From: Sudeep KarkadaNagesha <[email protected]>
This patch series adds support to configure the rate and enable the
event stream for architected timer. The event streams can be used to
impose a timeout on a wfe, to safeguard against any programming error
in case an expected event is not generated or even to implement
wfe-based timeouts for userspace locking implementations. This feature
can be disabled(enabled by default).
Since the timer control register is reset to zero on warm boot, CPU
PM notifier is added to save and restore the value.
Changes v5->v6:
1. Disabling event stream by default on boot and enable it
only if CONFIG_ARM_ARCH_TIMER_EVTSTREAM=y
This removes runtime configuration of timer event stream.
2. Moved COMPAT_ELF_HWCAP_DEFAULT to arch/arm64/kernel/setup.c
Changes v4->v5:
1. Removed compat_dyn_elf_hwcap and used just compat_elf_hwcap as per
Catalin's suggestion
2. Instead of resetting event stream in CPU PM callbacks, saving and
restoring counter control register now.
Changes v3->v4:
1. Added a config option to en/disable the timer event stream feature.
Due to this the ordering of the patches as well as some cosmetic
code changes are done.( So dropped previous reviewed-by tags)
2. Removed exporting compat_dyn_elf_hwcap as there are no modules
requiring it for now.
Changes v2->v3:
1. Moved ARM and ARM64 changes into separate patches
2. Added native hwcaps definations(ARM/ARM64) and compat-specific
definitions(ARM64) to the users for the event stream feature.
Changes v1->v2:
1. Saved event stream divider value on cold reset path and re-used it
in CPU PM notifier instead of calculating every time.
2. Rebased on v3.11-rc2(to avoid conflicts with __cpuinit* deletion)
3. Dropped "ARM/ARM64: arch_timer: remove __cpuinit attribute for
arch_counter_set_user_access"(already done as part of __cpuinit*
deletion)
Regards,
Sudeep
Sudeep KarkadaNagesha (4):
ARM/ARM64: arch_timer: add macros for bits in control register
ARM: arch_timer: add support to configure and enable event stream
ARM64: arch_timer: add support to configure and enable event stream
drivers: clocksource: add CPU PM notifier for ARM architected timer
Will Deacon (1):
drivers: clocksource: add support for ARM architected timer event
stream
arch/arm/include/asm/arch_timer.h | 36 ++++++++++++++++++++++----
arch/arm/include/uapi/asm/hwcap.h | 1 +
arch/arm/kernel/setup.c | 1 +
arch/arm64/include/asm/arch_timer.h | 42 ++++++++++++++++++++++++++-----
arch/arm64/include/asm/hwcap.h | 11 ++++----
arch/arm64/include/uapi/asm/hwcap.h | 1 +
arch/arm64/kernel/setup.c | 11 ++++++++
drivers/clocksource/Kconfig | 14 +++++++++++
drivers/clocksource/arm_arch_timer.c | 49 ++++++++++++++++++++++++++++++++++++
include/clocksource/arm_arch_timer.h | 10 ++++++++
10 files changed, 160 insertions(+), 16 deletions(-)
--
1.8.1.2
From: Sudeep KarkadaNagesha <[email protected]>
This patch adds support for configuring the event stream frequency
and enabling it.
It also adds the hwcaps definitions to the user to detect this event
stream feature.
