[PATCH V3 1/1] ARM: perf: Set suniden bit

[George G. Davis]

From: Martin Fuzzey <mfuzzey at parkeon.com>

Counters other than the CPU cycle counter only work if the security module
SUNIDEN bit is set.

Since access to this register is only possible in secure mode it will
only be done if the device tree property "secure-reg-access" is set.

Without this:
# perf stat -e cycles,instructions sleep 1

 Performance counter stats for 'sleep 1':

          14606094 cycles                    #    0.000 GHz
                 0 instructions              #    0.00  insns per cycle

After applying:
# perf stat -e cycles,instructions sleep 1

 Performance counter stats for 'sleep 1':

           5843809      cycles                   
           2566484      instructions              #    0.44  insns per cycle        

       1.020144000 seconds time elapsed


Some platforms (eg i.MX53) may also need additional platform specific setup.

Signed-off-by: Martin Fuzzey <mfuzzey at parkeon.com>
Signed-off-by: Pooya Keshavarzi <Pooya.Keshavarzi at de.bosch.com>
Signed-off-by: George G. Davis <george_davis at mentor.com>
---

Changes in v3:
- Pooya Keshavarzi:
  * v2 review comment fixups
  * Use on_each_cpu() to set SUNIDEN on all CPUs
  * Move armv7pmu_enable_secure_access() call from armv7pmu_start() to
    armv7_a8_map_event() such that is called only once instead of each
    time `perf` is executed
- George G. Davis:
  * Fixup to apply after file renames due to commit fa8ad78 (arm: perf:
    factor arm_pmu core out to drivers)
  * Fix checkpatch 'CHECK: Prefer using the BIT macro' issue

 Documentation/devicetree/bindings/arm/pmu.txt |  8 ++++++++
 arch/arm/kernel/perf_event_v7.c               | 17 +++++++++++++++++
 drivers/perf/arm_pmu.c                        |  3 +++
 include/linux/perf/arm_pmu.h                  |  1 +
 4 files changed, 29 insertions(+)

diff --git a/Documentation/devicetree/bindings/arm/pmu.txt b/Documentation/devicetree/bindings/arm/pmu.txt
index 97ba45a..8d4b831 100644
--- a/Documentation/devicetree/bindings/arm/pmu.txt
+++ b/Documentation/devicetree/bindings/arm/pmu.txt
@@ -45,6 +45,14 @@ Optional properties:
 - qcom,no-pc-write : Indicates that this PMU doesn't support the 0xc and 0xd
                      events.
 
+- secure-reg-access : Indicates that secure mode access is available.
+		This will cause the driver to do any setup required that
+		is only possible in secure mode.
+		If not present the secure registers will not be touched,
+		which means the PMU may fail to operate unless external
+		code (bootloader or security monitor) has performed the
+		appropriate initialisation.
+
 Example:
 
 pmu {
diff --git a/arch/arm/kernel/perf_event_v7.c b/arch/arm/kernel/perf_event_v7.c
index 126dc67..8dc5582 100644
--- a/arch/arm/kernel/perf_event_v7.c
+++ b/arch/arm/kernel/perf_event_v7.c
@@ -600,6 +600,11 @@ static const unsigned scorpion_perf_cache_map[PERF_COUNT_HW_CACHE_MAX]
 #define	ARMV7_EXCLUDE_USER	(1 << 30)
 #define	ARMV7_INCLUDE_HYP	(1 << 27)
 
+/*
+ * Secure debug enable reg
+ */
+#define ARMV7_SDER_SUNIDEN	BIT(1) /* Permit non-invasive debug */
+
 static inline u32 armv7_pmnc_read(void)
 {
 	u32 val;
@@ -994,6 +999,15 @@ static void armv7pmu_reset(void *info)
 	armv7_pmnc_write(ARMV7_PMNC_P | ARMV7_PMNC_C);
 }
 
+static void armv7pmu_enable_secure_access(void *data)
+{
+	u32 val;
+
+	asm volatile("mrc p15, 0, %0, c1, c1, 1" : "=r" (val));
+	val |= ARMV7_SDER_SUNIDEN;
+	asm volatile("mcr p15, 0, %0, c1, c1, 1" : : "r" (val));
+}
+
 static int armv7_a8_map_event(struct perf_event *event)
 {
 	return armpmu_map_event(event, &armv7_a8_perf_map,
@@ -1060,6 +1074,9 @@ static void armv7pmu_init(struct arm_pmu *cpu_pmu)
 	cpu_pmu->stop		= armv7pmu_stop;
 	cpu_pmu->reset		= armv7pmu_reset;
 	cpu_pmu->max_period	= (1LLU << 32) - 1;
+
+	if (cpu_pmu->secure_access)
+		on_each_cpu(armv7pmu_enable_secure_access, NULL, 1);
 };
 
 static void armv7_read_num_pmnc_events(void *info)
diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index be3755c..972e6b7 100644
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -895,6 +895,9 @@ int arm_pmu_device_probe(struct platform_device *pdev,
 	if (node && (of_id = of_match_node(of_table, pdev->dev.of_node))) {
 		init_fn = of_id->data;
 
+		pmu->secure_access = of_property_read_bool(pdev->dev.of_node,
+							   "secure-reg-access");
+
 		ret = of_pmu_irq_cfg(pmu);
 		if (!ret)
 			ret = init_fn(pmu);
diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
index bfa673b..4b8dc13 100644
--- a/include/linux/perf/arm_pmu.h
+++ b/include/linux/perf/arm_pmu.h
@@ -104,6 +104,7 @@ struct arm_pmu {
 	atomic_t	active_events;
 	struct mutex	reserve_mutex;
 	u64		max_period;
+	bool		secure_access;
 	struct platform_device	*plat_device;
 	struct pmu_hw_events	__percpu *hw_events;
 	struct notifier_block	hotplug_nb;
-- 
1.9.3