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