Cc: Russell King <[email protected]>
Cc: Lorenzo Pieralisi <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Catalin Marinas <[email protected]>
Signed-off-by: Sudeep KarkadaNagesha <[email protected]>
---
arch/arm/include/asm/arch_timer.h | 27 ++++++++++++++++++++++++---
arch/arm/include/uapi/asm/hwcap.h | 1 +
arch/arm/kernel/setup.c | 1 +
3 files changed, 26 insertions(+), 3 deletions(-)
diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
index 1a3e967..f10cd1c 100644
--- a/arch/arm/include/asm/arch_timer.h
+++ b/arch/arm/include/asm/arch_timer.h
@@ -89,11 +89,21 @@ static inline u64 arch_counter_get_cntvct(void)
return cval;
}
-static inline void arch_counter_set_user_access(void)
+static inline u32 arch_timer_get_cntkctl(void)
{
u32 cntkctl;
-
asm volatile("mrc p15, 0, %0, c14, c1, 0" : "=r" (cntkctl));
+ return cntkctl;
+}
+
+static inline void arch_timer_set_cntkctl(u32 cntkctl)
+{
+ asm volatile("mcr p15, 0, %0, c14, c1, 0" : : "r" (cntkctl));
+}
+
+static inline void arch_counter_set_user_access(void)
+{
+ u32 cntkctl = arch_timer_get_cntkctl();
/* Disable user access to both physical/virtual counters/timers */
/* Also disable virtual event stream */
@@ -102,9 +112,20 @@ static inline void arch_counter_set_user_access(void)
| ARCH_TIMER_VIRT_EVT_EN
| ARCH_TIMER_USR_VCT_ACCESS_EN
| ARCH_TIMER_USR_PCT_ACCESS_EN);
+ arch_timer_set_cntkctl(cntkctl);
+}
- asm volatile("mcr p15, 0, %0, c14, c1, 0" : : "r" (cntkctl));
+static inline void arch_timer_evtstrm_enable(int divider)
+{
+ u32 cntkctl = arch_timer_get_cntkctl();
+ cntkctl &= ~ARCH_TIMER_EVT_TRIGGER_MASK;
+ /* Set the divider and enable virtual event stream */
+ cntkctl |= (divider << ARCH_TIMER_EVT_TRIGGER_SHIFT)
+ | ARCH_TIMER_VIRT_EVT_EN;
+ arch_timer_set_cntkctl(cntkctl);
+ elf_hwcap |= HWCAP_EVTSTRM;
}
+
#endif
#endif
diff --git a/arch/arm/include/uapi/asm/hwcap.h b/arch/arm/include/uapi/asm/hwcap.h
index 6d34d08..7dcc10d 100644
--- a/arch/arm/include/uapi/asm/hwcap.h
+++ b/arch/arm/include/uapi/asm/hwcap.h
@@ -26,5 +26,6 @@
#define HWCAP_VFPD32 (1 << 19) /* set if VFP has 32 regs (not 16) */
#define HWCAP_IDIV (HWCAP_IDIVA | HWCAP_IDIVT)
#define HWCAP_LPAE (1 << 20)
+#define HWCAP_EVTSTRM (1 << 21)
#endif /* _UAPI__ASMARM_HWCAP_H */
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index afc2489..305ffc9 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -975,6 +975,7 @@ static const char *hwcap_str[] = {
"idivt",
"vfpd32",
"lpae",
+ "evtstrm",
NULL
};
--
1.8.1.2
From: Sudeep KarkadaNagesha <[email protected]>
Few control settings done in architected timer as part of initialisation
can be lost when CPU enters deeper power states. They need to be
restored when the CPU is (warm)reset again.
This patch adds CPU PM notifiers to save the counter control register
when entering low power modes and restore it when CPU exits low power.
Cc: Catalin Marinas <[email protected]>
Reviewed-by: Lorenzo Pieralisi <[email protected]>
Reviewed-by: Will Deacon <[email protected]>
Signed-off-by: Sudeep KarkadaNagesha <[email protected]>
---
drivers/clocksource/arm_arch_timer.c | 34 ++++++++++++++++++++++++++++++++++
1 file changed, 34 insertions(+)
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 9777b36..611f9cb 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -13,6 +13,7 @@
#include <linux/device.h>
#include <linux/smp.h>
#include <linux/cpu.h>
+#include <linux/cpu_pm.h>
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/of_irq.h>
@@ -275,6 +276,33 @@ static struct notifier_block arch_timer_cpu_nb = {
.notifier_call = arch_timer_cpu_notify,
};
+#ifdef CONFIG_CPU_PM
+static unsigned int saved_cntkctl;
+static int arch_timer_cpu_pm_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu)
+{
+ if (action == CPU_PM_ENTER)
+ saved_cntkctl = arch_timer_get_cntkctl();
+ else if (action == CPU_PM_ENTER_FAILED || action == CPU_PM_EXIT)
+ arch_timer_set_cntkctl(saved_cntkctl);
+ return NOTIFY_OK;
+}
+
+static struct notifier_block arch_timer_cpu_pm_notifier = {
+ .notifier_call = arch_timer_cpu_pm_notify,
+};
+
+static int __init arch_timer_cpu_pm_init(void)
+{
+ return cpu_pm_register_notifier(&arch_timer_cpu_pm_notifier);
+}
+#else
+static int __init arch_timer_cpu_pm_init(void)
+{
+ return 0;
+}
+#endif
+
static int __init arch_timer_register(void)
{
int err;
@@ -324,11 +352,17 @@ static int __init arch_timer_register(void)
if (err)
goto out_free_irq;
+ err = arch_timer_cpu_pm_init();
+ if (err)
+ goto out_unreg_notify;
+
/* Immediately configure the timer on the boot CPU */
arch_timer_setup(this_cpu_ptr(arch_timer_evt));
return 0;
+out_unreg_notify:
+ unregister_cpu_notifier(&arch_timer_cpu_nb);
out_free_irq:
if (arch_timer_use_virtual)
free_percpu_irq(arch_timer_ppi[VIRT_PPI], arch_timer_evt);
--
1.8.1.2
From: Sudeep KarkadaNagesha <[email protected]>
Add macros to describe the bitfields in the ARM architected timer
control register to make code easy to understand.
