ARM: 6834/1: perf: reset counters on all CPUs during initialisation

ARMv7 dictates that the interrupt-enable and count-enable registers for
each PMU counter are UNKNOWN following core reset.

This patch adds a new (optional) function pointer to struct arm_pmu for
resetting the PMU state during init. The reset function is called on
each CPU via an arch_initcall in the generic ARM perf_event code and
allows the PMU backend to write sane values to any UNKNOWN registers.

Acked-by: Jean Pihet <j-pihet@ti.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 30 insertions, 6 deletions

diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 22e194eb8536..e422f4c269a0 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -79,6 +79,7 @@ struct arm_pmu {
         void            (*write_counter)(int idx, u32 val);
         void            (*start)(void);
         void            (*stop)(void);
+        void            (*reset)(void *);
         const unsigned  (*cache_map)[PERF_COUNT_HW_CACHE_MAX]
                                     [PERF_COUNT_HW_CACHE_OP_MAX]
                                     [PERF_COUNT_HW_CACHE_RESULT_MAX];
@@ -624,6 +625,19 @@ static struct pmu pmu = {
 #include "perf_event_v6.c"
 #include "perf_event_v7.c"
 
+/*
+ * Ensure the PMU has sane values out of reset.
+ * This requires SMP to be available, so exists as a separate initcall.
+ */
+static int __init
+armpmu_reset(void)
+{
+        if (armpmu && armpmu->reset)
+                return on_each_cpu(armpmu->reset, NULL, 1);
+        return 0;
+}
+arch_initcall(armpmu_reset);
+
 static int __init
 init_hw_perf_events(void)
 {
diff --git a/arch/arm/kernel/perf_event_v7.c b/arch/arm/kernel/perf_event_v7.c
index d6c9dcd1979f..c08d07a99fcc 100644
--- a/arch/arm/kernel/perf_event_v7.c
+++ b/arch/arm/kernel/perf_event_v7.c
@@ -849,6 +849,18 @@ static int armv7pmu_get_event_idx(struct cpu_hw_events *cpuc,
         }
 }
 
+static void armv7pmu_reset(void *info)
+{
+        u32 idx, nb_cnt = armpmu->num_events;
+
+        /* The counter and interrupt enable registers are unknown at reset. */
+        for (idx = 1; idx < nb_cnt; ++idx)
+                armv7pmu_disable_event(NULL, idx);
+
+        /* Initialize & Reset PMNC: C and P bits */
+        armv7_pmnc_write(ARMV7_PMNC_P | ARMV7_PMNC_C);
+}
+
 static struct arm_pmu armv7pmu = {
         .handle_irq             = armv7pmu_handle_irq,
         .enable                 = armv7pmu_enable_event,
@@ -858,17 +870,15 @@ static struct arm_pmu armv7pmu = {
         .get_event_idx          = armv7pmu_get_event_idx,
         .start                  = armv7pmu_start,
         .stop                   = armv7pmu_stop,
+        .reset                  = armv7pmu_reset,
         .raw_event_mask         = 0xFF,
         .max_period             = (1LLU << 32) - 1,
 };
 
-static u32 __init armv7_reset_read_pmnc(void)
+static u32 __init armv7_read_num_pmnc_events(void)
 {
         u32 nb_cnt;
 
-        /* Initialize & Reset PMNC: C and P bits */
-        armv7_pmnc_write(ARMV7_PMNC_P | ARMV7_PMNC_C);
-
         /* Read the nb of CNTx counters supported from PMNC */
         nb_cnt = (armv7_pmnc_read() >> ARMV7_PMNC_N_SHIFT) & ARMV7_PMNC_N_MASK;
 
@@ -882,7 +892,7 @@ static const struct arm_pmu *__init armv7_a8_pmu_init(void)
         armv7pmu.name           = "ARMv7 Cortex-A8";
         armv7pmu.cache_map      = &armv7_a8_perf_cache_map;
         armv7pmu.event_map      = &armv7_a8_perf_map;
-        armv7pmu.num_events     = armv7_reset_read_pmnc();
+        armv7pmu.num_events     = armv7_read_num_pmnc_events();
         return &armv7pmu;
 }
 
@@ -892,7 +902,7 @@ static const struct arm_pmu *__init armv7_a9_pmu_init(void)
         armv7pmu.name           = "ARMv7 Cortex-A9";
         armv7pmu.cache_map      = &armv7_a9_perf_cache_map;
         armv7pmu.event_map      = &armv7_a9_perf_map;
-        armv7pmu.num_events     = armv7_reset_read_pmnc();
+        armv7pmu.num_events     = armv7_read_num_pmnc_events();
         return &armv7pmu;
 }
 #else