LinuxLists.cc - [PATCH v5 0/3] powerpc: powernv: Fastsleep workaround behavior

2015-04-15 06:24:29

Subject: [PATCH v5 0/3] powerpc: powernv: Fastsleep workaround behavior

2015-04-15 06:24:42

Subject: [PATCH v5 1/3] powerpc: Fix cpu_online_cores_map to return only online threads mask

Currently, cpu_online_cores_map returns a mask, which for every core with
at least one online thread, has the bit for thread 0 of the core set to 1,
and the bits for all other threads of the core set to 0. But thread 0 of
the core itself may not be online always. In such cases, if the returned
mask is used for IPI, then it'll cause IPIs to be skipped on cores where
the first thread is offline, because the IPI code refuses to send IPIs to
offline threads.

Fix this by setting the bit of the first online thread in the core.
This is done by fixing this in the underlying function
cpu_thread_mask_to_cores.

The result has the property that for all cores with online threads, there
is one bit set in the returned map. And further, all bits that are set in
the returned map correspond to online threads.

Signed-off-by: Shreyas B. Prabhu <[email protected]>
Reviewed-by: Preeti U Murthy <[email protected]>
[ Changelog from Michael Ellerman <[email protected]> ]
Reviewed-by: Gautham R. Shenoy <[email protected]>
---
arch/powerpc/include/asm/cputhreads.h | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/cputhreads.h b/arch/powerpc/include/asm/cputhreads.h
index 4c8ad59..1076d3f 100644
--- a/arch/powerpc/include/asm/cputhreads.h
+++ b/arch/powerpc/include/asm/cputhreads.h
@@ -31,9 +31,9 @@ extern cpumask_t threads_core_mask;
/* cpu_thread_mask_to_cores - Return a cpumask of one per cores
* hit by the argument
*
- * @threads: a cpumask of threads
+ * @threads: a cpumask of online threads
*
- * This function returns a cpumask which will have one "cpu" (or thread)
+ * This function returns a cpumask which will have one online cpu's
* bit set for each core that has at least one thread set in the argument.
*
* This can typically be used for things like IPI for tlb invalidations
@@ -42,13 +42,16 @@ extern cpumask_t threads_core_mask;
static inline cpumask_t cpu_thread_mask_to_cores(const struct cpumask *threads)
{
cpumask_t tmp, res;
- int i;
+ int i, cpu;

cpumask_clear(&res);
for (i = 0; i < NR_CPUS; i += threads_per_core) {
cpumask_shift_left(&tmp, &threads_core_mask, i);
- if (cpumask_intersects(threads, &tmp))
- cpumask_set_cpu(i, &res);
+ if (cpumask_intersects(threads, &tmp)) {
+ cpu = cpumask_next_and(-1, &tmp, cpu_online_mask);
+ if (cpu < nr_cpu_ids)
+ cpumask_set_cpu(cpu, &res);
+ }
}
return res;
}
--
1.9.3

2015-04-15 06:24:53

by Shreyas B. Prabhu

[permalink] [raw]

Subject: [PATCH v5 2/3] powerpc/powernv: Move cpuidle related code from setup.c to new file

This is a cleanup patch; doesn't change any functionality. Moves
all cpuidle related code from setup.c to a new file.

Signed-off-by: Shreyas B. Prabhu <[email protected]>
Reviewed-by: Preeti U Murthy <[email protected]>
---
arch/powerpc/platforms/powernv/Makefile | 2 +-
arch/powerpc/platforms/powernv/idle.c | 191 ++++++++++++++++++++++++++++++++
arch/powerpc/platforms/powernv/setup.c | 171 ----------------------------
3 files changed, 192 insertions(+), 172 deletions(-)
create mode 100644 arch/powerpc/platforms/powernv/idle.c