Cc: Catalin Marinas <[email protected]>
Reviewed-by: Lorenzo Pieralisi <[email protected]>
Reviewed-by: Will Deacon <[email protected]>
Signed-off-by: Sudeep KarkadaNagesha <[email protected]>
---
arch/arm/include/asm/arch_timer.h | 9 +++++++--
arch/arm64/include/asm/arch_timer.h | 12 ++++++++----
include/clocksource/arm_arch_timer.h | 8 ++++++++
3 files changed, 23 insertions(+), 6 deletions(-)
diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
index e406d57..1a3e967 100644
--- a/arch/arm/include/asm/arch_timer.h
+++ b/arch/arm/include/asm/arch_timer.h
@@ -95,8 +95,13 @@ static inline void arch_counter_set_user_access(void)
asm volatile("mrc p15, 0, %0, c14, c1, 0" : "=r" (cntkctl));
- /* disable user access to everything */
- cntkctl &= ~((3 << 8) | (7 << 0));
+ /* Disable user access to both physical/virtual counters/timers */
+ /* Also disable virtual event stream */
+ cntkctl &= ~(ARCH_TIMER_USR_PT_ACCESS_EN
+ | ARCH_TIMER_USR_VT_ACCESS_EN
+ | ARCH_TIMER_VIRT_EVT_EN
+ | ARCH_TIMER_USR_VCT_ACCESS_EN
+ | ARCH_TIMER_USR_PCT_ACCESS_EN);
asm volatile("mcr p15, 0, %0, c14, c1, 0" : : "r" (cntkctl));
}
diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
index 98abd47..fa4af76 100644
--- a/arch/arm64/include/asm/arch_timer.h
+++ b/arch/arm64/include/asm/arch_timer.h
@@ -101,12 +101,16 @@ static inline void arch_counter_set_user_access(void)
{
u32 cntkctl;
- /* Disable user access to the timers and the physical counter. */
asm volatile("mrs %0, cntkctl_el1" : "=r" (cntkctl));
- cntkctl &= ~((3 << 8) | (1 << 0));
- /* Enable user access to the virtual counter and frequency. */
- cntkctl |= (1 << 1);
+ /* Disable user access to the timers and the physical counter */
+ cntkctl &= ~(ARCH_TIMER_USR_PT_ACCESS_EN
+ | ARCH_TIMER_USR_VT_ACCESS_EN
+ | ARCH_TIMER_USR_PCT_ACCESS_EN);
+
+ /* Enable user access to the virtual counter */
+ cntkctl |= ARCH_TIMER_USR_VCT_ACCESS_EN;
+
asm volatile("msr cntkctl_el1, %0" : : "r" (cntkctl));
}
diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
index c463ce9..551f7e9 100644
--- a/include/clocksource/arm_arch_timer.h
+++ b/include/clocksource/arm_arch_timer.h
@@ -29,6 +29,14 @@
#define ARCH_TIMER_PHYS_ACCESS 0
#define ARCH_TIMER_VIRT_ACCESS 1
+#define ARCH_TIMER_USR_PCT_ACCESS_EN (1 << 0) /* physical counter */
+#define ARCH_TIMER_USR_VCT_ACCESS_EN (1 << 1) /* virtual counter */
+#define ARCH_TIMER_VIRT_EVT_EN (1 << 2)
+#define ARCH_TIMER_EVT_TRIGGER_SHIFT (4)
+#define ARCH_TIMER_EVT_TRIGGER_MASK (0xF << ARCH_TIMER_EVT_TRIGGER_SHIFT)
+#define ARCH_TIMER_USR_VT_ACCESS_EN (1 << 8) /* virtual timer registers */
+#define ARCH_TIMER_USR_PT_ACCESS_EN (1 << 9) /* physical timer registers */
+
#ifdef CONFIG_ARM_ARCH_TIMER
extern u32 arch_timer_get_rate(void);
--
1.8.1.2
From: Will Deacon <[email protected]>
The ARM architected timer can generate events (used for waking up
CPUs executing the wfe instruction) at a frequency represented as a
power-of-2 divisor of the clock rate.
An event stream might be used:
- To impose a time-out on a wfe polling loop.
- To safeguard against any programming error in case an expected event
is not generated.
- To implement wfe-based timeouts for userspace locking implementations.
This patch computes the event stream frequency aiming for a period
of 100us between events. It uses ARM/ARM64 specific backends to configure
and enable the event stream.
