drm/vc4: hvs: Store channel in variable

The assigned_channel field of our vc4_crtc_state structure is accessed
multiple times in vc4_hvs_atomic_flush, so let's move it to a variable
that can be used in all those places.
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20220331143744.777652-4-maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_hvs.c

@@ -460,6 +460,7 @@ void vc4_hvs_atomic_flush(struct drm_crtc *crtc,
 	struct drm_device *dev = crtc->dev;
 	struct vc4_dev *vc4 = to_vc4_dev(dev);
 	struct vc4_crtc_state *vc4_state = to_vc4_crtc_state(crtc->state);
+	unsigned int channel = vc4_state->assigned_channel;
 	struct drm_plane *plane;
 	struct vc4_plane_state *vc4_plane_state;
 	bool debug_dump_regs = false;
@@ -500,8 +501,8 @@ void vc4_hvs_atomic_flush(struct drm_crtc *crtc,
 		/* This sets a black background color fill, as is the case
 		 * with other DRM drivers.
 		 */
-		HVS_WRITE(SCALER_DISPBKGNDX(vc4_state->assigned_channel),
-			  HVS_READ(SCALER_DISPBKGNDX(vc4_state->assigned_channel)) |
+		HVS_WRITE(SCALER_DISPBKGNDX(channel),
+			  HVS_READ(SCALER_DISPBKGNDX(channel)) |
 			  SCALER_DISPBKGND_FILL);
 
 	/* Only update DISPLIST if the CRTC was already running and is not
@@ -515,7 +516,7 @@ void vc4_hvs_atomic_flush(struct drm_crtc *crtc,
 		vc4_hvs_update_dlist(crtc);
 
 	if (crtc->state->color_mgmt_changed) {
-		u32 dispbkgndx = HVS_READ(SCALER_DISPBKGNDX(vc4_state->assigned_channel));
+		u32 dispbkgndx = HVS_READ(SCALER_DISPBKGNDX(channel));
 
 		if (crtc->state->gamma_lut) {
 			vc4_hvs_update_gamma_lut(crtc);
@@ -527,7 +528,7 @@ void vc4_hvs_atomic_flush(struct drm_crtc *crtc,
 			 */
 			dispbkgndx &= ~SCALER_DISPBKGND_GAMMA;
 		}
-		HVS_WRITE(SCALER_DISPBKGNDX(vc4_state->assigned_channel), dispbkgndx);
+		HVS_WRITE(SCALER_DISPBKGNDX(channel), dispbkgndx);
 	}
 
 	if (debug_dump_regs) {