[Intel-gfx] [PATCH] drm/i915/gt: Always take fw around RPS frequency changes

[Chris Wilson]

In the selftest, we are observing that requests to change frequency are
simply not occuring [within a 20ms period]. The assumption was that with
an active GPU, these writes would be flush naturally; this appears to be
false.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_rps.c | 33 ++++++++++++++---------------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_rps.c b/drivers/gpu/drm/i915/gt/intel_rps.c
index 4dcfae16a7ce..3c68358040dd 100644
--- a/drivers/gpu/drm/i915/gt/intel_rps.c
+++ b/drivers/gpu/drm/i915/gt/intel_rps.c
@@ -698,18 +698,32 @@ static int rps_set(struct intel_rps *rps, u8 val, bool update)
 	if (val == rps->last_freq)
 		return 0;
 
+	/*
+	 * 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.
+	 */
+	intel_uncore_forcewake_get(rps_to_uncore(rps), FORCEWAKE_ALL);
+
 	if (IS_VALLEYVIEW(i915) || IS_CHERRYVIEW(i915))
 		err = vlv_rps_set(rps, val);
 	else
 		err = gen6_rps_set(rps, val);
 	if (err)
-		return err;
+		goto out_fw;
 
 	if (update)
 		gen6_rps_set_thresholds(rps, val);
+
 	rps->last_freq = val;
 
-	return 0;
+out_fw:
+	intel_uncore_forcewake_put(rps_to_uncore(rps), FORCEWAKE_ALL);
+	return err;
 }
 
 void intel_rps_unpark(struct intel_rps *rps)
@@ -755,22 +769,7 @@ void intel_rps_park(struct intel_rps *rps)
 	if (rps->last_freq <= rps->idle_freq)
 		return;
 
-	/*
-	 * 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(rps_to_uncore(rps), FORCEWAKE_MEDIA);
 	rps_set(rps, rps->idle_freq, false);
-	intel_uncore_forcewake_put(rps_to_uncore(rps), FORCEWAKE_MEDIA);
 
 	/*
 	 * Since we will try and restart from the previously requested
-- 
2.20.1