drm/i915: Allow cdclk squasher to be reconfigured live

Supposedly we should be able to change the cdclk squasher waveform
even when many pipes are active. Make it so.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211119131348.725220-6-mika.kahola@intel.com

drivers/gpu/drm/i915/display/intel_cdclk.c

@@ -1951,6 +1951,25 @@ static bool intel_cdclk_can_crawl(struct drm_i915_private *dev_priv,
 		a->ref == b->ref;
 }
 
+static bool intel_cdclk_can_squash(struct drm_i915_private *dev_priv,
+				   const struct intel_cdclk_config *a,
+				   const struct intel_cdclk_config *b)
+{
+	/*
+	 * FIXME should store a bit more state in intel_cdclk_config
+	 * to differentiate squasher vs. cd2x divider properly. For
+	 * the moment all platforms with squasher use a fixed cd2x
+	 * divider.
+	 */
+	if (!has_cdclk_squasher(dev_priv))
+		return false;
+
+	return a->cdclk != b->cdclk &&
+		a->vco != 0 &&
+		a->vco == b->vco &&
+		a->ref == b->ref;
+}
+
 /**
  * intel_cdclk_needs_modeset - Determine if changong between the CDCLK
  *                             configurations requires a modeset on all pipes
@@ -1988,7 +2007,17 @@ static bool intel_cdclk_can_cd2x_update(struct drm_i915_private *dev_priv,
 	if (DISPLAY_VER(dev_priv) < 10 && !IS_BROXTON(dev_priv))
 		return false;
 
+	/*
+	 * FIXME should store a bit more state in intel_cdclk_config
+	 * to differentiate squasher vs. cd2x divider properly. For
+	 * the moment all platforms with squasher use a fixed cd2x
+	 * divider.
+	 */
+	if (has_cdclk_squasher(dev_priv))
+		return false;
+
 	return a->cdclk != b->cdclk &&
+		a->vco != 0 &&
 		a->vco == b->vco &&
 		a->ref == b->ref;
 }
@@ -2672,7 +2701,12 @@ int intel_modeset_calc_cdclk(struct intel_atomic_state *state)
 			pipe = INVALID_PIPE;
 	}
 
-	if (intel_cdclk_can_crawl(dev_priv,
+	if (intel_cdclk_can_squash(dev_priv,
+				   &old_cdclk_state->actual,
+				   &new_cdclk_state->actual)) {
+		drm_dbg_kms(&dev_priv->drm,
+			    "Can change cdclk via squasher\n");
+	} else if (intel_cdclk_can_crawl(dev_priv,
 					 &old_cdclk_state->actual,
 					 &new_cdclk_state->actual)) {
 		drm_dbg_kms(&dev_priv->drm,