diff --git a/arch/powerpc/platforms/powernv/Makefile b/arch/powerpc/platforms/powernv/Makefile
index 33e44f3..bee9235 100644
--- a/arch/powerpc/platforms/powernv/Makefile
+++ b/arch/powerpc/platforms/powernv/Makefile
@@ -1,4 +1,4 @@
-obj-y += setup.o opal-wrappers.o opal.o opal-async.o
+obj-y += setup.o opal-wrappers.o opal.o opal-async.o idle.o
obj-y += opal-rtc.o opal-nvram.o opal-lpc.o opal-flash.o
obj-y += rng.o opal-elog.o opal-dump.o opal-sysparam.o opal-sensor.o
obj-y += opal-msglog.o opal-hmi.o opal-power.o
diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
new file mode 100644
index 0000000..104235a
--- /dev/null
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -0,0 +1,191 @@
+/*
+ * PowerNV cpuidle code
+ *
+ * Copyright 2015 IBM Corp.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+
+#include <asm/firmware.h>
+#include <asm/opal.h>
+#include <asm/cputhreads.h>
+#include <asm/cpuidle.h>
+#include <asm/code-patching.h>
+
+#include "powernv.h"
+#include "subcore.h"
+
+static u32 supported_cpuidle_states;
+
+int pnv_save_sprs_for_winkle(void)
+{
+ int cpu;
+ int rc;
+
+ /*
+ * hid0, hid1, hid4, hid5, hmeer and lpcr values are symmetric accross
+ * all cpus at boot. Get these reg values of current cpu and use the
+ * same accross all cpus.
+ */
+ uint64_t lpcr_val = mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1;
+ uint64_t hid0_val = mfspr(SPRN_HID0);
+ uint64_t hid1_val = mfspr(SPRN_HID1);
+ uint64_t hid4_val = mfspr(SPRN_HID4);
+ uint64_t hid5_val = mfspr(SPRN_HID5);
+ uint64_t hmeer_val = mfspr(SPRN_HMEER);
+
+ for_each_possible_cpu(cpu) {
+ uint64_t pir = get_hard_smp_processor_id(cpu);
+ uint64_t hsprg0_val = (uint64_t)&paca[cpu];
+
+ /*
+ * HSPRG0 is used to store the cpu's pointer to paca. Hence last
+ * 3 bits are guaranteed to be 0. Program slw to restore HSPRG0
+ * with 63rd bit set, so that when a thread wakes up at 0x100 we
+ * can use this bit to distinguish between fastsleep and
+ * deep winkle.
+ */
+ hsprg0_val |= 1;
+
+ rc = opal_slw_set_reg(pir, SPRN_HSPRG0, hsprg0_val);
+ if (rc != 0)
+ return rc;
+
+ rc = opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
+ if (rc != 0)
+ return rc;
+
+ /* HIDs are per core registers */
+ if (cpu_thread_in_core(cpu) == 0) {
+
+ rc = opal_slw_set_reg(pir, SPRN_HMEER, hmeer_val);
+ if (rc != 0)
+ return rc;
+
+ rc = opal_slw_set_reg(pir, SPRN_HID0, hid0_val);
+ if (rc != 0)
+ return rc;
+
+ rc = opal_slw_set_reg(pir, SPRN_HID1, hid1_val);
+ if (rc != 0)
+ return rc;
+
+ rc = opal_slw_set_reg(pir, SPRN_HID4, hid4_val);
+ if (rc != 0)
+ return rc;
+
+ rc = opal_slw_set_reg(pir, SPRN_HID5, hid5_val);
+ if (rc != 0)
+ return rc;
+ }
+ }
+
+ return 0;
+}
+
+static void pnv_alloc_idle_core_states(void)
+{
+ int i, j;
+ int nr_cores = cpu_nr_cores();
+ u32 *core_idle_state;
+
+ /*
+ * core_idle_state - First 8 bits track the idle state of each thread
