[Intel-gfx] [PATCH] drm/i915/selftests: Measure the energy consumed while in RC6

[Lucas De Marchi]

On Tue, Mar 24, 2020 at 1:45 PM Chris Wilson <chris at chris-wilson.co.uk> wrote:
>
> Measure and compare the energy consumed, as reported by the rapl MSR,
> by the GPU while in RC0 and RC6 states. Throw an error if RC6 does not
> at least halve the energy consumption of RC0, as this more than likely
> means we failed to enter RC0 correctly.
>
> If we can't measure the energy draw with the MSR, then it will report 0
> for both measurements. Since the measurement works on all gen6+, this seems
> worth flagging as an error.

I'm confused by this statement here. MSR is a *CPU* register and you are using
it here, mixed with RC6. How is that supposed to work with, e.g., dgfx?

thanks
Lucas De Marchi

>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Cc: Andi Shyti <andi.shyti at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/selftest_rc6.c | 39 ++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/gt/selftest_rc6.c b/drivers/gpu/drm/i915/gt/selftest_rc6.c
> index 95b165faeba7..3ac9a8925218 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_rc6.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_rc6.c
> @@ -12,6 +12,22 @@
>
>  #include "selftests/i915_random.h"
>
> +#define MCH_SECP_NRG_STTS              _MMIO(MCHBAR_MIRROR_BASE_SNB + 0x592c)
> +
> +static u64 energy_uJ(struct intel_rc6 *rc6)
> +{
> +       unsigned long long power;
> +       u32 units;
> +
> +       if (rdmsrl_safe(MSR_RAPL_POWER_UNIT, &power))
> +               return 0;
> +
> +       units = (power & 0x1f00) >> 8;
> +       power = intel_uncore_read_fw(rc6_to_uncore(rc6), MCH_SECP_NRG_STTS);
> +
> +       return (1000000 * power) >> units; /* convert to uJ */
> +}
> +
>  static u64 rc6_residency(struct intel_rc6 *rc6)
>  {
>         u64 result;
> @@ -31,7 +47,9 @@ int live_rc6_manual(void *arg)
>  {
>         struct intel_gt *gt = arg;
>         struct intel_rc6 *rc6 = &gt->rc6;
> +       u64 rc0_power, rc6_power;
>         intel_wakeref_t wakeref;
> +       ktime_t dt;
>         u64 res[2];
>         int err = 0;
>
> @@ -53,22 +71,35 @@ int live_rc6_manual(void *arg)
>         __intel_rc6_disable(rc6);
>         msleep(1); /* wakeup is not immediate, takes about 100us on icl */
>
> +       dt = ktime_get();
> +       rc0_power = energy_uJ(rc6);
>         res[0] = rc6_residency(rc6);
>         msleep(250);
>         res[1] = rc6_residency(rc6);
> +       rc0_power = div64_u64(energy_uJ(rc6) - rc0_power,
> +                             ktime_to_ns(ktime_sub(ktime_get(), dt)));
>         if ((res[1] - res[0]) >> 10) {
>                 pr_err("RC6 residency increased by %lldus while disabled for 250ms!\n",
>                        (res[1] - res[0]) >> 10);
>                 err = -EINVAL;
>                 goto out_unlock;
>         }
> +       if (!rc0_power) {
> +               pr_err("No power measured while in RC0\n");
> +               err = -EINVAL;
> +               goto out_unlock;
> +       }
>
>         /* Manually enter RC6 */
>         intel_rc6_park(rc6);
>
> +       dt = ktime_get();
> +       rc6_power = energy_uJ(rc6);
>         res[0] = rc6_residency(rc6);
>         msleep(100);
>         res[1] = rc6_residency(rc6);
> +       rc6_power = div64_u64(energy_uJ(rc6) - rc6_power,
> +                             ktime_to_ns(ktime_sub(ktime_get(), dt)));
>
>         if (res[1] == res[0]) {
>                 pr_err("Did not enter RC6! RC6_STATE=%08x, RC6_CONTROL=%08x, residency=%lld\n",
> @@ -78,6 +109,14 @@ int live_rc6_manual(void *arg)
>                 err = -EINVAL;
>         }
>
> +       pr_info("GPU consumed %llduW in RC0 and %llduW in RC6\n",
> +               rc0_power, rc6_power);
> +       if ((rc6_power >> 10) > (rc0_power >> 10) / 2) { /* compare mW */
> +               pr_err("GPU leaked energy while in RC6!\n");
> +               err = -EINVAL;
> +               goto out_unlock;
> +       }
> +
>         /* Restore what should have been the original state! */
>         intel_rc6_unpark(rc6);
>
> --
> 2.20.1
>
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