ARM: etm: Add sysfs entry to enable return stack if supported

Change-Id: Icb73d60324ad0ddfc3e8a450a28bb3d90c702788
Signed-off-by: Arve Hjønnevåg <arve@android.com>

diff --git a/arch/arm/include/asm/hardware/coresight.h b/arch/arm/include/asm/hardware/coresight.h
index 025d20b95b299a2f1124f1b334c40b050911b987..4aee45da6d599501cc1afd08bc1bdf6593f240ec 100644 (file)
--- 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 af2a38b4f93aa7b580c8a14c3b4b3ddfe581761c..7db3247b218793b11d24fef048c56e6ba2bb7af8 100644 (file)
--- 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 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);