+ * of the core. The 8th bit is the lock bit. Initially all thread bits
+ * are set. They are cleared when the thread enters deep idle state
+ * like sleep and winkle. Initially the lock bit is cleared.
+ * The lock bit has 2 purposes
+ * a. While the first thread is restoring core state, it prevents
+ * other threads in the core from switching to process context.
+ * b. While the last thread in the core is saving the core state, it
+ * prevents a different thread from waking up.
+ */
+ for (i = 0; i < nr_cores; i++) {
+ int first_cpu = i * threads_per_core;
+ int node = cpu_to_node(first_cpu);
+
+ core_idle_state = kmalloc_node(sizeof(u32), GFP_KERNEL, node);
+ *core_idle_state = PNV_CORE_IDLE_THREAD_BITS;
+
+ for (j = 0; j < threads_per_core; j++) {
+ int cpu = first_cpu + j;
+
+ paca[cpu].core_idle_state_ptr = core_idle_state;
+ paca[cpu].thread_idle_state = PNV_THREAD_RUNNING;
+ paca[cpu].thread_mask = 1 << j;
+ }
+ }
+
+ update_subcore_sibling_mask();
+
+ if (supported_cpuidle_states & OPAL_PM_WINKLE_ENABLED)
+ pnv_save_sprs_for_winkle();
+}
+
+u32 pnv_get_supported_cpuidle_states(void)
+{
+ return supported_cpuidle_states;
+}
+EXPORT_SYMBOL_GPL(pnv_get_supported_cpuidle_states);
+
+static int __init pnv_init_idle_states(void)
+{
+ struct device_node *power_mgt;
+ int dt_idle_states;
+ u32 *flags;
+ int i;
+
+ supported_cpuidle_states = 0;
+
+ if (cpuidle_disable != IDLE_NO_OVERRIDE)
+ goto out;
+
+ if (!firmware_has_feature(FW_FEATURE_OPALv3))
+ goto out;
+
+ power_mgt = of_find_node_by_path("/ibm,opal/power-mgt");
+ if (!power_mgt) {
+ pr_warn("opal: PowerMgmt Node not found\n");
+ goto out;
+ }
+ dt_idle_states = of_property_count_u32_elems(power_mgt,
+ "ibm,cpu-idle-state-flags");
+ if (dt_idle_states < 0) {
+ pr_warn("cpuidle-powernv: no idle states found in the DT\n");
+ goto out;
+ }
+
+ flags = kzalloc(sizeof(*flags) * dt_idle_states, GFP_KERNEL);
+ if (of_property_read_u32_array(power_mgt,
+ "ibm,cpu-idle-state-flags", flags, dt_idle_states)) {
+ pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-flags in DT\n");
+ goto out_free;
+ }
+
+ for (i = 0; i < dt_idle_states; i++)
+ supported_cpuidle_states |= flags[i];
+
+ if (!(supported_cpuidle_states & OPAL_PM_SLEEP_ENABLED_ER1)) {
+ patch_instruction(
+ (unsigned int *)pnv_fastsleep_workaround_at_entry,
+ PPC_INST_NOP);
+ patch_instruction(
+ (unsigned int *)pnv_fastsleep_workaround_at_exit,
+ PPC_INST_NOP);
+ }
+ pnv_alloc_idle_core_states();
+out_free:
+ kfree(flags);
+out:
+ return 0;
+}
+
+subsys_initcall(pnv_init_idle_states);
diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index 16fdcb2..509cdd2 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -35,12 +35,8 @@
#include <asm/opal.h>
#include <asm/kexec.h>
#include <asm/smp.h>
-#include <asm/cputhreads.h>
-#include <asm/cpuidle.h>
-#include <asm/code-patching.h>