Cc: Lorenzo Pieralisi <[email protected]>
Cc: Catalin Marinas <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
[sudeep: moving ARM/ARM64 changes into separate patches
and adding Kconfig option]
Signed-off-by: Sudeep KarkadaNagesha <[email protected]>
---
drivers/clocksource/Kconfig | 14 ++++++++++++++
drivers/clocksource/arm_arch_timer.c | 15 +++++++++++++++
include/clocksource/arm_arch_timer.h | 2 ++
3 files changed, 31 insertions(+)
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index b7b9b04..49f1f6e 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -74,6 +74,20 @@ config ARM_ARCH_TIMER
bool
select CLKSRC_OF if OF
+config ARM_ARCH_TIMER_EVTSTREAM
+ bool "Support for ARM architected timer event stream generation"
+ default y if ARM_ARCH_TIMER
+ help
+ This option enables support for event stream generation based on
+ the ARM architected timer. It is used for waking up CPUs executing
+ the wfe instruction at a frequency represented as a power-of-2
+ divisor of the clock rate. An event stream might be mainly useful
+ for wfe-based timeouts for userspace locking implementations.
+ It might also be useful for imposing timeout on a wfe or even
+ safeguarding against any programming errors in case an expected
+ event is not generated. This must be disabled for hardware validation
+ purposes to detect any hardware anomalies of missing events.
+
config ARM_GLOBAL_TIMER
bool
select CLKSRC_OF if OF
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index ffadd83..9777b36 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -123,6 +123,19 @@ static int arch_timer_set_next_event_phys(unsigned long evt,
return 0;
}
+static void arch_timer_enable_evtstream(void)
+{
+ int evt_stream_div, pos;
+
+ /* Find the closest power of two to the divisor */
+ evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ;
+ pos = fls(evt_stream_div);
+ if (pos > 1 && !(evt_stream_div & (1 << (pos - 2))))
+ pos--;
+ /* enable event stream */
+ arch_timer_evtstrm_enable(min(pos, 15));
+}
+
static int arch_timer_setup(struct clock_event_device *clk)
{
clk->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP;
@@ -154,6 +167,8 @@ static int arch_timer_setup(struct clock_event_device *clk)
}
arch_counter_set_user_access();
+ if (IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM))
+ arch_timer_enable_evtstream();
return 0;
}
diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
index 551f7e9..c4d0fc4 100644
--- a/include/clocksource/arm_arch_timer.h
+++ b/include/clocksource/arm_arch_timer.h
@@ -37,6 +37,8 @@
#define ARCH_TIMER_USR_VT_ACCESS_EN (1 << 8) /* virtual timer registers */
#define ARCH_TIMER_USR_PT_ACCESS_EN (1 << 9) /* physical timer registers */
+#define ARCH_TIMER_EVT_STREAM_FREQ 10000 /* 100us */
+
#ifdef CONFIG_ARM_ARCH_TIMER
extern u32 arch_timer_get_rate(void);
--
1.8.1.2
From: Sudeep KarkadaNagesha <[email protected]>
This patch adds support for configuring the event stream frequency
and enabling it.
It also adds the hwcaps as well as compat-specific definitions to
the user to detect this event stream feature.
Cc: Lorenzo Pieralisi <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Catalin Marinas <[email protected]>
Signed-off-by: Sudeep KarkadaNagesha <[email protected]>
---
arch/arm64/include/asm/arch_timer.h | 32 +++++++++++++++++++++++++++++---
arch/arm64/include/asm/hwcap.h | 11 ++++++-----
arch/arm64/include/uapi/asm/hwcap.h | 1 +
arch/arm64/kernel/setup.c | 11 +++++++++++
4 files changed, 47 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
index fa4af76..3bca364 100644
--- a/arch/arm64/include/asm/arch_timer.h
+++ b/arch/arm64/include/asm/arch_timer.h
@@ -97,21 +97,47 @@ static inline u32 arch_timer_get_cntfrq(void)
return val;
}
-static inline void arch_counter_set_user_access(void)
+static inline u32 arch_timer_get_cntkctl(void)
{
u32 cntkctl;
-
asm volatile("mrs %0, cntkctl_el1" : "=r" (cntkctl));
+ return cntkctl;
+}
+
+static inline void arch_timer_set_cntkctl(u32 cntkctl)
+{
+ asm volatile("msr cntkctl_el1, %0" : : "r" (cntkctl));
+}
+
+static inline void arch_counter_set_user_access(void)
+{
+ u32 cntkctl = arch_timer_get_cntkctl();
/* Disable user access to the timers and the physical counter */
+ /* Also disable virtual event stream */
cntkctl &= ~(ARCH_TIMER_USR_PT_ACCESS_EN
| ARCH_TIMER_USR_VT_ACCESS_EN
+ | ARCH_TIMER_VIRT_EVT_EN
| ARCH_TIMER_USR_PCT_ACCESS_EN);
/* Enable user access to the virtual counter */
cntkctl |= ARCH_TIMER_USR_VCT_ACCESS_EN;
- asm volatile("msr cntkctl_el1, %0" : : "r" (cntkctl));
+ arch_timer_set_cntkctl(cntkctl);
+}
+
+static inline void arch_timer_evtstrm_enable(int divider)
+{
+ u32 cntkctl = arch_timer_get_cntkctl();
+ cntkctl &= ~ARCH_TIMER_EVT_TRIGGER_MASK;
+ /* Set the divider and enable virtual event stream */
+ cntkctl |= (divider << ARCH_TIMER_EVT_TRIGGER_SHIFT)
+ | ARCH_TIMER_VIRT_EVT_EN;
+ arch_timer_set_cntkctl(cntkctl);
+ elf_hwcap |= HWCAP_EVTSTRM;
+#ifdef CONFIG_COMPAT
+ compat_elf_hwcap |= COMPAT_HWCAP_EVTSTRM;
+#endif
}
static inline u64 arch_counter_get_cntvct(void)
diff --git a/arch/arm64/include/asm/hwcap.h b/arch/arm64/include/asm/hwcap.h
index 6d4482f..3a48433 100644
--- a/arch/arm64/include/asm/hwcap.h
+++ b/arch/arm64/include/asm/hwcap.h
@@ -30,6 +30,7 @@
#define COMPAT_HWCAP_IDIVA (1 << 17)
#define COMPAT_HWCAP_IDIVT (1 << 18)
#define COMPAT_HWCAP_IDIV (COMPAT_HWCAP_IDIVA|COMPAT_HWCAP_IDIVT)
+#define COMPAT_HWCAP_EVTSTRM (1 << 21)
#ifndef __ASSEMBLY__
/*
@@ -37,11 +38,11 @@
* instruction set this cpu supports.
*/
#define ELF_HWCAP (elf_hwcap)
-#define COMPAT_ELF_HWCAP (COMPAT_HWCAP_HALF|COMPAT_HWCAP_THUMB|\
- COMPAT_HWCAP_FAST_MULT|COMPAT_HWCAP_EDSP|\
- COMPAT_HWCAP_TLS|COMPAT_HWCAP_VFP|\
- COMPAT_HWCAP_VFPv3|COMPAT_HWCAP_VFPv4|\
- COMPAT_HWCAP_NEON|COMPAT_HWCAP_IDIV)
+
+#ifdef CONFIG_COMPAT
+#define COMPAT_ELF_HWCAP (compat_elf_hwcap)
+extern unsigned int compat_elf_hwcap;
+#endif
extern unsigned int elf_hwcap;
#endif
diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h
index eea4975..9b12476 100644
--- a/arch/arm64/include/uapi/asm/hwcap.h
+++ b/arch/arm64/include/uapi/asm/hwcap.h
@@ -21,6 +21,7 @@
*/
#define HWCAP_FP (1 << 0)
#define HWCAP_ASIMD (1 << 1)
+#define HWCAP_EVTSTRM (1 << 2)
#endif /* _UAPI__ASM_HWCAP_H */
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index add6ea6..57cb006 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -60,6 +60,16 @@ EXPORT_SYMBOL(processor_id);
unsigned int elf_hwcap __read_mostly;
EXPORT_SYMBOL_GPL(elf_hwcap);
+#ifdef CONFIG_COMPAT
+#define COMPAT_ELF_HWCAP_DEFAULT \
+ (COMPAT_HWCAP_HALF|COMPAT_HWCAP_THUMB|\
+ COMPAT_HWCAP_FAST_MULT|COMPAT_HWCAP_EDSP|\
+ COMPAT_HWCAP_TLS|COMPAT_HWCAP_VFP|\
+ COMPAT_HWCAP_VFPv3|COMPAT_HWCAP_VFPv4|\
+ COMPAT_HWCAP_NEON|COMPAT_HWCAP_IDIV)
+unsigned int compat_elf_hwcap __read_mostly = COMPAT_ELF_HWCAP_DEFAULT;
+#endif
+
static const char *cpu_name;
static const char *machine_name;
phys_addr_t __fdt_pointer __initdata;
@@ -309,6 +319,7 @@ subsys_initcall(topology_init);
static const char *hwcap_str[] = {
"fp",
"asimd",
+ "evtstrm",
NULL
};
--
1.8.1.2
On Thu, Aug 29, 2013 at 03:55:41PM +0100, Sudeep KarkadaNagesha wrote:
> From: Will Deacon <[email protected]>
>
> The ARM architected timer can generate events (used for waking up
> CPUs executing the wfe instruction) at a frequency represented as a
> power-of-2 divisor of the clock rate.
>
> An event stream might be used:
> - To impose a time-out on a wfe polling loop.
> - To safeguard against any programming error in case an expected event
> is not generated.
> - To implement wfe-based timeouts for userspace locking implementations.
>
> This patch computes the event stream frequency aiming for a period
> of 100us between events. It uses ARM/ARM64 specific backends to configure
> and enable the event stream.
>
> Cc: Lorenzo Pieralisi <[email protected]>
> Cc: Catalin Marinas <[email protected]>
> Signed-off-by: Will Deacon <[email protected]>
> [sudeep: moving ARM/ARM64 changes into separate patches
> and adding Kconfig option]
> Signed-off-by: Sudeep KarkadaNagesha <[email protected]>
> ---
> drivers/clocksource/Kconfig | 14 ++++++++++++++
> drivers/clocksource/arm_arch_timer.c | 15 +++++++++++++++
> include/clocksource/arm_arch_timer.h | 2 ++
> 3 files changed, 31 insertions(+)
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index b7b9b04..49f1f6e 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -74,6 +74,20 @@ config ARM_ARCH_TIMER
> bool
> select CLKSRC_OF if OF
>
> +config ARM_ARCH_TIMER_EVTSTREAM
> + bool "Support for ARM architected timer event stream generation"
> + default y if ARM_ARCH_TIMER
> + help
> + This option enables support for event stream generation based on
> + the ARM architected timer. It is used for waking up CPUs executing
> + the wfe instruction at a frequency represented as a power-of-2
> + divisor of the clock rate. An event stream might be mainly useful
> + for wfe-based timeouts for userspace locking implementations.
I would be a bit more assertive here, something like "the main use of
the event stream is wfe-based timeouts of userspace locking
implementations."
> + It might also be useful for imposing timeout on a wfe or even
> + safeguarding against any programming errors in case an expected
Maybe "imposting timeout on wfe to safeguard against ...". We already
mentioned wfe-based timeout above.
Otherwise, for the whole series:
Reviewed-by: Catalin Marinas <[email protected]>
On 29/08/13 16:39, Catalin Marinas wrote:
> On Thu, Aug 29, 2013 at 03:55:41PM +0100, Sudeep KarkadaNagesha wrote:
>> From: Will Deacon <[email protected]>
>>
>> The ARM architected timer can generate events (used for waking up
>> CPUs executing the wfe instruction) at a frequency represented as a
>> power-of-2 divisor of the clock rate.
>>
>> An event stream might be used:
>> - To impose a time-out on a wfe polling loop.
>> - To safeguard against any programming error in case an expected event
>> is not generated.
>> - To implement wfe-based timeouts for userspace locking implementations.
>>
>> This patch computes the event stream frequency aiming for a period
>> of 100us between events. It uses ARM/ARM64 specific backends to configure
>> and enable the event stream.
>>
>> Cc: Lorenzo Pieralisi <[email protected]>
>> Cc: Catalin Marinas <[email protected]>
>> Signed-off-by: Will Deacon <[email protected]>
>> [sudeep: moving ARM/ARM64 changes into separate patches
>> and adding Kconfig option]
>> Signed-off-by: Sudeep KarkadaNagesha <[email protected]>
>> ---
>> drivers/clocksource/Kconfig | 14 ++++++++++++++
>> drivers/clocksource/arm_arch_timer.c | 15 +++++++++++++++
>> include/clocksource/arm_arch_timer.h | 2 ++
>> 3 files changed, 31 insertions(+)
>>
>> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
>> index b7b9b04..49f1f6e 100644
>> --- a/drivers/clocksource/Kconfig
>> +++ b/drivers/clocksource/Kconfig
>> @@ -74,6 +74,20 @@ config ARM_ARCH_TIMER
>> bool
>> select CLKSRC_OF if OF
>>
>> +config ARM_ARCH_TIMER_EVTSTREAM
>> + bool "Support for ARM architected timer event stream generation"
>> + default y if ARM_ARCH_TIMER
>> + help
>> + This option enables support for event stream generation based on
>> + the ARM architected timer. It is used for waking up CPUs executing
>> + the wfe instruction at a frequency represented as a power-of-2
>> + divisor of the clock rate. An event stream might be mainly useful
>> + for wfe-based timeouts for userspace locking implementations.
>
> I would be a bit more assertive here, something like "the main use of
> the event stream is wfe-based timeouts of userspace locking
> implementations."
>
>> + It might also be useful for imposing timeout on a wfe or even
>> + safeguarding against any programming errors in case an expected
>
> Maybe "imposting timeout on wfe to safeguard against ...". We already
> mentioned wfe-based timeout above.
>
Ok will fix this Kconfig description.
> Otherwise, for the whole series:
>
> Reviewed-by: Catalin Marinas <[email protected]>
>
Thanks.
Regards,
Sudeep
On 29/08/13 15:55, Sudeep KarkadaNagesha wrote:
> From: Sudeep KarkadaNagesha <[email protected]>
>
> This patch series adds support to configure the rate and enable the
> event stream for architected timer. The event streams can be used to
> impose a timeout on a wfe, to safeguard against any programming error
> in case an expected event is not generated or even to implement
> wfe-based timeouts for userspace locking implementations. This feature
> can be disabled(enabled by default).
>
> Since the timer control register is reset to zero on warm boot, CPU
> PM notifier is added to save and restore the value.
>
Hi Russell,
Can you have a look at this series ?
If you are OK, can I have your ACK on arm specific changes(PATCH 2/5) ?
Regards,
Sudeep
> Changes v5->v6:
> 1. Disabling event stream by default on boot and enable it
> only if CONFIG_ARM_ARCH_TIMER_EVTSTREAM=y
> This removes runtime configuration of timer event stream.
> 2. Moved COMPAT_ELF_HWCAP_DEFAULT to arch/arm64/kernel/setup.c
>
> Changes v4->v5:
> 1. Removed compat_dyn_elf_hwcap and used just compat_elf_hwcap as per
> Catalin's suggestion
> 2. Instead of resetting event stream in CPU PM callbacks, saving and
> restoring counter control register now.
>
> Changes v3->v4:
> 1. Added a config option to en/disable the timer event stream feature.
> Due to this the ordering of the patches as well as some cosmetic
> code changes are done.( So dropped previous reviewed-by tags)
> 2. Removed exporting compat_dyn_elf_hwcap as there are no modules
> requiring it for now.
>
> Changes v2->v3:
> 1. Moved ARM and ARM64 changes into separate patches
> 2. Added native hwcaps definations(ARM/ARM64) and compat-specific
> definitions(ARM64) to the users for the event stream feature.
>
> Changes v1->v2:
> 1. Saved event stream divider value on cold reset path and re-used it
> in CPU PM notifier instead of calculating every time.
> 2. Rebased on v3.11-rc2(to avoid conflicts with __cpuinit* deletion)
> 3. Dropped "ARM/ARM64: arch_timer: remove __cpuinit attribute for
> arch_counter_set_user_access"(already done as part of __cpuinit*
> deletion)
>
> Regards,
> Sudeep
>
>
> Sudeep KarkadaNagesha (4):
> ARM/ARM64: arch_timer: add macros for bits in control register
> ARM: arch_timer: add support to configure and enable event stream
> ARM64: arch_timer: add support to configure and enable event stream
> drivers: clocksource: add CPU PM notifier for ARM architected timer
>
> Will Deacon (1):
> drivers: clocksource: add support for ARM architected timer event
> stream
>
> arch/arm/include/asm/arch_timer.h | 36 ++++++++++++++++++++++----
> arch/arm/include/uapi/asm/hwcap.h | 1 +
> arch/arm/kernel/setup.c | 1 +
> arch/arm64/include/asm/arch_timer.h | 42 ++++++++++++++++++++++++++-----
> arch/arm64/include/asm/hwcap.h | 11 ++++----
> arch/arm64/include/uapi/asm/hwcap.h | 1 +
> arch/arm64/kernel/setup.c | 11 ++++++++
> drivers/clocksource/Kconfig | 14 +++++++++++
> drivers/clocksource/arm_arch_timer.c | 49 ++++++++++++++++++++++++++++++++++++
> include/clocksource/arm_arch_timer.h | 10 ++++++++
> 10 files changed, 160 insertions(+), 16 deletions(-)
>
On Fri, Aug 30, 2013 at 11:07:28AM +0100, Sudeep KarkadaNagesha wrote:
> On 29/08/13 15:55, Sudeep KarkadaNagesha wrote:
> > From: Sudeep KarkadaNagesha <[email protected]>
> >
> > This patch series adds support to configure the rate and enable the
> > event stream for architected timer. The event streams can be used to
> > impose a timeout on a wfe, to safeguard against any programming error
> > in case an expected event is not generated or even to implement
> > wfe-based timeouts for userspace locking implementations. This feature
> > can be disabled(enabled by default).
> >
> > Since the timer control register is reset to zero on warm boot, CPU
> > PM notifier is added to save and restore the value.
> >
> Hi Russell,
>
> Can you have a look at this series ?
> If you are OK, can I have your ACK on arm specific changes(PATCH 2/5) ?
