Re: [RFC 3/4] drm/i915: valleyview: Make intel_set_rps get FORCEWAKE_MEDIA

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Hi,

On 01-01-17 21:24, Chris Wilson wrote:
On Sun, Jan 01, 2017 at 09:14:02PM +0100, Hans de Goede wrote:
All callers of valleyview_set_rps() get at least FORCEWAKE_MEDIA, except
for intel_set_rps(). Since intel_set_rps can for example be called from
sysfs store functions, there is no guarantee this is already done, so add
an intel_uncore_forcewake_get(FORCEWAKE_MEDIA) call to intel_set_rps.

Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
 drivers/gpu/drm/i915/intel_pm.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 4b12637..cc4fbd7 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -5096,9 +5096,14 @@ void gen6_rps_boost(struct drm_i915_private *dev_priv,

 void intel_set_rps(struct drm_i915_private *dev_priv, u8 val)
 {
-	if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
+	if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv)) {
+		/* Wake up the media well, as that takes a lot less
+		 * power than the Render well.
+		 */
+		intel_uncore_forcewake_get(dev_priv, FORCEWAKE_MEDIA);
 		valleyview_set_rps(dev_priv, val);

Both powerwells are woken for rps. (Taking one but not the other has no
benefit, and very misleading.)

The comment on why FORCEWAKE_MEDIA is used + code is copy pasted from the
existing code in vlv_set_rps_idle().

> The forcewake is already held by the
lower level routines, taking the wakelock in the caller is an optimisation
that is only interesting if there is a danger from the forcewake being
dropped mid-sequence (due to preemption whatever).

We're also accessing the punit in valleyview_set_rps() and I've seen several
patches (in the android x86 kernel) suggesting that we need to take a wakelock
while doing this.

Regards,

Hans
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