#include "powernv.h"
-#include "subcore.h"

static void __init pnv_setup_arch(void)
{
@@ -277,173 +273,6 @@ static void __init pnv_setup_machdep_opal(void)
ppc_md.handle_hmi_exception = opal_handle_hmi_exception;
}

-static u32 supported_cpuidle_states;
-
-int pnv_save_sprs_for_winkle(void)
-{
- int cpu;
- int rc;
-
- /*
- * hid0, hid1, hid4, hid5, hmeer and lpcr values are symmetric accross
- * all cpus at boot. Get these reg values of current cpu and use the
- * same accross all cpus.
- */
- uint64_t lpcr_val = mfspr(SPRN_LPCR) & ~(u64)LPCR_PECE1;
- uint64_t hid0_val = mfspr(SPRN_HID0);
- uint64_t hid1_val = mfspr(SPRN_HID1);
- uint64_t hid4_val = mfspr(SPRN_HID4);
- uint64_t hid5_val = mfspr(SPRN_HID5);
- uint64_t hmeer_val = mfspr(SPRN_HMEER);
-
- for_each_possible_cpu(cpu) {
- uint64_t pir = get_hard_smp_processor_id(cpu);
- uint64_t hsprg0_val = (uint64_t)&paca[cpu];
-
- /*
- * HSPRG0 is used to store the cpu's pointer to paca. Hence last
- * 3 bits are guaranteed to be 0. Program slw to restore HSPRG0
- * with 63rd bit set, so that when a thread wakes up at 0x100 we
- * can use this bit to distinguish between fastsleep and
- * deep winkle.
- */
- hsprg0_val |= 1;
-
- rc = opal_slw_set_reg(pir, SPRN_HSPRG0, hsprg0_val);
- if (rc != 0)
- return rc;
-
- rc = opal_slw_set_reg(pir, SPRN_LPCR, lpcr_val);
- if (rc != 0)
- return rc;
-
- /* HIDs are per core registers */
- if (cpu_thread_in_core(cpu) == 0) {
-
- rc = opal_slw_set_reg(pir, SPRN_HMEER, hmeer_val);
- if (rc != 0)
- return rc;
-
- rc = opal_slw_set_reg(pir, SPRN_HID0, hid0_val);
- if (rc != 0)
- return rc;
-
- rc = opal_slw_set_reg(pir, SPRN_HID1, hid1_val);
- if (rc != 0)
- return rc;
-
- rc = opal_slw_set_reg(pir, SPRN_HID4, hid4_val);
- if (rc != 0)
- return rc;
-
- rc = opal_slw_set_reg(pir, SPRN_HID5, hid5_val);
- if (rc != 0)
- return rc;
- }
- }
-
- return 0;
-}
-
-static void pnv_alloc_idle_core_states(void)
-{
- int i, j;
- int nr_cores = cpu_nr_cores();
- u32 *core_idle_state;
-
- /*
- * core_idle_state - First 8 bits track the idle state of each thread
- * of the core. The 8th bit is the lock bit. Initially all thread bits
- * are set. They are cleared when the thread enters deep idle state
- * like sleep and winkle. Initially the lock bit is cleared.
- * The lock bit has 2 purposes
- * a. While the first thread is restoring core state, it prevents
- * other threads in the core from switching to process context.
- * b. While the last thread in the core is saving the core state, it
- * prevents a different thread from waking up.
- */
- for (i = 0; i < nr_cores; i++) {
- int first_cpu = i * threads_per_core;
- int node = cpu_to_node(first_cpu);
-
- core_idle_state = kmalloc_node(sizeof(u32), GFP_KERNEL, node);
- *core_idle_state = PNV_CORE_IDLE_THREAD_BITS;
-
- for (j = 0; j < threads_per_core; j++) {
- int cpu = first_cpu + j;
-
- paca[cpu].core_idle_state_ptr = core_idle_state;
- paca[cpu].thread_idle_state = PNV_THREAD_RUNNING;
- paca[cpu].thread_mask = 1 << j;
- }
- }
-
- update_subcore_sibling_mask();
-
- if (supported_cpuidle_states & OPAL_PM_WINKLE_ENABLED)
- pnv_save_sprs_for_winkle();
-}
-
-u32 pnv_get_supported_cpuidle_states(void)
-{
- return supported_cpuidle_states;
-}
-EXPORT_SYMBOL_GPL(pnv_get_supported_cpuidle_states);
-
-static int __init pnv_init_idle_states(void)
-{
- struct device_node *power_mgt;
- int dt_idle_states;
- u32 *flags;
- int i;
-
- supported_cpuidle_states = 0;
-
- if (cpuidle_disable != IDLE_NO_OVERRIDE)
- goto out;
-
- if (!firmware_has_feature(FW_FEATURE_OPALv3))
- goto out;
-
- power_mgt = of_find_node_by_path("/ibm,opal/power-mgt");
- if (!power_mgt) {
- pr_warn("opal: PowerMgmt Node not found\n");
- goto out;
- }
- dt_idle_states = of_property_count_u32_elems(power_mgt,
- "ibm,cpu-idle-state-flags");
- if (dt_idle_states < 0) {
- pr_warn("cpuidle-powernv: no idle states found in the DT\n");
- goto out;
- }
-
- flags = kzalloc(sizeof(*flags) * dt_idle_states, GFP_KERNEL);
- if (of_property_read_u32_array(power_mgt,
- "ibm,cpu-idle-state-flags", flags, dt_idle_states)) {
- pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-flags in DT\n");
- goto out_free;
- }
-
- for (i = 0; i < dt_idle_states; i++)
- supported_cpuidle_states |= flags[i];
-
- if (!(supported_cpuidle_states & OPAL_PM_SLEEP_ENABLED_ER1)) {
- patch_instruction(
- (unsigned int *)pnv_fastsleep_workaround_at_entry,
- PPC_INST_NOP);
- patch_instruction(
- (unsigned int *)pnv_fastsleep_workaround_at_exit,
- PPC_INST_NOP);
- }
- pnv_alloc_idle_core_states();
-out_free:
- kfree(flags);
-out:
- return 0;
-}
-
-subsys_initcall(pnv_init_idle_states);
-
static int __init pnv_probe(void)
{
unsigned long root = of_get_flat_dt_root();
--
1.9.3

