[PATCH 15/15] ARM: etm: Add sysfs entry to enable return stack if supported

John Stultz
2012-06-20T22:48:45Z

From: Arve Hjønnevåg <arve@android.com>

Add sysfs entry to enable return stack if supported

CC: Russell King <linux@arm.linux.org.uk>
CC: Paul Gortmaker <paul.gortmaker@windriver.com>
CC: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Acked-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
arch/arm/include/asm/hardware/coresight.h | 4 +++
arch/arm/kernel/etm.c | 51 +++++++++++++++++++++++++++--
2 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/hardware/coresight.h b/arch/arm/include/asm/hardware/coresight.h
index 727ba0f..dcf74d7 100644
--- a/arch/arm/include/asm/hardware/coresight.h
+++ b/arch/arm/include/asm/hardware/coresight.h
@@ -20,12 +20,14 @@
#define TRACER_TRACE_DATA_BIT 3
#define TRACER_TIMESTAMP_BIT 4
#define TRACER_BRANCHOUTPUT_BIT 5
+#define TRACER_RETURN_STACK_BIT 6
#define TRACER_ACCESSED BIT(TRACER_ACCESSED_BIT)
#define TRACER_RUNNING BIT(TRACER_RUNNING_BIT)
#define TRACER_CYCLE_ACC BIT(TRACER_CYCLE_ACC_BIT)
#define TRACER_TRACE_DATA BIT(TRACER_TRACE_DATA_BIT)
#define TRACER_TIMESTAMP BIT(TRACER_TIMESTAMP_BIT)
#define TRACER_BRANCHOUTPUT BIT(TRACER_BRANCHOUTPUT_BIT)
+#define TRACER_RETURN_STACK BIT(TRACER_RETURN_STACK_BIT)

#define TRACER_TIMEOUT 10000

@@ -62,6 +64,7 @@
#define ETMCTRL_BRANCH_OUTPUT (1 << 8)
#define ETMCTRL_CYCLEACCURATE (1 << 12)
#define ETMCTRL_TIMESTAMP_EN (1 << 28)
+#define ETMCTRL_RETURN_STACK_EN (1 << 29)

/* ETM configuration code register */
#define ETMR_CONFCODE (0x04)
@@ -136,6 +139,7 @@
#define ETMIDR_VERSION_PFT_1_0 0x30

#define ETMR_CCE 0x1e8
+#define ETMCCER_RETURN_STACK_IMPLEMENTED BIT(23)
#define ETMCCER_TIMESTAMPING_IMPLEMENTED BIT(22)

#define ETMR_TRACEIDR 0x200
diff --git a/arch/arm/kernel/etm.c b/arch/arm/kernel/etm.c
index 8e84d5c..c5fb6c9 100644
--- a/arch/arm/kernel/etm.c
+++ b/arch/arm/kernel/etm.c
@@ -124,6 +124,9 @@ static int trace_start_etm(struct tracectx *t, int id)
if (t->flags & TRACER_TIMESTAMP)
v |= ETMCTRL_TIMESTAMP_EN;

+ if (t->flags & TRACER_RETURN_STACK)
+ v |= ETMCTRL_RETURN_STACK_EN;
+
etm_unlock(t, id);

etm_writel(t, id, v, ETMR_CTRL);
@@ -703,10 +706,13 @@ static ssize_t trace_branch_output_store(struct kobject *kobj,
return -EINVAL;

mutex_lock(&tracer.mutex);
- if (branch_output)
+ if (branch_output) {
tracer.flags |= TRACER_BRANCHOUTPUT;
- else
+ /* Branch broadcasting is incompatible with the return stack */
+ tracer.flags &= ~TRACER_RETURN_STACK;
+ } else {
tracer.flags &= ~TRACER_BRANCHOUTPUT;
+ }
mutex_unlock(&tracer.mutex);

return n;
@@ -716,6 +722,39 @@ static struct kobj_attribute trace_branch_output_attr =
__ATTR(trace_branch_output, 0644,
trace_branch_output_show, trace_branch_output_store);

+static ssize_t trace_return_stack_show(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ char *buf)
+{
+ return sprintf(buf, "%d\n", !!(tracer.flags & TRACER_RETURN_STACK));
+}
+
+static ssize_t trace_return_stack_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t n)
+{
+ unsigned int return_stack;
+
+ if (sscanf(buf, "%u", &return_stack) != 1)
+ return -EINVAL;
+
+ mutex_lock(&tracer.mutex);
+ if (return_stack) {
+ tracer.flags |= TRACER_RETURN_STACK;
+ /* Return stack is incompatible with branch broadcasting */
+ tracer.flags &= ~TRACER_BRANCHOUTPUT;
+ } else {
+ tracer.flags &= ~TRACER_RETURN_STACK;
+ }
+ mutex_unlock(&tracer.mutex);
+
+ return n;
+}
+
+static struct kobj_attribute trace_return_stack_attr =
+ __ATTR(trace_return_stack, 0644,
+ trace_return_stack_show, trace_return_stack_store);
+
static ssize_t trace_timestamp_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
@@ -900,6 +939,14 @@ static int __devinit etm_probe(struct amba_device *dev, const struct amba_id *id
dev_dbg(&dev->dev,
"Failed to create trace_branch_output in sysfs\n");

+ if (etmccer & ETMCCER_RETURN_STACK_IMPLEMENTED) {
+ ret = sysfs_create_file(&dev->dev.kobj,
+ &trace_return_stack_attr.attr);
+ if (ret)
+ dev_dbg(&dev->dev,
+ "Failed to create trace_return_stack in sysfs\n");
+ }
+
if (etmccer & ETMCCER_TIMESTAMPING_IMPLEMENTED) {
ret = sysfs_create_file(&dev->dev.kobj,
&trace_timestamp_attr.attr);
--
1.7.9.5