Re: [PATCH v3] drm/i915/selftest: Add throttle reason diagnostics to RPS selftests

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

On Thu, Dec 18, 2025 at 11:16:29AM +0530, Anirban, Sk wrote:
> Hi Krzysztof,
> 
> Could you please let me know if I can retain your review for this version of
> my patch?

Yes, unless there are major changes we usually retain the tags.

> On 18-12-2025 11:02 am, 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)
> > v3: Extend throttle reasons debug support (Raag)
> > 
> > Signed-off-by: Sk Anirban <sk.anirban@intel.com>
> > ---
> >   drivers/gpu/drm/i915/gt/selftest_rps.c | 37 ++++++++++++++++++++++----
> >   1 file changed, 32 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..b42d9b39add6 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;
> >   	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));

Now that we allow 100 characters I think this can be one line.

> > +		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;
> >   	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));

Ditto.

> > +		throttle &= GT0_PERF_LIMIT_REASONS_MASK;
> > +
> >   		min.freq = rps->min_freq;
> >   		min.power = measure_power_at(rps, &min.freq);
> > @@ -1210,12 +1218,21 @@ int live_rps_power(void *arg)
> >   			pr_notice("Could not control frequency, ran at [%d:%uMHz, %d:%uMhz]\n",
> >   				  min.freq, intel_gpu_freq(rps, min.freq),
> >   				  max.freq, intel_gpu_freq(rps, max.freq));
> > +
> > +			if (throttle)
> > +				pr_warn("%s: GPU throttled with reasons 0x%08x\n",
> > +					engine->name, throttle);
> >   			continue;
> >   		}
> >   		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);
> > +
> >   			err = -EINVAL;
> >   			break;
> >   		}
> > @@ -1241,6 +1258,7 @@ int live_rps_dynamic(void *arg)
> >   	struct intel_engine_cs *engine;
> >   	enum intel_engine_id id;
> >   	struct igt_spinner spin;
> > +	u32 throttle;
> >   	int err = 0;
> >   	/*
> > @@ -1293,6 +1311,10 @@ 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));

Ditto. And with that,

Reviewed-by: Raag Jadav <raag.jadav@intel.com>

> > +		throttle &= GT0_PERF_LIMIT_REASONS_MASK;
> > +
> >   		igt_spinner_end(&spin);
> >   		min.dt = ktime_get();
> > @@ -1308,6 +1330,11 @@ 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;
> >   		}