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Commit c9efef7b authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Update comment in vlv_set_rps_idle() 



Ville explained that the wakelock was being acquired during set-idle in
order to flush the voltage change from the punit.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170102152845.32352-1-chris@chris-wilson.co.uk


Reviewed-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
parent bae3fdce

drivers/gpu/drm/i915/intel_pm.c

+12 −2
Original line number Diff line number Diff line
@@ -5004,8 +5004,18 @@ 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 committing the voltage change) as that takes a lot less

	 * power than the render powerwell.

	 */

	intel_uncore_forcewake_get(dev_priv, FORCEWAKE_MEDIA);

	valleyview_set_rps(dev_priv, val);

	intel_uncore_forcewake_put(dev_priv, FORCEWAKE_MEDIA);