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Subject[PATCH v2] ARM: perf: save/restore pmu registers in pm notifier
Date
From: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>

This adds core support for saving and restoring CPU PMU registers
for suspend/resume support i.e. deeper C-states in cpuidle terms.
This patch adds support only to ARMv7 PMU registers save/restore.
It needs to be extended to xscale and ARMv6 if needed.

[Neil] We found that DS-5 not work on our CA7 based SoCs.
After debuging, found PMU registers were lost because of core power down.
Then i found Sudeep had a patch to fix it about two years ago but not in
the mainline, just port it.

Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
Signed-off-by: Neil Zhang <zhangwm@marvell.com>
---
arch/arm/include/asm/pmu.h | 11 +++++++++
arch/arm/kernel/perf_event_cpu.c | 29 ++++++++++++++++++++++-
arch/arm/kernel/perf_event_v7.c | 47 ++++++++++++++++++++++++++++++++++++++
3 files changed, 86 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/pmu.h b/arch/arm/include/asm/pmu.h
index ae1919b..f37f048 100644
--- a/arch/arm/include/asm/pmu.h
+++ b/arch/arm/include/asm/pmu.h
@@ -62,6 +62,15 @@ struct pmu_hw_events {
raw_spinlock_t pmu_lock;
};

+struct cpupmu_regs {
+ u32 pmc;
+ u32 pmcntenset;
+ u32 pmuseren;
+ u32 pmintenset;
+ u32 pmxevttype[8];
+ u32 pmxevtcnt[8];
+};
+
struct arm_pmu {
struct pmu pmu;
cpumask_t active_irqs;
@@ -83,6 +92,8 @@ struct arm_pmu {
int (*request_irq)(struct arm_pmu *, irq_handler_t handler);
void (*free_irq)(struct arm_pmu *);
int (*map_event)(struct perf_event *event);
+ void (*save_regs)(struct arm_pmu *, struct cpupmu_regs *);
+ void (*restore_regs)(struct arm_pmu *, struct cpupmu_regs *);
int num_events;
atomic_t active_events;
struct mutex reserve_mutex;
diff --git a/arch/arm/kernel/perf_event_cpu.c b/arch/arm/kernel/perf_event_cpu.c
index 51798d7..7f1c756 100644
--- a/arch/arm/kernel/perf_event_cpu.c
+++ b/arch/arm/kernel/perf_event_cpu.c
@@ -19,6 +19,7 @@
#define pr_fmt(fmt) "CPU PMU: " fmt

#include <linux/bitmap.h>
+#include <linux/cpu_pm.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/of.h>
@@ -39,6 +40,7 @@ static DEFINE_PER_CPU(struct arm_pmu *, percpu_pmu);
static DEFINE_PER_CPU(struct perf_event * [ARMPMU_MAX_HWEVENTS], hw_events);
static DEFINE_PER_CPU(unsigned long [BITS_TO_LONGS(ARMPMU_MAX_HWEVENTS)], used_mask);
static DEFINE_PER_CPU(struct pmu_hw_events, cpu_hw_events);
+static DEFINE_PER_CPU(struct cpupmu_regs, cpu_pmu_regs);

/*
* Despite the names, these two functions are CPU-specific and are used
@@ -217,6 +219,23 @@ static struct notifier_block cpu_pmu_hotplug_notifier = {
.notifier_call = cpu_pmu_notify,
};

+static int cpu_pmu_pm_notify(struct notifier_block *b,
+ unsigned long action, void *hcpu)
+{
+ struct cpupmu_regs *pmuregs = this_cpu_ptr(&cpu_pmu_regs);
+
+ if (action == CPU_PM_ENTER && cpu_pmu->save_regs)
+ cpu_pmu->save_regs(cpu_pmu, pmuregs);
+ else if (action == CPU_PM_EXIT && cpu_pmu->restore_regs)
+ cpu_pmu->restore_regs(cpu_pmu, pmuregs);
+
+ return NOTIFY_OK;
+}
+
+static struct notifier_block cpu_pmu_pm_notifier = {
+ .notifier_call = cpu_pmu_pm_notify,
+};
+
/*
* PMU platform driver and devicetree bindings.
*/
@@ -349,9 +368,17 @@ static int __init register_pmu_driver(void)
if (err)
return err;

+ err = cpu_pm_register_notifier(&cpu_pmu_pm_notifier);
+ if (err) {
+ unregister_cpu_notifier(&cpu_pmu_hotplug_notifier);
+ return err;
+ }
+
err = platform_driver_register(&cpu_pmu_driver);
- if (err)
+ if (err) {
+ cpu_pm_unregister_notifier(&cpu_pmu_pm_notifier);
unregister_cpu_notifier(&cpu_pmu_hotplug_notifier);
+ }

return err;
}
diff --git a/arch/arm/kernel/perf_event_v7.c b/arch/arm/kernel/perf_event_v7.c
index f4ef398..29ae8f1 100644
--- a/arch/arm/kernel/perf_event_v7.c
+++ b/arch/arm/kernel/perf_event_v7.c
@@ -1237,6 +1237,51 @@ static void armv7_pmnc_dump_regs(struct arm_pmu *cpu_pmu)
}
#endif

+static void armv7pmu_save_regs(struct arm_pmu *cpu_pmu,
+ struct cpupmu_regs *regs)
+{
+ unsigned int cnt;
+ asm volatile("mrc p15, 0, %0, c9, c12, 0" : "=r" (regs->pmc));
+ if (!(regs->pmc & ARMV7_PMNC_E))
+ return;
+
+ asm volatile("mrc p15, 0, %0, c9, c12, 1" : "=r" (regs->pmcntenset));
+ asm volatile("mrc p15, 0, %0, c9, c14, 0" : "=r" (regs->pmuseren));
+ asm volatile("mrc p15, 0, %0, c9, c14, 1" : "=r" (regs->pmintenset));
+ asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r" (regs->pmxevtcnt[0]));
+ for (cnt = ARMV7_IDX_COUNTER0;
+ cnt <= ARMV7_IDX_COUNTER_LAST(cpu_pmu); cnt++) {
+ armv7_pmnc_select_counter(cnt);
+ asm volatile("mrc p15, 0, %0, c9, c13, 1"
+ : "=r"(regs->pmxevttype[cnt]));
+ asm volatile("mrc p15, 0, %0, c9, c13, 2"
+ : "=r"(regs->pmxevtcnt[cnt]));
+ }
+ return;
+}
+
+static void armv7pmu_restore_regs(struct arm_pmu *cpu_pmu,
+ struct cpupmu_regs *regs)
+{
+ unsigned int cnt;
+ if (!(regs->pmc & ARMV7_PMNC_E))
+ return;
+
+ asm volatile("mcr p15, 0, %0, c9, c12, 1" : : "r" (regs->pmcntenset));
+ asm volatile("mcr p15, 0, %0, c9, c14, 0" : : "r" (regs->pmuseren));
+ asm volatile("mcr p15, 0, %0, c9, c14, 1" : : "r" (regs->pmintenset));
+ asm volatile("mcr p15, 0, %0, c9, c13, 0" : : "r" (regs->pmxevtcnt[0]));
+ for (cnt = ARMV7_IDX_COUNTER0;
+ cnt <= ARMV7_IDX_COUNTER_LAST(cpu_pmu); cnt++) {
+ armv7_pmnc_select_counter(cnt);
+ asm volatile("mcr p15, 0, %0, c9, c13, 1"
+ : : "r"(regs->pmxevttype[cnt]));
+ asm volatile("mcr p15, 0, %0, c9, c13, 2"
+ : : "r"(regs->pmxevtcnt[cnt]));
+ }
+ asm volatile("mcr p15, 0, %0, c9, c12, 0" : : "r" (regs->pmc));
+}
+
static void armv7pmu_enable_event(struct perf_event *event)
{
unsigned long flags;
@@ -1528,6 +1573,8 @@ static void armv7pmu_init(struct arm_pmu *cpu_pmu)
cpu_pmu->start = armv7pmu_start;
cpu_pmu->stop = armv7pmu_stop;
cpu_pmu->reset = armv7pmu_reset;
+ cpu_pmu->save_regs = armv7pmu_save_regs;
+ cpu_pmu->restore_regs = armv7pmu_restore_regs;
cpu_pmu->max_period = (1LLU << 32) - 1;
};

--
1.7.9.5


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