Re: [PATCH i-g-t v2 4/4] tests/intel/xe_oa: Add an option to capture register accesses in ftrace

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Tue, 26 Aug 2025 15:43:01 -0700, Umesh Nerlige Ramappa wrote:
>
> Capture ftrace with the --trace option when needed. This is not intended
> to run as default, but more of a debug functionality when manually
> running individual tests.
>
> v2: (Ashutosh)
> - Update commit title
> - Check ftrace buffer size sooner. Use defaults
> - s/Mb/MB
> - x 1024 instead of x 1000

Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>

>
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
> ---
>  tests/intel/xe_oa.c | 63 ++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 62 insertions(+), 1 deletion(-)
>
> diff --git a/tests/intel/xe_oa.c b/tests/intel/xe_oa.c
> index 24442e4b83c6..2fb7c332226e 100644
> --- a/tests/intel/xe_oa.c
> +++ b/tests/intel/xe_oa.c
> @@ -307,6 +307,8 @@ static struct oa_format lnl_oa_formats[XE_OA_FORMAT_MAX] = {
>		.bc_report = 0 },
>  };
>
> +static bool oa_trace = false;
> +static uint32_t oa_trace_buf_mb = 1;
>  static int drm_fd = -1;
>  static int sysfs = -1;
>  static int pm_fd = -1;
> @@ -389,6 +391,31 @@ static u32 get_stream_status(int fd)
>	return status.oa_status;
>  }
>
> +static void enable_trace_log(void)
> +{
> +	char cmd[64] = {0};
> +
> +	if (!oa_trace)
> +		return;
> +
> +	snprintf(cmd, sizeof(cmd) - 1, "echo %d > /sys/kernel/debug/tracing/buffer_size_kb", oa_trace_buf_mb * 1024);
> +	system(cmd);
> +	system("echo 0 > /sys/kernel/debug/tracing/tracing_on");
> +	system("echo > /sys/kernel/debug/tracing/trace");
> +	system("echo 1 > /sys/kernel/debug/tracing/events/xe/enable");
> +	system("echo 1 > /sys/kernel/debug/tracing/events/xe/xe_reg_rw/enable");
> +	system("echo 1 > /sys/kernel/debug/tracing/tracing_on");
> +}
> +
> +static void disable_trace_log(void)
> +{
> +	if (!oa_trace)
> +		return;
> +
> +	system("echo 0 > /sys/kernel/debug/tracing/tracing_on");
> +	system("cat /sys/kernel/debug/tracing/trace");
> +}
> +
>  static void
>  dump_report(const uint32_t *report, uint32_t size, const char *message) {
>	uint32_t i;
> @@ -4958,7 +4985,39 @@ static const char *xe_engine_class_name(uint32_t engine_class)
>	igt_require_f(hwe, "no render engine\n"); \
>	igt_dynamic_f("rcs-%d", hwe->engine_instance)
>
> -igt_main
> +static int opt_handler(int opt, int opt_index, void *data)
> +{
> +	uint32_t tmp;
> +
> +	switch (opt) {
> +	case 'b':
> +		tmp = strtoul(optarg, NULL, 0);
> +		if (tmp <= 20 && tmp >= 1)
> +			oa_trace_buf_mb = tmp;
> +
> +		igt_debug("Trace buffer %d Mb\n", oa_trace_buf_mb);
> +		break;
> +	case 't':
> +		oa_trace = true;
> +		igt_debug("Trace enabled\n");
> +		break;
> +	default:
> +		return IGT_OPT_HANDLER_ERROR;
> +	}
> +
> +	return IGT_OPT_HANDLER_SUCCESS;
> +}
> +
> +static const char *help_str =  "  --trace		| -t\t\tEnable ftrace\n"
> +			       "  --trace_buf_size_mb	| -b\t\tSet ftrace buffer size in MB (default = 1, min = 1, max = 20)\n";
> +
> +static struct option long_options[] = {
> +	{"trace", 0, 0, 't'},
> +	{"trace_buf_size_mb", 0, 0, 'b'},
> +	{ NULL, 0, 0, 0 }
> +};
> +
> +igt_main_args("b:t", long_options, help_str, opt_handler, NULL)
>  {
>	const struct sync_section {
>		const char *name;
> @@ -5002,6 +5061,7 @@ igt_main
>		 */
>		igt_assert_eq(drm_fd, -1);
>
> +		enable_trace_log();
>		drm_fd = drm_open_driver(DRIVER_XE);
>		xe_dev = xe_device_get(drm_fd);
>
> @@ -5235,5 +5295,6 @@ igt_main
>			intel_xe_perf_free(intel_xe_perf);
>
>		drm_close_driver(drm_fd);
> +		disable_trace_log();
>	}
>  }
> --
> 2.43.0
>