drm/vc4: Expose gamma as atomic property

We are an atomic driver so the gamma LUT should also be exposed as a
CRTC property through the DRM atomic color management. This will also
take care of the legacy path for us.
Signed-off-by: Stefan Schake <stschake@gmail.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/1523479755-20812-3-git-send-email-stschake@gmail.com

drivers/gpu/drm/vc4/vc4_crtc.c

@@ -298,23 +298,21 @@ vc4_crtc_lut_load(struct drm_crtc *crtc)
 		HVS_WRITE(SCALER_GAMDATA, vc4_crtc->lut_b[i]);
 }
 
-static int
-vc4_crtc_gamma_set(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b,
-		   uint32_t size,
-		   struct drm_modeset_acquire_ctx *ctx)
+static void
+vc4_crtc_update_gamma_lut(struct drm_crtc *crtc)
 {
 	struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
+	struct drm_color_lut *lut = crtc->state->gamma_lut->data;
+	u32 length = drm_color_lut_size(crtc->state->gamma_lut);
 	u32 i;
 
-	for (i = 0; i < size; i++) {
-		vc4_crtc->lut_r[i] = r[i] >> 8;
-		vc4_crtc->lut_g[i] = g[i] >> 8;
-		vc4_crtc->lut_b[i] = b[i] >> 8;
+	for (i = 0; i < length; i++) {
+		vc4_crtc->lut_r[i] = drm_color_lut_extract(lut[i].red, 8);
+		vc4_crtc->lut_g[i] = drm_color_lut_extract(lut[i].green, 8);
+		vc4_crtc->lut_b[i] = drm_color_lut_extract(lut[i].blue, 8);
 	}
 
 	vc4_crtc_lut_load(crtc);
-
-	return 0;
 }
 
 static u32 vc4_get_fifo_full_level(u32 format)
@@ -699,6 +697,22 @@ static void vc4_crtc_atomic_flush(struct drm_crtc *crtc,
 	if (crtc->state->active && old_state->active)
 		vc4_crtc_update_dlist(crtc);
 
+	if (crtc->state->color_mgmt_changed) {
+		u32 dispbkgndx = HVS_READ(SCALER_DISPBKGNDX(vc4_crtc->channel));
+
+		if (crtc->state->gamma_lut) {
+			vc4_crtc_update_gamma_lut(crtc);
+			dispbkgndx |= SCALER_DISPBKGND_GAMMA;
+		} else {
+			/* Unsetting DISPBKGND_GAMMA skips the gamma lut step
+			 * in hardware, which is the same as a linear lut that
+			 * DRM expects us to use in absence of a user lut.
+			 */
+			dispbkgndx &= ~SCALER_DISPBKGND_GAMMA;
+		}
+		HVS_WRITE(SCALER_DISPBKGNDX(vc4_crtc->channel), dispbkgndx);
+	}
+
 	if (debug_dump_regs) {
 		DRM_INFO("CRTC %d HVS after:\n", drm_crtc_index(crtc));
 		vc4_hvs_dump_state(dev);
@@ -909,7 +923,7 @@ static const struct drm_crtc_funcs vc4_crtc_funcs = {
 	.reset = vc4_crtc_reset,
 	.atomic_duplicate_state = vc4_crtc_duplicate_state,
 	.atomic_destroy_state = vc4_crtc_destroy_state,
-	.gamma_set = vc4_crtc_gamma_set,
+	.gamma_set = drm_atomic_helper_legacy_gamma_set,
 	.enable_vblank = vc4_enable_vblank,
 	.disable_vblank = vc4_disable_vblank,
 };
@@ -1035,6 +1049,7 @@ static int vc4_crtc_bind(struct device *dev, struct device *master, void *data)
 	primary_plane->crtc = crtc;
 	vc4_crtc->channel = vc4_crtc->data->hvs_channel;
 	drm_mode_crtc_set_gamma_size(crtc, ARRAY_SIZE(vc4_crtc->lut_r));
+	drm_crtc_enable_color_mgmt(crtc, 0, false, crtc->gamma_size);
 
 	/* Set up some arbitrary number of planes.  We're not limited
 	 * by a set number of physical registers, just the space in