hi Anup,
>>
>>
>> On 15/07/2020 09:15, Anup Patel wrote:
>>> The TIME CSR and SBI calls are not available in RISC-V M-mode so we
>>> separate add CLINT driver for Linux RISC-V M-mode (i.e. RISC-V NoMMU
>>> kernel).
>>
>> The description is confusing, please reword it and give a bit more
>> information about the timer itself, especially, the IPI thing.
>
> Okay, will update.
>
>>
>>> Signed-off-by: Anup Patel <[email protected]>
>>> ---
>>> drivers/clocksource/Kconfig | 10 ++
>>> drivers/clocksource/Makefile | 1 +
>>> drivers/clocksource/timer-clint.c | 229 ++++++++++++++++++++++++++++++
>>> include/linux/cpuhotplug.h | 1 +
>>> 4 files changed, 241 insertions(+)
>>> create mode 100644 drivers/clocksource/timer-clint.c
>>>
>>> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
>>> index 91418381fcd4..eabcf1cfb0c0 100644
>>> --- a/drivers/clocksource/Kconfig
>>> +++ b/drivers/clocksource/Kconfig
>>> @@ -658,6 +658,16 @@ config RISCV_TIMER
>>> is accessed via both the SBI and the rdcycle instruction. This is
>>> required for all RISC-V systems.
>>>
>>> +config CLINT_TIMER
>>> + bool "Timer for the RISC-V platform"
>>> + depends on GENERIC_SCHED_CLOCK && RISCV_M_MODE
>>> + default y
>>> + select TIMER_PROBE
>>> + select TIMER_OF
>>> + help
>>> + This option enables the CLINT timer for RISC-V systems. The CLINT
>>> + driver is usually used for NoMMU RISC-V systems.
>>
>> For the timer, we do silent option and let the platform config select
>> it. Please refer to other timer option below as reference.
>
> Okay, I will use "default RISCV" instead of "default y" (just like other
> timer Kconfig options).

Preferably, select it from the platform's Kconfig.

