drm/ingenic: Add support for serial 8-bit delta-RGB panels

Add support for 24-bit panels that are connected through a 8-bit bus and
use delta-RGB, which means a RGB pixel ordering on odd lines, and a GBR
pixel ordering on even lines.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201119155559.14112-4-paul@crapouillou.net

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

@@ -590,7 +590,7 @@ static void ingenic_drm_encoder_atomic_mode_set(struct drm_encoder *encoder,
 	struct drm_display_mode *mode = &crtc_state->adjusted_mode;
 	struct drm_connector *conn = conn_state->connector;
 	struct drm_display_info *info = &conn->display_info;
-	unsigned int cfg;
+	unsigned int cfg, rgbcfg = 0;
 
 	priv->panel_is_sharp = info->bus_flags & DRM_BUS_FLAG_SHARP_SIGNALS;
 
@@ -627,6 +627,9 @@ static void ingenic_drm_encoder_atomic_mode_set(struct drm_encoder *encoder,
 			case MEDIA_BUS_FMT_RGB888_1X24:
 				cfg |= JZ_LCD_CFG_MODE_GENERIC_24BIT;
 				break;
+			case MEDIA_BUS_FMT_RGB888_3X8_DELTA:
+				rgbcfg = JZ_LCD_RGBC_EVEN_GBR | JZ_LCD_RGBC_ODD_RGB;
+				fallthrough;
 			case MEDIA_BUS_FMT_RGB888_3X8:
 				cfg |= JZ_LCD_CFG_MODE_8BIT_SERIAL;
 				break;
@@ -637,6 +640,7 @@ static void ingenic_drm_encoder_atomic_mode_set(struct drm_encoder *encoder,
 	}
 
 	regmap_write(priv->map, JZ_REG_LCD_CFG, cfg);
+	regmap_write(priv->map, JZ_REG_LCD_RGBC, rgbcfg);
 }
 
 static int ingenic_drm_encoder_atomic_check(struct drm_encoder *encoder,
@@ -654,6 +658,7 @@ static int ingenic_drm_encoder_atomic_check(struct drm_encoder *encoder,
 
 	switch (*info->bus_formats) {
 	case MEDIA_BUS_FMT_RGB888_3X8:
+	case MEDIA_BUS_FMT_RGB888_3X8_DELTA:
 		/*
 		 * The LCD controller expects timing values in dot-clock ticks,
 		 * which is 3x the timing values in pixels when using a 3x8-bit

drivers/gpu/drm/ingenic/ingenic-drm.h

@@ -31,6 +31,7 @@
 #define JZ_REG_LCD_SA1				0x54
 #define JZ_REG_LCD_FID1				0x58
 #define JZ_REG_LCD_CMD1				0x5C
+#define JZ_REG_LCD_RGBC				0x90
 #define JZ_REG_LCD_OSDC				0x100
 #define JZ_REG_LCD_OSDCTRL			0x104
 #define JZ_REG_LCD_OSDS				0x108
@@ -138,6 +139,19 @@
 #define JZ_LCD_STATE_SOF_IRQ			BIT(4)
 #define JZ_LCD_STATE_DISABLED			BIT(0)
 
+#define JZ_LCD_RGBC_ODD_RGB			(0x0 << 4)
+#define JZ_LCD_RGBC_ODD_RBG			(0x1 << 4)
+#define JZ_LCD_RGBC_ODD_GRB			(0x2 << 4)
+#define JZ_LCD_RGBC_ODD_GBR			(0x3 << 4)
+#define JZ_LCD_RGBC_ODD_BRG			(0x4 << 4)
+#define JZ_LCD_RGBC_ODD_BGR			(0x5 << 4)
+#define JZ_LCD_RGBC_EVEN_RGB			(0x0 << 0)
+#define JZ_LCD_RGBC_EVEN_RBG			(0x1 << 0)
+#define JZ_LCD_RGBC_EVEN_GRB			(0x2 << 0)
+#define JZ_LCD_RGBC_EVEN_GBR			(0x3 << 0)
+#define JZ_LCD_RGBC_EVEN_BRG			(0x4 << 0)
+#define JZ_LCD_RGBC_EVEN_BGR			(0x5 << 0)
+
 #define JZ_LCD_OSDC_OSDEN			BIT(0)
 #define JZ_LCD_OSDC_F0EN			BIT(3)
 #define JZ_LCD_OSDC_F1EN			BIT(4)