drm/ingenic: Properly compute timings when using a 3x8-bit panel

The LCD controller expects timing values in dot-clock ticks, which is 3x
the timing values in pixels when using a 3x8-bit display; but it will
count the display area size in pixels either way. Go figure.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201119155559.14112-3-paul@crapouillou.net

drivers/gpu/drm/ingenic/ingenic-drm-drv.c

@@ -644,6 +644,7 @@ static int ingenic_drm_encoder_atomic_check(struct drm_encoder *encoder,
 					    struct drm_connector_state *conn_state)
 {
 	struct drm_display_info *info = &conn_state->connector->display_info;
+	struct drm_display_mode *mode = &crtc_state->adjusted_mode;
 
 	if (info->num_bus_formats != 1)
 		return -EINVAL;
@@ -652,10 +653,22 @@ static int ingenic_drm_encoder_atomic_check(struct drm_encoder *encoder,
 		return 0;
 
 	switch (*info->bus_formats) {
+	case MEDIA_BUS_FMT_RGB888_3X8:
+		/*
+		 * The LCD controller expects timing values in dot-clock ticks,
+		 * which is 3x the timing values in pixels when using a 3x8-bit
+		 * display; but it will count the display area size in pixels
+		 * either way. Go figure.
+		 */
+		mode->crtc_clock = mode->clock * 3;
+		mode->crtc_hsync_start = mode->hsync_start * 3 - mode->hdisplay * 2;
+		mode->crtc_hsync_end = mode->hsync_end * 3 - mode->hdisplay * 2;
+		mode->crtc_hdisplay = mode->hdisplay;
+		mode->crtc_htotal = mode->htotal * 3 - mode->hdisplay * 2;
+		return 0;
 	case MEDIA_BUS_FMT_RGB565_1X16:
 	case MEDIA_BUS_FMT_RGB666_1X18:
 	case MEDIA_BUS_FMT_RGB888_1X24:
-	case MEDIA_BUS_FMT_RGB888_3X8:
 		return 0;
 	default:
 		return -EINVAL;