>>
>>> config CSKY_MP_TIMER
>>> bool "SMP Timer for the C-SKY platform" if COMPILE_TEST
>>> depends on CSKY
>>> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
>>> index bdda1a2e4097..18e700e703a0 100644
>>> --- a/drivers/clocksource/Makefile
>>> +++ b/drivers/clocksource/Makefile
>>> @@ -87,6 +87,7 @@ obj-$(CONFIG_CLKSRC_ST_LPC) += clksrc_st_lpc.o
>>> obj-$(CONFIG_X86_NUMACHIP) += numachip.o
>>> obj-$(CONFIG_ATCPIT100_TIMER) += timer-atcpit100.o
>>> obj-$(CONFIG_RISCV_TIMER) += timer-riscv.o
>>> +obj-$(CONFIG_CLINT_TIMER) += timer-clint.o
>>> obj-$(CONFIG_CSKY_MP_TIMER) += timer-mp-csky.o
>>> obj-$(CONFIG_GX6605S_TIMER) += timer-gx6605s.o
>>> obj-$(CONFIG_HYPERV_TIMER) += hyperv_timer.o
>>> diff --git a/drivers/clocksource/timer-clint.c b/drivers/clocksource/timer-clint.c
>>> new file mode 100644
>>> index 000000000000..bfc38bb5a589
>>> --- /dev/null
>>> +++ b/drivers/clocksource/timer-clint.c
>>> @@ -0,0 +1,229 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * Copyright (C) 2020 Western Digital Corporation or its affiliates.
>>> + *
>>> + * Most of the M-mode (i.e. NoMMU) RISC-V systems usually have a
>>> + * CLINT MMIO timer device.
>>> + */
>>> +
>>> +#define pr_fmt(fmt) "clint: " fmt
>>> +#include <linux/bitops.h>
>>> +#include <linux/clocksource.h>
>>> +#include <linux/clockchips.h>
>>> +#include <linux/cpu.h>
>>> +#include <linux/delay.h>
>>> +#include <linux/module.h>
>>> +#include <linux/of_address.h>
>>> +#include <linux/sched_clock.h>
>>> +#include <linux/io-64-nonatomic-lo-hi.h>
>>> +#include <linux/interrupt.h>
>>> +#include <linux/of_irq.h>
>>> +#include <linux/smp.h>
>>> +
>>> +#define CLINT_IPI_OFF 0
>>> +#define CLINT_TIMER_CMP_OFF 0x4000
>>> +#define CLINT_TIMER_VAL_OFF 0xbff8
>>> +
>>> +/* CLINT manages IPI and Timer for RISC-V M-mode */
>>> +static u32 __iomem *clint_ipi_base;
>>> +static u64 __iomem *clint_timer_cmp;
>>> +static u64 __iomem *clint_timer_val;
>>> +static unsigned long clint_timer_freq;
>>> +static unsigned int clint_timer_irq;
>>> +
>>> +static void clint_send_ipi(const struct cpumask *target)
>>> +{
>>> + unsigned int cpu;
>>> +
>>> + for_each_cpu(cpu, target)
>>> + writel(1, clint_ipi_base + cpuid_to_hartid_map(cpu));
>>> +}
>>> +
>>> +static void clint_clear_ipi(void)
>>> +{
>>> + writel(0, clint_ipi_base + cpuid_to_hartid_map(smp_processor_id()));
>>> +}
>>> +
>>> +static struct riscv_ipi_ops clint_ipi_ops = {
>>> + .ipi_inject = clint_send_ipi,
>>> + .ipi_clear = clint_clear_ipi,
>>> +};
>>> +
>>> +#ifdef CONFIG_64BIT
>>> +#define clint_get_cycles() readq_relaxed(clint_timer_val)
>>> +#else
>>> +#define clint_get_cycles() readl_relaxed(clint_timer_val)
>>> +#define clint_get_cycles_hi() readl_relaxed(((u32 *)clint_timer_val) + 1)
>>> +#endif
>>> +
>>> +#ifdef CONFIG_64BIT
>>> +static u64 clint_get_cycles64(void)
>>> +{
>>> + return clint_get_cycles();
>>> +}
>>> +#else /* CONFIG_64BIT */
>>> +static u64 clint_get_cycles64(void)
>>> +{
>>> + u32 hi, lo;
>>> +
>>> + do {
>>> + hi = clint_get_cycles_hi();
>>> + lo = clint_get_cycles();
>>> + } while (hi != clint_get_cycles_hi());
>>> +
>>> + return ((u64)hi << 32) | lo;
>>> +}
>>> +#endif /* CONFIG_64BIT */
>>> +static int clint_clock_next_event(unsigned long delta,
>>> + struct clock_event_device *ce)
>>> +{
>>> + void __iomem *r = clint_timer_cmp +
>>> + cpuid_to_hartid_map(smp_processor_id());
>>> +
>>> + csr_set(CSR_IE, IE_TIE);
>>> + writeq_relaxed(clint_get_cycles64() + delta, r);
>>> + return 0;
>>> +}
>>> +
>>> +static DEFINE_PER_CPU(struct clock_event_device, clint_clock_event) = {
>>> + .name = "clint_clockevent",
>>> + .features = CLOCK_EVT_FEAT_ONESHOT,
>>> + .rating = 100,
>>> + .set_next_event = clint_clock_next_event,
>>> +};
>>> +
>>> +static u64 clint_rdtime(struct clocksource *cs)
>>> +{
>>> + return readq_relaxed(clint_timer_val);
>>> +}
>>> +
>>> +static u64 notrace clint_sched_clock(void)
>>> +{
>>> + return readq_relaxed(clint_timer_val);
>>> +}
>>> +
>>> +static struct clocksource clint_clocksource = {
>>> + .name = "clint_clocksource",
>>> + .rating = 300,
>>> + .mask = CLOCKSOURCE_MASK(64),
>>> + .flags = CLOCK_SOURCE_IS_CONTINUOUS,
>>> + .read = clint_rdtime,
>>
>> What if !CONFIG_64BIT
>
> The CLINT counter is 64bit for both 32bit and 64bit systems
> but I should have used clint_get_cycles64() in clint_rdtime().
> I will update it.
>
>>
>>> +};
>>> +
>>> +static int clint_timer_starting_cpu(unsigned int cpu)
>>> +{
>>> + struct clock_event_device *ce = per_cpu_ptr(&clint_clock_event, cpu);
>>> +
>>> + ce->cpumask = cpumask_of(cpu);
>>> + clockevents_config_and_register(ce, clint_timer_freq, 200, ULONG_MAX);
>>
>> The function is not immune against registering the same clockevents. If
>> the CPU is hotplugged several times, this function will be called again
>> and again. Why not rely on a for_each_possible_cpu loop in the init
>> function ?
>>
>>> + enable_percpu_irq(clint_timer_irq,
>>> + irq_get_trigger_type(clint_timer_irq));
>>
>> Why do you want to enable / disable the interrrupts ? The should be
>> already handle by the hotplug framework no ?
>
> The perCPU interrupts are not enabled by default. We have to
> explicitly enable/disable perCPU interrupts in CPU hotplug callbacks.
>