2015-04-15 06:25:04

by Shreyas B. Prabhu

[permalink] [raw]

Subject: [PATCH v5 3/3] powerpc/powernv: Introduce sysfs control for fastsleep workaround behavior

Fastsleep is one of the idle state which cpuidle subsystem currently
uses on power8 machines. In this state L2 cache is brought down to a
threshold voltage. Therefore when the core is in fastsleep, the
communication between L2 and L3 needs to be fenced. But there is a bug
in the current power8 chips surrounding this fencing.

OPAL provides a workaround which precludes the possibility of hitting
this bug. But running with this workaround applied causes checkstop
if any correctable error in L2 cache directory is detected. Hence OPAL
also provides a way to undo the workaround.

In the existing implementation, workaround is applied by the last thread
of the core entering fastsleep and undone by the first thread waking up.
But this has a performance cost. These OPAL calls account for roughly
4000 cycles everytime the core has to enter or wakeup from fastsleep.

This patch introduces a sysfs attribute (fastsleep_workaround_state)
to choose the behavior of this workaround.

By default, fastsleep_workaround_state = dynamic. In this case, workaround
is applied/undone everytime the core enters/exits fastsleep.

fastsleep_workaround_state = applyonce. In this case the workaround is
applied once on all the cores and never undone. This can be triggered by
echo applyonce > /sys/devices/system/cpu/fastsleep_workaround_state

For simplicity this attribute can be modified only once. Implying, once
fastsleep_workaround_state is changed to applyonce, it cannot be reverted
to the default state.

Signed-off-by: Shreyas B. Prabhu <[email protected]>
---
arch/powerpc/include/asm/opal-api.h | 7 ++
arch/powerpc/include/asm/opal.h | 1 +
arch/powerpc/platforms/powernv/idle.c | 134 +++++++++++++++++++++++++
arch/powerpc/platforms/powernv/opal-wrappers.S | 1 +
4 files changed, 143 insertions(+)

diff --git a/arch/powerpc/include/asm/opal-api.h b/arch/powerpc/include/asm/opal-api.h
index 0321a90..a49e5fa 100644
--- a/arch/powerpc/include/asm/opal-api.h
+++ b/arch/powerpc/include/asm/opal-api.h
@@ -165,6 +165,13 @@
#define OPAL_PM_WINKLE_ENABLED 0x00040000
#define OPAL_PM_SLEEP_ENABLED_ER1 0x00080000 /* with workaround */

+/*
+ * OPAL_CONFIG_CPU_IDLE_STATE parameters
+ */
+#define OPAL_CONFIG_IDLE_FASTSLEEP 1
+#define OPAL_CONFIG_IDLE_UNDO 0
+#define OPAL_CONFIG_IDLE_APPLY 1
+
#ifndef __ASSEMBLY__

/* Other enums */
diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 042af1a..9a47813 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -186,6 +186,7 @@ int64_t opal_handle_hmi(void);
int64_t opal_register_dump_region(uint32_t id, uint64_t start, uint64_t end);
int64_t opal_unregister_dump_region(uint32_t id);
int64_t opal_slw_set_reg(uint64_t cpu_pir, uint64_t sprn, uint64_t val);
+int64_t opal_config_cpu_idle_state(uint64_t state, uint64_t flag);
int64_t opal_pci_set_phb_cxl_mode(uint64_t phb_id, uint64_t mode, uint64_t pe_number);
int64_t opal_ipmi_send(uint64_t interface, struct opal_ipmi_msg *msg,
uint64_t msg_len);
diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
index 104235a..eac7211 100644
--- a/arch/powerpc/platforms/powernv/idle.c
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -13,6 +13,8 @@
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/of.h>
+#include <linux/device.h>
+#include <linux/cpu.h>

