[Intel-gfx] [PATCH] drm/i915: Update comment in vlv_set_rps_idle()

[Chris Wilson]

On Mon, Jan 02, 2017 at 05:56:51PM +0200, Ville Syrjälä wrote:
> On Mon, Jan 02, 2017 at 03:28:45PM +0000, Chris Wilson wrote:
> > Ville explained that the wakelock was being acquired during set-idle in
> > order to flush the voltage change from the punit.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com
> > ---
> >  drivers/gpu/drm/i915/intel_pm.c | 14 ++++++++++++--
> >  1 file changed, 12 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index 4406359c5f81..4c9a1b12dfee 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -5011,8 +5011,18 @@ static void vlv_set_rps_idle(struct drm_i915_private *dev_priv)
> >  	if (dev_priv->rps.cur_freq <= val)
> >  		return;
> >  
> > -	/* Wake up the media well, as that takes a lot less
> > -	 * power than the Render well. */
> > +	/* The punit delays the write of the frequency and voltage until it
> > +	 * determines the GPU is awake. During normal usage we don't want to
> > +	 * waste power changing the frequency if the GPU is sleeping (rc6).
> > +	 * However, the GPU and driver is now idle and we do not want to delay
> > +	 * switching to minimum voltage (reducing power whilst idle) as we do
> > +	 * not expect to be woken in the near future and so must flush the
> > +	 * change by waking the device.
> > +	 *
> > +	 * We choose to take the media powerwell (either would do to trick the
> > +	 * punit into commiting the voltage change) as that takes a lot less
> > +	 * power than the render powerwell.
> > +	 */
> 
> lgtm
> 
> Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Ta, fixed a spelling mistake and pushed.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre