drm/i915/gt: Suppress threshold updates on RPS parking

When we park RPS, we set the GPU to run at minimum 'idle' frequency.
However, as the GPU is idle, we also disable the worker and RPS
interrupts - changing the RPS thresholds has no effect, it just incurs
extra changes to restore them when we unpark. So on parking, leave the
thresholds set to the current power level and so we expect them to be
valid for our restart.

References: https://gitlab.freedesktop.org/drm/intel/issues/848Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Andi Shyti <andi.shyti@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191218210545.3975426-2-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_rps.c

@@ -682,7 +682,7 @@ static int vlv_rps_set(struct intel_rps *rps, u8 val)
 	return err;
 }
 
-static int rps_set(struct intel_rps *rps, u8 val)
+static int rps_set(struct intel_rps *rps, u8 val, bool update)
 {
 	struct drm_i915_private *i915 = rps_to_i915(rps);
 	int err;
@@ -700,7 +700,8 @@ static int rps_set(struct intel_rps *rps, u8 val)
 	if (err)
 		return err;
 
-	gen6_rps_set_thresholds(rps, val);
+	if (update)
+		gen6_rps_set_thresholds(rps, val);
 	rps->last_freq = val;
 
 	return 0;
@@ -760,7 +761,7 @@ void intel_rps_park(struct intel_rps *rps)
 	 * power than the render powerwell.
 	 */
 	intel_uncore_forcewake_get(rps_to_uncore(rps), FORCEWAKE_MEDIA);
-	rps_set(rps, rps->idle_freq);
+	rps_set(rps, rps->idle_freq, false);
 	intel_uncore_forcewake_put(rps_to_uncore(rps), FORCEWAKE_MEDIA);
 }
 
@@ -796,7 +797,7 @@ int intel_rps_set(struct intel_rps *rps, u8 val)
 	GEM_BUG_ON(val < rps->min_freq);
 
 	if (rps->active) {
-		err = rps_set(rps, val);
+		err = rps_set(rps, val, true);
 		if (err)
 			return err;
 
@@ -876,7 +877,7 @@ static bool rps_reset(struct intel_rps *rps)
 	rps->power.mode = -1;
 	rps->last_freq = -1;
 
-	if (rps_set(rps, rps->min_freq)) {
+	if (rps_set(rps, rps->min_freq, true)) {
 		DRM_ERROR("Failed to reset RPS to initial values\n");
 		return false;
 	}