I think it would be more value to have someone from ARM Ltd ack it,
because they will know the code much better than I do.
On Fri, Aug 30, 2013 at 12:43:09PM +0100, Russell King - ARM Linux wrote:
> On Fri, Aug 30, 2013 at 11:07:28AM +0100, Sudeep KarkadaNagesha wrote:
> > On 29/08/13 15:55, Sudeep KarkadaNagesha wrote:
> > > From: Sudeep KarkadaNagesha <[email protected]>
> > >
> > > This patch series adds support to configure the rate and enable the
> > > event stream for architected timer. The event streams can be used to
> > > impose a timeout on a wfe, to safeguard against any programming error
> > > in case an expected event is not generated or even to implement
> > > wfe-based timeouts for userspace locking implementations. This feature
> > > can be disabled(enabled by default).
> > >
> > > Since the timer control register is reset to zero on warm boot, CPU
> > > PM notifier is added to save and restore the value.
> > >
> > Hi Russell,
> >
> > Can you have a look at this series ?
> > If you are OK, can I have your ACK on arm specific changes(PATCH 2/5) ?
>
> I think it would be more value to have someone from ARM Ltd ack it,
> because they will know the code much better than I do.
Looks good to me, so for patch 2/5:
Acked-by: Will Deacon <[email protected]>
Will
On 30/08/13 15:04, Will Deacon wrote:
> On Fri, Aug 30, 2013 at 12:43:09PM +0100, Russell King - ARM Linux wrote:
>> On Fri, Aug 30, 2013 at 11:07:28AM +0100, Sudeep KarkadaNagesha wrote:
>>> On 29/08/13 15:55, Sudeep KarkadaNagesha wrote:
>>>> From: Sudeep KarkadaNagesha <[email protected]>
>>>>
>>>> This patch series adds support to configure the rate and enable the
>>>> event stream for architected timer. The event streams can be used to
>>>> impose a timeout on a wfe, to safeguard against any programming error
>>>> in case an expected event is not generated or even to implement
>>>> wfe-based timeouts for userspace locking implementations. This feature
>>>> can be disabled(enabled by default).
>>>>
>>>> Since the timer control register is reset to zero on warm boot, CPU
>>>> PM notifier is added to save and restore the value.
>>>>
>>> Hi Russell,
>>>
>>> Can you have a look at this series ?
>>> If you are OK, can I have your ACK on arm specific changes(PATCH 2/5) ?
>>
>> I think it would be more value to have someone from ARM Ltd ack it,
>> because they will know the code much better than I do.
>
> Looks good to me, so for patch 2/5:
>
> Acked-by: Will Deacon <[email protected]>
>
Thanks Will and Russell.
Hi Catalin,
Can I have your ACK for ARM64 changes(PATCH 3/5) so that Daniel can
accept my pull request ?
Regards,
Sudeep
On Fri, Aug 30, 2013 at 04:46:17PM +0100, Sudeep KarkadaNagesha wrote:
> On 30/08/13 15:04, Will Deacon wrote:
> > On Fri, Aug 30, 2013 at 12:43:09PM +0100, Russell King - ARM Linux wrote:
> >> On Fri, Aug 30, 2013 at 11:07:28AM +0100, Sudeep KarkadaNagesha wrote:
> >>> On 29/08/13 15:55, Sudeep KarkadaNagesha wrote:
> >>>> From: Sudeep KarkadaNagesha <[email protected]>
> >>>>
> >>>> This patch series adds support to configure the rate and enable the
> >>>> event stream for architected timer. The event streams can be used to
> >>>> impose a timeout on a wfe, to safeguard against any programming error
> >>>> in case an expected event is not generated or even to implement
> >>>> wfe-based timeouts for userspace locking implementations. This feature
> >>>> can be disabled(enabled by default).
> >>>>
> >>>> Since the timer control register is reset to zero on warm boot, CPU
> >>>> PM notifier is added to save and restore the value.
> >>>>
> >>> Hi Russell,
> >>>
> >>> Can you have a look at this series ?
> >>> If you are OK, can I have your ACK on arm specific changes(PATCH 2/5) ?
> >>
> >> I think it would be more value to have someone from ARM Ltd ack it,
> >> because they will know the code much better than I do.
> >
> > Looks good to me, so for patch 2/5:
> >
> > Acked-by: Will Deacon <[email protected]>
> >
> Thanks Will and Russell.
>
> Hi Catalin,
>
> Can I have your ACK for ARM64 changes(PATCH 3/5) so that Daniel can
> accept my pull request ?
Well, I gave you my reviewed-by couple of times already. If you need
ack, here it is ;)
Acked-by: Catalin Marinas <[email protected]>