Re: [PATCH v1] drm/i915/selftests: Improve RC6 power measurement and error handling

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 11 Feb 2025, Sk Anirban <sk.anirban@intel.com> wrote:
> Improve RC6 power measurement and error handling. Add detailed error
> messages, and introduce a threshold check for RC6 residency.

Improve how? Why?

BR,
Jani.

>
> Signed-off-by: Sk Anirban <sk.anirban@intel.com>
> ---
>  drivers/gpu/drm/i915/gt/selftest_rc6.c | 61 +++++++++++++++++---------
>  1 file changed, 40 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/selftest_rc6.c b/drivers/gpu/drm/i915/gt/selftest_rc6.c
> index 908483ab0bc8..30bc2ff040ce 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_rc6.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_rc6.c
> @@ -33,15 +33,20 @@ int live_rc6_manual(void *arg)
>  {
>  	struct intel_gt *gt = arg;
>  	struct intel_rc6 *rc6 = &gt->rc6;
> -	u64 rc0_power, rc6_power;
> +	struct intel_rps *rps = &gt->rps;
>  	intel_wakeref_t wakeref;
> +	u64 sleep_time = 1000;
> +	u32 rc0_freq = 0;
> +	u32 rc6_freq = 0;
> +	u64 rc0_power[3];
> +	u64 rc6_power[3];
>  	bool has_power;
> +	u64 threshold;
>  	ktime_t dt;
>  	u64 res[2];
>  	int err = 0;
> -	u32 rc0_freq = 0;
> -	u32 rc6_freq = 0;
> -	struct intel_rps *rps = &gt->rps;
> +	u64 diff;
> +
>  
>  	/*
>  	 * Our claim is that we can "encourage" the GPU to enter rc6 at will.
> @@ -65,9 +70,9 @@ int live_rc6_manual(void *arg)
>  	res[0] = rc6_residency(rc6);
>  
>  	dt = ktime_get();
> -	rc0_power = librapl_energy_uJ();
> -	msleep(1000);
> -	rc0_power = librapl_energy_uJ() - rc0_power;
> +	rc0_power[0] = librapl_energy_uJ();
> +	msleep(sleep_time);
> +	rc0_power[1] = librapl_energy_uJ() - rc0_power[0];
>  	dt = ktime_sub(ktime_get(), dt);
>  	res[1] = rc6_residency(rc6);
>  	rc0_freq = intel_rps_read_actual_frequency_fw(rps);
> @@ -79,11 +84,12 @@ int live_rc6_manual(void *arg)
>  	}
>  
>  	if (has_power) {
> -		rc0_power = div64_u64(NSEC_PER_SEC * rc0_power,
> -				      ktime_to_ns(dt));
> -		if (!rc0_power) {
> +		rc0_power[2] = div64_u64(NSEC_PER_SEC * rc0_power[1],
> +					 ktime_to_ns(dt));
> +
> +		if (!rc0_power[2]) {
>  			if (rc0_freq)
> -				pr_debug("No power measured while in RC0! GPU Freq: %u in RC0\n",
> +				pr_debug("No power measured while in RC0! GPU Freq: %uMHz in RC0\n",
>  					 rc0_freq);
>  			else
>  				pr_err("No power and freq measured while in RC0\n");
> @@ -98,10 +104,10 @@ int live_rc6_manual(void *arg)
>  	res[0] = rc6_residency(rc6);
>  	intel_uncore_forcewake_flush(rc6_to_uncore(rc6), FORCEWAKE_ALL);
>  	dt = ktime_get();
> -	rc6_power = librapl_energy_uJ();
> -	msleep(1000);
> +	rc6_power[0] = librapl_energy_uJ();
> +	msleep(sleep_time);
>  	rc6_freq = intel_rps_read_actual_frequency_fw(rps);
> -	rc6_power = librapl_energy_uJ() - rc6_power;
> +	rc6_power[1] = librapl_energy_uJ() - rc6_power[0];
>  	dt = ktime_sub(ktime_get(), dt);
>  	res[1] = rc6_residency(rc6);
>  	if (res[1] == res[0]) {
> @@ -112,14 +118,27 @@ int live_rc6_manual(void *arg)
>  		err = -EINVAL;
>  	}
>  
> +	diff = res[1] - res[0];
> +	threshold = (9 * NSEC_PER_MSEC * sleep_time) / 10;
> +	if (diff < threshold) {
> +		pr_err("Did not enter RC6 properly, RC6 start residency=%lluns, RC6 end residency=%lluns\n",
> +		       res[0], res[1]);
> +		err = -EINVAL;
> +	}
> +
>  	if (has_power) {
> -		rc6_power = div64_u64(NSEC_PER_SEC * rc6_power,
> -				      ktime_to_ns(dt));
> -		pr_info("GPU consumed %llduW in RC0 and %llduW in RC6\n",
> -			rc0_power, rc6_power);
> -		if (2 * rc6_power > rc0_power) {
> -			pr_err("GPU leaked energy while in RC6! GPU Freq: %u in RC6 and %u in RC0\n",
> -			       rc6_freq, rc0_freq);
> +		rc6_power[2] = div64_u64(NSEC_PER_SEC * rc6_power[1],
> +					 ktime_to_ns(dt));
> +		pr_info("GPU consumed %lluuW in RC0 and %lluuW in RC6\n",
> +			rc0_power[2], rc6_power[2]);
> +
> +		if (2 * rc6_power[2] > rc0_power[2]) {
> +			pr_err("GPU leaked energy while in RC6!\n"
> +			       "GPU Freq: %uMHz in RC6 and %uMHz in RC0\n"
> +			       "RC0 energy before & after sleep respectively: %lluuJ %lluuJ\n"
> +			       "RC6 energy before & after sleep respectively: %lluuJ %lluuJ\n",
> +			       rc6_freq, rc0_freq, rc0_power[0], rc0_power[1],
> +			       rc6_power[0], rc6_power[1]);
>  			err = -EINVAL;
>  			goto out_unlock;
>  		}

-- 
Jani Nikula, Intel