Isn't is possible to do that in the probe/init function ?



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2020-07-17 05:58:20

by Anup Patel

Subject: Re: [PATCH v3 2/4] clocksource/drivers: Add CLINT timer driver

On Fri, Jul 17, 2020 at 10:58 AM Daniel Lezcano
<[email protected]> wrote:
>
> On 17/07/2020 07:21, Anup Patel wrote:
> > On Fri, Jul 17, 2020 at 2:57 AM Daniel Lezcano
> > <[email protected]> wrote:
> >>
> >>
> >> Hi Anup,
> >>
> >>
> >> On 15/07/2020 09:15, Anup Patel wrote:
> >>> The TIME CSR and SBI calls are not available in RISC-V M-mode so we
> >>> separate add CLINT driver for Linux RISC-V M-mode (i.e. RISC-V NoMMU
> >>> kernel).
> >>
> >> The description is confusing, please reword it and give a bit more
> >> information about the timer itself, especially, the IPI thing.
> >
> > Okay, will update.
> >
> >>
> >>> Signed-off-by: Anup Patel <[email protected]>
> >>> ---
> >>> drivers/clocksource/Kconfig | 10 ++
> >>> drivers/clocksource/Makefile | 1 +
> >>> drivers/clocksource/timer-clint.c | 229 ++++++++++++++++++++++++++++++
> >>> include/linux/cpuhotplug.h | 1 +
> >>> 4 files changed, 241 insertions(+)
> >>> create mode 100644 drivers/clocksource/timer-clint.c
> >>>
> >>> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> >>> index 91418381fcd4..eabcf1cfb0c0 100644
> >>> --- a/drivers/clocksource/Kconfig
> >>> +++ b/drivers/clocksource/Kconfig
> >>> @@ -658,6 +658,16 @@ config RISCV_TIMER
> >>> is accessed via both the SBI and the rdcycle instruction. This is
> >>> required for all RISC-V systems.
> >>>
> >>> +config CLINT_TIMER
> >>> + bool "Timer for the RISC-V platform"
> >>> + depends on GENERIC_SCHED_CLOCK && RISCV_M_MODE
> >>> + default y
> >>> + select TIMER_PROBE
> >>> + select TIMER_OF
> >>> + help
> >>> + This option enables the CLINT timer for RISC-V systems. The CLINT
> >>> + driver is usually used for NoMMU RISC-V systems.
> >>
> >> For the timer, we do silent option and let the platform config select
> >> it. Please refer to other timer option below as reference.
> >
> > Okay, I will use "default RISCV" instead of "default y" (just like other
> > timer Kconfig options).
>
> Preferably, select it from the platform's Kconfig.

