Re: [PATCH v3] drm/i915/selftests: Refactor RC6 power measurement and error handling

["Nilawar, Badal" <badal.nilawar@intel.com>]

On 07-03-2025 00:41, sk.anirban@intel.com wrote:
> From: Sk Anirban <sk.anirban@intel.com>
>
> Refactor power measurement logic to store and compare energy values.
> Introduce a threshold check to ensure the GPU enters RC6 properly.
>
> v2:
>    - Improved commit message (Badal)
>
> v3:
>   - Reorder threshold check (Badal)
>
> Signed-off-by: Sk Anirban <sk.anirban@intel.com>
> ---
>   drivers/gpu/drm/i915/gt/selftest_rc6.c | 59 +++++++++++++++++---------
>   1 file changed, 38 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..5364e50be638 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]) {
> @@ -113,13 +119,24 @@ int live_rc6_manual(void *arg)
>   	}
>   
>   	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]);
> +
> +			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]);

Check if BAT failures reported are related. Similar errors were seen 
with other selftest related patches too.
Otherwise this looks good to me.

Reviewed-by: Badal Nilawar <badal.nilawar@intel.com>

Regards,
Badal

>   			err = -EINVAL;
>   			goto out_unlock;
>   		}