[Intel-gfx] [PATCH 3/7] drm/i915/icl: Apply recommended rc6 idle hysteresis

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> Quoting Mika Kuoppala (2019-04-09 17:13:06)
>> Use a recommended idle hysteresis for media and render powergates.
>> 
>> References: bspec#52070
>> Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
>> ---
>>  drivers/gpu/drm/i915/intel_pm.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
>> index 30ef507b88a4..b9be9ea5fc18 100644
>> --- a/drivers/gpu/drm/i915/intel_pm.c
>> +++ b/drivers/gpu/drm/i915/intel_pm.c
>> @@ -7170,8 +7170,8 @@ static void gen11_enable_rc6(struct drm_i915_private *dev_priv)
>>          * conservative, we have to factor in a context switch on top (due
>>          * to ksoftirqd).
>>          */
>> -       I915_WRITE(GEN9_MEDIA_PG_IDLE_HYSTERESIS, 250);
>> -       I915_WRITE(GEN9_RENDER_PG_IDLE_HYSTERESIS, 250);
>> +       I915_WRITE(GEN9_MEDIA_PG_IDLE_HYSTERESIS, 25);
>> +       I915_WRITE(GEN9_RENDER_PG_IDLE_HYSTERESIS, 25);
>
> We were using higher than recommended for the simple reason of not
> allowing it to powergate while signaling between engines. We are much
> faster now (though be sure to disable semaphores to put us in worse
> case) and since we use one value, we need to measure on the slow
> platform.
>
> Anyway, just pointing out there was a reason for a relatively large
> hysteresis.

Then we should just drop this patch. Ta for pointing out the
reasoning.
-Mika