Okay, I will update.

>
> >>
> >>> config CSKY_MP_TIMER
> >>> bool "SMP Timer for the C-SKY platform" if COMPILE_TEST
> >>> depends on CSKY
> >>> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> >>> index bdda1a2e4097..18e700e703a0 100644
> >>> --- a/drivers/clocksource/Makefile
> >>> +++ b/drivers/clocksource/Makefile
> >>> @@ -87,6 +87,7 @@ obj-$(CONFIG_CLKSRC_ST_LPC) += clksrc_st_lpc.o
> >>> obj-$(CONFIG_X86_NUMACHIP) += numachip.o
> >>> obj-$(CONFIG_ATCPIT100_TIMER) += timer-atcpit100.o
> >>> obj-$(CONFIG_RISCV_TIMER) += timer-riscv.o
> >>> +obj-$(CONFIG_CLINT_TIMER) += timer-clint.o
> >>> obj-$(CONFIG_CSKY_MP_TIMER) += timer-mp-csky.o
> >>> obj-$(CONFIG_GX6605S_TIMER) += timer-gx6605s.o
> >>> obj-$(CONFIG_HYPERV_TIMER) += hyperv_timer.o
> >>> diff --git a/drivers/clocksource/timer-clint.c b/drivers/clocksource/timer-clint.c
> >>> new file mode 100644
> >>> index 000000000000..bfc38bb5a589
> >>> --- /dev/null
> >>> +++ b/drivers/clocksource/timer-clint.c
> >>> @@ -0,0 +1,229 @@
> >>> +// SPDX-License-Identifier: GPL-2.0
> >>> +/*
> >>> + * Copyright (C) 2020 Western Digital Corporation or its affiliates.
> >>> + *
> >>> + * Most of the M-mode (i.e. NoMMU) RISC-V systems usually have a
> >>> + * CLINT MMIO timer device.
> >>> + */
> >>> +
> >>> +#define pr_fmt(fmt) "clint: " fmt
> >>> +#include <linux/bitops.h>
> >>> +#include <linux/clocksource.h>
> >>> +#include <linux/clockchips.h>
> >>> +#include <linux/cpu.h>
> >>> +#include <linux/delay.h>
> >>> +#include <linux/module.h>
> >>> +#include <linux/of_address.h>
> >>> +#include <linux/sched_clock.h>
> >>> +#include <linux/io-64-nonatomic-lo-hi.h>
> >>> +#include <linux/interrupt.h>
> >>> +#include <linux/of_irq.h>
> >>> +#include <linux/smp.h>
> >>> +
> >>> +#define CLINT_IPI_OFF 0
> >>> +#define CLINT_TIMER_CMP_OFF 0x4000
> >>> +#define CLINT_TIMER_VAL_OFF 0xbff8
> >>> +
> >>> +/* CLINT manages IPI and Timer for RISC-V M-mode */
> >>> +static u32 __iomem *clint_ipi_base;
> >>> +static u64 __iomem *clint_timer_cmp;
> >>> +static u64 __iomem *clint_timer_val;
> >>> +static unsigned long clint_timer_freq;
> >>> +static unsigned int clint_timer_irq;
> >>> +
> >>> +static void clint_send_ipi(const struct cpumask *target)
> >>> +{
> >>> + unsigned int cpu;
> >>> +
> >>> + for_each_cpu(cpu, target)
> >>> + writel(1, clint_ipi_base + cpuid_to_hartid_map(cpu));
> >>> +}
> >>> +
> >>> +static void clint_clear_ipi(void)
> >>> +{
> >>> + writel(0, clint_ipi_base + cpuid_to_hartid_map(smp_processor_id()));
> >>> +}
> >>> +
> >>> +static struct riscv_ipi_ops clint_ipi_ops = {
> >>> + .ipi_inject = clint_send_ipi,
> >>> + .ipi_clear = clint_clear_ipi,
> >>> +};
> >>> +
> >>> +#ifdef CONFIG_64BIT
> >>> +#define clint_get_cycles() readq_relaxed(clint_timer_val)
> >>> +#else
> >>> +#define clint_get_cycles() readl_relaxed(clint_timer_val)
> >>> +#define clint_get_cycles_hi() readl_relaxed(((u32 *)clint_timer_val) + 1)
> >>> +#endif
> >>> +
