drm/i915: Skip modeset for cdclk changes if possible

If we have only a single active pipe and the cdclk change only requires
the cd2x divider to be updated bxt+ can do the update with forcing a full
modeset on the pipe. Try to hook that up.

v2:
- Wait for vblank after an optimized CDCLK change.
- Avoid optimization if the pipe needs a modeset (or was disabled).
- Split CDCLK change to a pre/post plane update step.
v3:
- Use correct version of CDCLK state as old state. (Ville)
- Remove unused intel_cdclk_can_skip_modeset()
v4:
- For consistency call intel_set_cdclk_post_plane_update() only during
  modesets (and not fastsets).
v5:
- Remove the logic to update the CD2X divider on-the-fly on ICL, since
  only a divider of 1 is supported there. Clint also noticed that the
  pipe select bits in CDCLK_CTL are oddly defined on ICL, it's not clear
  yet whether that's only an error in the specification.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Abhay Kumar <abhay.kumar@intel.com>
Tested-by: Abhay Kumar <abhay.kumar@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Clint Taylor <Clinton.A.Taylor@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190327101321.3095-1-imre.deak@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -282,7 +282,8 @@ struct drm_i915_display_funcs {
 	void (*get_cdclk)(struct drm_i915_private *dev_priv,
 			  struct intel_cdclk_state *cdclk_state);
 	void (*set_cdclk)(struct drm_i915_private *dev_priv,
-			  const struct intel_cdclk_state *cdclk_state);
+			  const struct intel_cdclk_state *cdclk_state,
+			  enum pipe pipe);
 	int (*get_fifo_size)(struct drm_i915_private *dev_priv,
 			     enum i9xx_plane_id i9xx_plane);
 	int (*compute_pipe_wm)(struct intel_crtc_state *cstate);

drivers/gpu/drm/i915/intel_display.c

@@ -13002,6 +13002,7 @@ static int intel_modeset_checks(struct drm_atomic_state *state)
 	intel_state->active_crtcs = dev_priv->active_crtcs;
 	intel_state->cdclk.logical = dev_priv->cdclk.logical;
 	intel_state->cdclk.actual = dev_priv->cdclk.actual;
+	intel_state->cdclk.pipe = INVALID_PIPE;
 
 	for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state, new_crtc_state, i) {
 		if (new_crtc_state->active)
@@ -13021,6 +13022,8 @@ static int intel_modeset_checks(struct drm_atomic_state *state)
 	 * adjusted_mode bits in the crtc directly.
 	 */
 	if (dev_priv->display.modeset_calc_cdclk) {
+		enum pipe pipe;
+
 		ret = dev_priv->display.modeset_calc_cdclk(state);
 		if (ret < 0)
 			return ret;
@@ -13037,12 +13040,36 @@ static int intel_modeset_checks(struct drm_atomic_state *state)
 				return ret;
 		}
 
+		if (is_power_of_2(intel_state->active_crtcs)) {
+			struct drm_crtc *crtc;
+			struct drm_crtc_state *crtc_state;
+
+			pipe = ilog2(intel_state->active_crtcs);
+			crtc = &intel_get_crtc_for_pipe(dev_priv, pipe)->base;
+			crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
+			if (crtc_state && needs_modeset(crtc_state))
+				pipe = INVALID_PIPE;
+		} else {
+			pipe = INVALID_PIPE;
+		}
+
 		/* All pipes must be switched off while we change the cdclk. */
-		if (intel_cdclk_needs_modeset(&dev_priv->cdclk.actual,
-					      &intel_state->cdclk.actual)) {
+		if (pipe != INVALID_PIPE &&
+		    intel_cdclk_needs_cd2x_update(dev_priv,
+						  &dev_priv->cdclk.actual,
+						  &intel_state->cdclk.actual)) {
+			ret = intel_lock_all_pipes(state);
+			if (ret < 0)
+				return ret;
+
+			intel_state->cdclk.pipe = pipe;
+		} else if (intel_cdclk_needs_modeset(&dev_priv->cdclk.actual,
+						     &intel_state->cdclk.actual)) {
 			ret = intel_modeset_all_pipes(state);
 			if (ret < 0)
 				return ret;
+
+			intel_state->cdclk.pipe = INVALID_PIPE;
 		}
 
 		DRM_DEBUG_KMS("New cdclk calculated to be logical %u kHz, actual %u kHz\n",
@@ -13451,7 +13478,10 @@ static void intel_atomic_commit_tail(struct drm_atomic_state *state)
 	if (intel_state->modeset) {
 		drm_atomic_helper_update_legacy_modeset_state(state->dev, state);
 
-		intel_set_cdclk(dev_priv, &dev_priv->cdclk.actual);
+		intel_set_cdclk_pre_plane_update(dev_priv,
+						 &intel_state->cdclk.actual,
+						 &dev_priv->cdclk.actual,
+						 intel_state->cdclk.pipe);
 
 		/*
 		 * SKL workaround: bspec recommends we disable the SAGV when we
@@ -13480,6 +13510,12 @@ static void intel_atomic_commit_tail(struct drm_atomic_state *state)
 	/* Now enable the clocks, plane, pipe, and connectors that we set up. */
 	dev_priv->display.update_crtcs(state);
 
+	if (intel_state->modeset)
+		intel_set_cdclk_post_plane_update(dev_priv,
+						  &intel_state->cdclk.actual,
+						  &dev_priv->cdclk.actual,
+						  intel_state->cdclk.pipe);
+
 	/* FIXME: We should call drm_atomic_helper_commit_hw_done() here
 	 * already, but still need the state for the delayed optimization. To
 	 * fix this:

drivers/gpu/drm/i915/intel_drv.h

@@ -559,6 +559,8 @@ struct intel_atomic_state {
 
 		int force_min_cdclk;
 		bool force_min_cdclk_changed;
+		/* pipe to which cd2x update is synchronized */
+		enum pipe pipe;
 	} cdclk;
 
 	bool dpll_set, modeset;
@@ -1694,13 +1696,24 @@ void intel_init_cdclk_hooks(struct drm_i915_private *dev_priv);
 void intel_update_max_cdclk(struct drm_i915_private *dev_priv);
 void intel_update_cdclk(struct drm_i915_private *dev_priv);
 void intel_update_rawclk(struct drm_i915_private *dev_priv);
+bool intel_cdclk_needs_cd2x_update(struct drm_i915_private *dev_priv,
+				   const struct intel_cdclk_state *a,
+				   const struct intel_cdclk_state *b);
 bool intel_cdclk_needs_modeset(const struct intel_cdclk_state *a,
 			       const struct intel_cdclk_state *b);
 bool intel_cdclk_changed(const struct intel_cdclk_state *a,
 			 const struct intel_cdclk_state *b);
 void intel_cdclk_swap_state(struct intel_atomic_state *state);
-void intel_set_cdclk(struct drm_i915_private *dev_priv,
-		     const struct intel_cdclk_state *cdclk_state);
+void
+intel_set_cdclk_pre_plane_update(struct drm_i915_private *dev_priv,
+				 const struct intel_cdclk_state *old_state,
+				 const struct intel_cdclk_state *new_state,
+				 enum pipe pipe);
+void
+intel_set_cdclk_post_plane_update(struct drm_i915_private *dev_priv,
+				  const struct intel_cdclk_state *old_state,
+				  const struct intel_cdclk_state *new_state,
+				  enum pipe pipe);
 void intel_dump_cdclk_state(const struct intel_cdclk_state *cdclk_state,
 			    const char *context);