drm/i915/dsb: Split intel_dsb_wait() from intel_dsb_commit()

Starting the DSB execution vs. waiting for it stop are two
totally different things. Split intel_dsb_wait() from
intel_dsb_commit() so that we can eventually allow the DSB
to execute asynchronously.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230118163040.29808-4-ville.syrjala@linux.intel.comReviewed-by: Animesh Manna <animesh.manna@intel.com>

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

@@ -1256,8 +1256,10 @@ static void icl_load_luts(const struct intel_crtc_state *crtc_state)
 		break;
 	}
 
-	if (crtc_state->dsb)
+	if (crtc_state->dsb) {
 		intel_dsb_commit(crtc_state->dsb);
+		intel_dsb_wait(crtc_state->dsb);
+	}
 }
 
 static u32 chv_cgm_degamma_ldw(const struct drm_color_lut *color)

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

@@ -235,7 +235,7 @@ void intel_dsb_commit(struct intel_dsb *dsb)
 	if (is_dsb_busy(dev_priv, pipe, dsb->id)) {
 		drm_err(&dev_priv->drm, "[CRTC:%d:%s] DSB %d is busy\n",
 			crtc->base.base.id, crtc->base.name, dsb->id);
-		goto reset;
+		return;
 	}
 
 	intel_de_write(dev_priv, DSB_CTRL(pipe, dsb->id),
@@ -249,13 +249,20 @@ void intel_dsb_commit(struct intel_dsb *dsb)
 		    "DSB execution started - head 0x%x, tail 0x%x\n",
 		    i915_ggtt_offset(dsb->vma),
 		    i915_ggtt_offset(dsb->vma) + tail);
+}
+
+void intel_dsb_wait(struct intel_dsb *dsb)
+{
+	struct intel_crtc *crtc = dsb->crtc;
+	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
+	enum pipe pipe = crtc->pipe;
 
 	if (wait_for(!is_dsb_busy(dev_priv, pipe, dsb->id), 1))
 		drm_err(&dev_priv->drm,
 			"[CRTC:%d:%s] DSB %d timed out waiting for idle\n",
 			crtc->base.base.id, crtc->base.name, dsb->id);
 
-reset:
+	/* Attempt to reset it */
 	dsb->free_pos = 0;
 	dsb->ins_start_offset = 0;
 	intel_de_write(dev_priv, DSB_CTRL(pipe, dsb->id), 0);

drivers/gpu/drm/i915/display/intel_dsb.h

@@ -19,5 +19,6 @@ void intel_dsb_cleanup(struct intel_dsb *dsb);
 void intel_dsb_reg_write(struct intel_dsb *dsb,
 			 i915_reg_t reg, u32 val);
 void intel_dsb_commit(struct intel_dsb *dsb);
+void intel_dsb_wait(struct intel_dsb *dsb);
 
 #endif