> >>> +#ifdef CONFIG_64BIT
> >>> +static u64 clint_get_cycles64(void)
> >>> +{
> >>> + return clint_get_cycles();
> >>> +}
> >>> +#else /* CONFIG_64BIT */
> >>> +static u64 clint_get_cycles64(void)
> >>> +{
> >>> + u32 hi, lo;
> >>> +
> >>> + do {
> >>> + hi = clint_get_cycles_hi();
> >>> + lo = clint_get_cycles();
> >>> + } while (hi != clint_get_cycles_hi());
> >>> +
> >>> + return ((u64)hi << 32) | lo;
> >>> +}
> >>> +#endif /* CONFIG_64BIT */
> >>> +static int clint_clock_next_event(unsigned long delta,
> >>> + struct clock_event_device *ce)
> >>> +{
> >>> + void __iomem *r = clint_timer_cmp +
> >>> + cpuid_to_hartid_map(smp_processor_id());
> >>> +
> >>> + csr_set(CSR_IE, IE_TIE);
> >>> + writeq_relaxed(clint_get_cycles64() + delta, r);
> >>> + return 0;
> >>> +}
> >>> +
> >>> +static DEFINE_PER_CPU(struct clock_event_device, clint_clock_event) = {
> >>> + .name = "clint_clockevent",
> >>> + .features = CLOCK_EVT_FEAT_ONESHOT,
> >>> + .rating = 100,
> >>> + .set_next_event = clint_clock_next_event,
> >>> +};
> >>> +
> >>> +static u64 clint_rdtime(struct clocksource *cs)
> >>> +{
> >>> + return readq_relaxed(clint_timer_val);
> >>> +}
> >>> +
> >>> +static u64 notrace clint_sched_clock(void)
> >>> +{
> >>> + return readq_relaxed(clint_timer_val);
> >>> +}
> >>> +
> >>> +static struct clocksource clint_clocksource = {
> >>> + .name = "clint_clocksource",
> >>> + .rating = 300,
> >>> + .mask = CLOCKSOURCE_MASK(64),
> >>> + .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> >>> + .read = clint_rdtime,
> >>
> >> What if !CONFIG_64BIT
> >
> > The CLINT counter is 64bit for both 32bit and 64bit systems
> > but I should have used clint_get_cycles64() in clint_rdtime().
> > I will update it.
> >
> >>
> >>> +};
> >>> +
> >>> +static int clint_timer_starting_cpu(unsigned int cpu)
> >>> +{
> >>> + struct clock_event_device *ce = per_cpu_ptr(&clint_clock_event, cpu);
> >>> +
> >>> + ce->cpumask = cpumask_of(cpu);
> >>> + clockevents_config_and_register(ce, clint_timer_freq, 200, ULONG_MAX);
> >>
> >> The function is not immune against registering the same clockevents. If
> >> the CPU is hotplugged several times, this function will be called again
> >> and again. Why not rely on a for_each_possible_cpu loop in the init
> >> function ?
> >>
> >>> + enable_percpu_irq(clint_timer_irq,
> >>> + irq_get_trigger_type(clint_timer_irq));
> >>
> >> Why do you want to enable / disable the interrrupts ? The should be
> >> already handle by the hotplug framework no ?
> >
> > The perCPU interrupts are not enabled by default. We have to
> > explicitly enable/disable perCPU interrupts in CPU hotplug callbacks.
> >
>
> Isn't is possible to do that in the probe/init function ?

The enable_percpu_irq() and disable_percpu_irq() work for current
CPU only. This means we have to call these functions separately on
each CPU.

>
>
>
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>
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