#include <asm/firmware.h>
#include <asm/opal.h>
@@ -136,6 +138,129 @@ u32 pnv_get_supported_cpuidle_states(void)
}
EXPORT_SYMBOL_GPL(pnv_get_supported_cpuidle_states);

+
+static void pnv_fastsleep_workaround_apply(void *info)
+
+{
+ int rc;
+ int *err = info;
+
+ rc = opal_config_cpu_idle_state(OPAL_CONFIG_IDLE_FASTSLEEP,
+ OPAL_CONFIG_IDLE_APPLY);
+ if (rc)
+ *err = 1;
+}
+
+/*
+ * Used to store fastsleep workaround state
+ * 0 - Workaround applied/undone at fastsleep entry/exit path (Default)
+ * 1 - Workaround applied once, never undone.
+ */
+static u8 fastsleep_workaround_state;
+
+static const char * const fastsleep_workaround_avail_states[] = {
+ "dynamic", "applyonce"
+};
+
+/*
+ * fastsleep_workaround_avail_states values
+ */
+enum {
+ WORKAROUND_DYNAMIC,
+ WORKAROUND_APPLYONCE
+};
+static ssize_t show_fastsleep_workaround_state(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ char *s = buf;
+
+ if (fastsleep_workaround_state == 0) {
+ s += sprintf(s, "[%s] ",
+ fastsleep_workaround_avail_states[WORKAROUND_DYNAMIC]);
+ s += sprintf(s, "%s\n",
+ fastsleep_workaround_avail_states[WORKAROUND_APPLYONCE]);
+ } else {
+ s += sprintf(s, "%s ",
+ fastsleep_workaround_avail_states[WORKAROUND_DYNAMIC]);
+ s += sprintf(s, "[%s]\n",
+ fastsleep_workaround_avail_states[WORKAROUND_APPLYONCE]);
+ }
+ return (s - buf);
+}
+
+static ssize_t store_fastsleep_workaround_state(struct device *dev,
+ struct device_attribute *attr, const char *buf,
+ size_t count)
+{
+ cpumask_t primary_thread_mask;
+ int err;
+ int len;
+ char *p;
+ const char * const *s;
+
+ p = memchr(buf, '\n', count);
+ len = p ? p - buf : count;
+ s = &fastsleep_workaround_avail_states[WORKAROUND_APPLYONCE];
+ if (len != strlen(*s) || strncmp(buf, *s, len))
+ return -EINVAL;
+
+ /*
+ * If fastsleep_workaround_state already equals WORKAROUND_APPLYONCE,
+ * there is nothing to do.
+ */
+ if (fastsleep_workaround_state == WORKAROUND_APPLYONCE)
+ return count;
+
+ /*
+ * fastsleep_workaround_state = WORKAROUND_APPLYONCE implies
+ * fastsleep workaround needs to be left in 'applied' state on all
+ * the cores. Do this by-
+ * 1. Patching out the call to 'undo' workaround in fastsleep exit path
+ * 2. Sending ipi to all the cores which have atleast one online thread
+ * 3. Patching out the call to 'apply' workaround in fastsleep entry
+ * path
+ * There is no need to send ipi to cores which have all threads
+ * offlined, as last thread of the core entering fastsleep or deeper
+ * state would have applied workaround.
+ */
+ err = patch_instruction(
+ (unsigned int *)pnv_fastsleep_workaround_at_exit,
+ PPC_INST_NOP);
+ if (err) {
+ pr_err("fastsleep_workaround_state change failed while patching pnv_fastsleep_workaround_at_exit");
+ goto fail;
+ }
+
+ get_online_cpus();
+ primary_thread_mask = cpu_online_cores_map();
+ on_each_cpu_mask(&primary_thread_mask,
+ pnv_fastsleep_workaround_apply,
+ &err, 1);
+ put_online_cpus();
+ if (err) {
+ pr_err("fastsleep_workaround_state change failed while running pnv_fastsleep_workaround_apply");
+ goto fail;
+ }
+
+ err = patch_instruction(
+ (unsigned int *)pnv_fastsleep_workaround_at_entry,
+ PPC_INST_NOP);
+ if (err) {
+ pr_err("fastsleep_workaround_state change failed while patching pnv_fastsleep_workaround_at_entry");
+ goto fail;
+ }
+
+ fastsleep_workaround_state = WORKAROUND_APPLYONCE;
+
+ return count;
+fail:
+ return -EIO;
+}
+
+static DEVICE_ATTR(fastsleep_workaround_state, 0600,
+ show_fastsleep_workaround_state,
+ store_fastsleep_workaround_state);
+
static int __init pnv_init_idle_states(void)
{
struct device_node *power_mgt;
@@ -180,7 +305,16 @@ static int __init pnv_init_idle_states(void)
patch_instruction(
(unsigned int *)pnv_fastsleep_workaround_at_exit,
PPC_INST_NOP);
+ } else {
+ /*
+ * OPAL_PM_SLEEP_ENABLED_ER1 is set. It indicates that
+ * workaround is needed to use fastsleep. Provide sysfs
+ * control to choose how this workaround has to be applied.
+ */
+ device_create_file(cpu_subsys.dev_root,
+ &dev_attr_fastsleep_workaround_state);
}
+
pnv_alloc_idle_core_states();
out_free:
kfree(flags);
diff --git a/arch/powerpc/platforms/powernv/opal-wrappers.S b/arch/powerpc/platforms/powernv/opal-wrappers.S
index a7ade94..bf15ead 100644
--- a/arch/powerpc/platforms/powernv/opal-wrappers.S
+++ b/arch/powerpc/platforms/powernv/opal-wrappers.S
@@ -283,6 +283,7 @@ OPAL_CALL(opal_sensor_read, OPAL_SENSOR_READ);
OPAL_CALL(opal_get_param, OPAL_GET_PARAM);
OPAL_CALL(opal_set_param, OPAL_SET_PARAM);
OPAL_CALL(opal_handle_hmi, OPAL_HANDLE_HMI);
+OPAL_CALL(opal_config_cpu_idle_state, OPAL_CONFIG_CPU_IDLE_STATE);
OPAL_CALL(opal_slw_set_reg, OPAL_SLW_SET_REG);
OPAL_CALL(opal_register_dump_region, OPAL_REGISTER_DUMP_REGION);
OPAL_CALL(opal_unregister_dump_region, OPAL_UNREGISTER_DUMP_REGION);
--
1.9.3

