Re: [PATCH] drm/i915/selftest: Add throttle reason diagnostics to RPS selftests

[Raag Jadav <raag.jadav@intel.com>]

On Thu, Dec 11, 2025 at 11:20:46PM +0530, Sk Anirban wrote:
> Report GPU throttle reasons when RPS tests fail to reach expected
> frequencies or power levels.
> 
> v2: Read the throttle value before the spinner ends (Raag)
>     Add a condition before printing throttle value (Krzysztof)

Please also format-patch with same version for consistency.

https://kernelnewbies.org/FirstKernelPatch -> "Versioning one patch revision"

> Signed-off-by: Sk Anirban <sk.anirban@intel.com>
> ---
>  drivers/gpu/drm/i915/gt/selftest_rps.c | 33 ++++++++++++++++++++++----
>  1 file changed, 28 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/selftest_rps.c b/drivers/gpu/drm/i915/gt/selftest_rps.c
> index 73bc91c6ea07..b72536ea6747 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_rps.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_rps.c
> @@ -378,6 +378,7 @@ int live_rps_control(void *arg)
>  	enum intel_engine_id id;
>  	struct igt_spinner spin;
>  	intel_wakeref_t wakeref;
> +	u32 throttle = 0;

The test guarantees its assignment so no need to initialize it.

>  	int err = 0;
>  
>  	/*
> @@ -463,6 +464,10 @@ int live_rps_control(void *arg)
>  		max = rps_set_check(rps, limit);
>  		max_dt = ktime_sub(ktime_get(), max_dt);
>  
> +		throttle = intel_uncore_read(gt->uncore,
> +					     intel_gt_perf_limit_reasons_reg(gt));
> +		throttle &= GT0_PERF_LIMIT_REASONS_MASK;
> +
>  		min_dt = ktime_get();
>  		min = rps_set_check(rps, rps->min_freq);
>  		min_dt = ktime_sub(ktime_get(), min_dt);
> @@ -478,11 +483,9 @@ int live_rps_control(void *arg)
>  			min, max, ktime_to_ns(min_dt), ktime_to_ns(max_dt));
>  
>  		if (limit != rps->max_freq) {
> -			u32 throttle = intel_uncore_read(gt->uncore,
> -							 intel_gt_perf_limit_reasons_reg(gt));
> -
> -			pr_warn("%s: GPU throttled with reasons 0x%08x\n",
> -				engine->name, throttle & GT0_PERF_LIMIT_REASONS_MASK);
> +			if (throttle)
> +				pr_warn("%s: GPU throttled with reasons 0x%08x\n",
> +					engine->name, throttle);
>  			show_pstate_limits(rps);
>  		}
>  
> @@ -1138,6 +1141,7 @@ int live_rps_power(void *arg)
>  	struct intel_engine_cs *engine;
>  	enum intel_engine_id id;
>  	struct igt_spinner spin;
> +	u32 throttle = 0;

Ditto.

>  	int err = 0;
>  
>  	/*
> @@ -1195,6 +1199,10 @@ int live_rps_power(void *arg)
>  		max.freq = rps->max_freq;
>  		max.power = measure_power_at(rps, &max.freq);
>  
> +		throttle = intel_uncore_read(gt->uncore,
> +					     intel_gt_perf_limit_reasons_reg(gt));
> +		throttle &= GT0_PERF_LIMIT_REASONS_MASK;
> +
>  		min.freq = rps->min_freq;
>  		min.power = measure_power_at(rps, &min.freq);
>  
> @@ -1216,6 +1224,11 @@ int live_rps_power(void *arg)
>  		if (11 * min.power > 10 * max.power) {
>  			pr_err("%s: did not conserve power when setting lower frequency!\n",
>  			       engine->name);
> +
> +			if (throttle)
> +				pr_warn("%s: GPU throttled with reasons 0x%08x\n",
> +					engine->name, throttle);

I think this'll also be useful in frequency check above.

> +
>  			err = -EINVAL;
>  			break;
>  		}
> @@ -1241,6 +1254,7 @@ int live_rps_dynamic(void *arg)
>  	struct intel_engine_cs *engine;
>  	enum intel_engine_id id;
>  	struct igt_spinner spin;
> +	u32 throttle = 0;

Ditto.

Raag

>  	int err = 0;
>  
>  	/*
> @@ -1293,6 +1307,10 @@ int live_rps_dynamic(void *arg)
>  		max.freq = wait_for_freq(rps, rps->max_freq, 500);
>  		max.dt = ktime_sub(ktime_get(), max.dt);
>  
> +		throttle = intel_uncore_read(gt->uncore,
> +					     intel_gt_perf_limit_reasons_reg(gt));
> +		throttle &= GT0_PERF_LIMIT_REASONS_MASK;
> +
>  		igt_spinner_end(&spin);
>  
>  		min.dt = ktime_get();
> @@ -1308,6 +1326,11 @@ int live_rps_dynamic(void *arg)
>  		if (min.freq >= max.freq) {
>  			pr_err("%s: dynamic reclocking of spinner failed\n!",
>  			       engine->name);
> +
> +			if (throttle)
> +				pr_warn("%s: GPU throttled with reasons 0x%08x\n",
> +					engine->name, throttle);
> +
>  			err = -EINVAL;
>  		}
>  
> -- 
> 2.43.0
>