[PATCH 7/7] drm/i915: Stop RPS as we adjust thresholds

[Chris Wilson]

Disable RPS by setting RP_CONTROL to 0, remembering its earlier value.
Then adjust the thresholds before re-enabling RP_CONTROL.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_pm.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index d37e95b3525d..e5cfa0377367 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4804,6 +4804,7 @@ static void gen6_set_rps_thresholds(struct drm_i915_private *dev_priv, u8 val)
 	int new_power;
 	u32 threshold_up = 0, threshold_down = 0; /* in % */
 	u32 ei_up = 0, ei_down = 0;
+	u32 rp_control;
 
 	new_power = dev_priv->rps.power;
 	switch (dev_priv->rps.power) {
@@ -4872,6 +4873,12 @@ static void gen6_set_rps_thresholds(struct drm_i915_private *dev_priv, u8 val)
 	spin_lock_irq(&dev_priv->uncore.lock);
 	intel_uncore_forcewake_get__locked(dev_priv, FORCEWAKE_ALL);
 
+	/* Stop RPS before changing thresholds */
+	rp_control = I915_READ_FW(GEN6_RP_CONTROL);
+	I915_WRITE_FW(GEN6_RP_CONTROL, 0);
+	POSTING_READ_FW(GEN6_RP_CONTROL);
+
+	/* Update thresholds and evaluation intervals */
 	I915_WRITE_FW(GEN6_RP_UP_EI,
 		      GT_INTERVAL_FROM_US(dev_priv, ei_up));
 	I915_WRITE_FW(GEN6_RP_UP_THRESHOLD,
@@ -4885,8 +4892,7 @@ static void gen6_set_rps_thresholds(struct drm_i915_private *dev_priv, u8 val)
 					  ei_down * threshold_down / 100));
 
 	/* Restart RPS to reload the thresholds */
-	I915_WRITE_FW(GEN6_RP_CONTROL,
-		      I915_READ_FW(GEN6_RP_CONTROL) | GEN6_RP_ENABLE);
+	I915_WRITE_FW(GEN6_RP_CONTROL, rp_control | GEN6_RP_ENABLE);
 
 	intel_uncore_forcewake_put__locked(dev_priv, FORCEWAKE_ALL);
 	spin_unlock_irq(&dev_priv->uncore.lock);
-- 
2.11.0