2015-04-15 12:22:51

by Preeti U Murthy

[permalink] [raw]

Subject: Re: [PATCH v5 3/3] powerpc/powernv: Introduce sysfs control for fastsleep workaround behavior

On 04/15/2015 11:54 AM, Shreyas B. Prabhu wrote:
> +/*
> + * Used to store fastsleep workaround state
> + * 0 - Workaround applied/undone at fastsleep entry/exit path (Default)
> + * 1 - Workaround applied once, never undone.
> + */
> +static u8 fastsleep_workaround_state;
> +
> +static const char * const fastsleep_workaround_avail_states[] = {
> + "dynamic", "applyonce"
> +};
> +
> +/*
> + * fastsleep_workaround_avail_states values
> + */
> +enum {
> + WORKAROUND_DYNAMIC,
> + WORKAROUND_APPLYONCE
> +};

Is there a strong reason to use the above and not a boolean
fastsleep_workaround_once knob ? I also don't know what the user can
make out from 'dynamic'. Its not straight forward and is open to a great
deal of interpretation.

Why is this called the 'available' states. You can only echo applyonce
to it. And once applied it cannot be reverted. 'dynamic' is not a state
that is available to the user to choose. It is the default value. It is
therefore misleading.

My point is lets make the purpose and usage of this knob clear to the
user. Instead if we have fastsleep_workaround_once set to a default
value of 0. If it is 1, it is clear that the workaround is applied only
once. If it is '0' it is not the case and that it is repeatedly applied
somewhere.There are some advantages when we do this during printing of
errors as well. See below:

> + /*
> + * fastsleep_workaround_state = WORKAROUND_APPLYONCE implies
> + * fastsleep workaround needs to be left in 'applied' state on all
> + * the cores. Do this by-
> + * 1. Patching out the call to 'undo' workaround in fastsleep exit path
> + * 2. Sending ipi to all the cores which have atleast one online thread
> + * 3. Patching out the call to 'apply' workaround in fastsleep entry
> + * path
> + * There is no need to send ipi to cores which have all threads
> + * offlined, as last thread of the core entering fastsleep or deeper
> + * state would have applied workaround.
> + */
> + err = patch_instruction(
> + (unsigned int *)pnv_fastsleep_workaround_at_exit,
> + PPC_INST_NOP);
> + if (err) {
> + pr_err("fastsleep_workaround_state change failed while patching pnv_fastsleep_workaround_at_exit");
> + goto fail;
> + }
> +
> + get_online_cpus();
> + primary_thread_mask = cpu_online_cores_map();
> + on_each_cpu_mask(&primary_thread_mask,
> + pnv_fastsleep_workaround_apply,
> + &err, 1);
> + put_online_cpus();
> + if (err) {
> + pr_err("fastsleep_workaround_state change failed while running pnv_fastsleep_workaround_apply");
> + goto fail;
> + }

> +
> + err = patch_instruction(
> + (unsigned int *)pnv_fastsleep_workaround_at_entry,
> + PPC_INST_NOP);
> + if (err) {
> + pr_err("fastsleep_workaround_state change failed while patching pnv_fastsleep_workaround_at_entry");
> + goto fail;
> + }

Now in all the above error conditions, we know that the workaround will
end up being applied always. But the error messages don't indicate that
since it says state change failed. state change to 'what' failed? I
understand that the user in question can make sense of it, but it seems
to indicate that there is a state machine in question and that the user
can rotate among them, when there is only one state that he can choose.
If we instead use fastsleep_workaround_once, all the above error
messages will simply fallback to 'fastsleep_workaround_once failed',
which indicates clearly that the workaround will be repeatedly applied
somewhere. When the user tries to echo a '0' after a 1, we can fail with
"fastsleep_workaround_once cannot be reverted", indicating its applied
once now and nothing can be done about it.

Thus the consequence of every action of the user becomes explicit,
informing even a clueless user what can be done with this knob IMO.

Regards
Preeti U Murthy
> +
> + fastsleep_workaround_state = WORKAROUND_APPLYONCE;
> +
> + return count;
> +fail:
> + return -EIO;
> +}
> +
> +static DEVICE_ATTR(fastsleep_workaround_state, 0600,
> + show_fastsleep_workaround_state,
> + store_fastsleep_workaround_state);
> +
> static int __init pnv_init_idle_states(void)
> {
> struct device_node *power_mgt;
> @@ -180,7 +305,16 @@ static int __init pnv_init_idle_states(void)
> patch_instruction(
> (unsigned int *)pnv_fastsleep_workaround_at_exit,
> PPC_INST_NOP);
> + } else {
> + /*
> + * OPAL_PM_SLEEP_ENABLED_ER1 is set. It indicates that
> + * workaround is needed to use fastsleep. Provide sysfs
> + * control to choose how this workaround has to be applied.
> + */
> + device_create_file(cpu_subsys.dev_root,
> + &dev_attr_fastsleep_workaround_state);
> }
> +
> pnv_alloc_idle_core_states();
> out_free:
> kfree(flags);
> diff --git a/arch/powerpc/platforms/powernv/opal-wrappers.S b/arch/powerpc/platforms/powernv/opal-wrappers.S
> index a7ade94..bf15ead 100644
> --- a/arch/powerpc/platforms/powernv/opal-wrappers.S
> +++ b/arch/powerpc/platforms/powernv/opal-wrappers.S
> @@ -283,6 +283,7 @@ OPAL_CALL(opal_sensor_read, OPAL_SENSOR_READ);
> OPAL_CALL(opal_get_param, OPAL_GET_PARAM);
> OPAL_CALL(opal_set_param, OPAL_SET_PARAM);
> OPAL_CALL(opal_handle_hmi, OPAL_HANDLE_HMI);
> +OPAL_CALL(opal_config_cpu_idle_state, OPAL_CONFIG_CPU_IDLE_STATE);
> OPAL_CALL(opal_slw_set_reg, OPAL_SLW_SET_REG);
> OPAL_CALL(opal_register_dump_region, OPAL_REGISTER_DUMP_REGION);
> OPAL_CALL(opal_unregister_dump_region, OPAL_UNREGISTER_DUMP_REGION);
>