drm: rcar-du: Add support for LVDS mode selection

Retrieve the LVDS mode from the panel and configure the LVDS encoder
accordingly. LVDS mode selection is static as LVDS panels can't be
hot-plugged on any of the device supported by the driver. Support for
dynamic mode selection can be implemented in the future when needed.

Signed-off-by: Laurent Pinchart <[e-mail]>

drivers/gpu/drm/rcar-du/rcar_du_encoder.c

···
 				     struct drm_connector_state *conn_state)
 {
 	struct rcar_du_encoder *renc = to_rcar_encoder(encoder);
+	struct drm_display_info *info = &conn_state->connector->display_info;
+	enum rcar_lvds_mode mode;
 
 	rcar_du_crtc_route_output(crtc_state->crtc, renc->output);
 
···
 	}
 
 	renc->connector = to_rcar_connector(conn_state->connector);
+
+	if (!info->num_bus_formats || !info->bus_formats) {
+		dev_err(encoder->dev->dev, "no LVDS bus format reported\n");
+		return;
+	}
+
+	switch (info->bus_formats[0]) {
+	case MEDIA_BUS_FMT_RGB666_1X7X3_SPWG:
+	case MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA:
+		mode = RCAR_LVDS_MODE_JEIDA;
+		break;
+	case MEDIA_BUS_FMT_RGB888_1X7X4_SPWG:
+		mode = RCAR_LVDS_MODE_VESA;
+		break;
+	default:
+		dev_err(encoder->dev->dev,
+			"unsupported LVDS bus format 0x%04x\n",
+			info->bus_formats[0]);
+		return;
+	}
+
+	if (info->bus_flags & DRM_BUS_FLAG_DATA_LSB_TO_MSB)
+		mode |= RCAR_LVDS_MODE_MIRROR;
+
+	rcar_du_lvdsenc_set_mode(renc->lvds, mode);
 }
 
 static const struct drm_encoder_helper_funcs encoder_helper_funcs = {

drivers/gpu/drm/rcar-du/rcar_du_lvdsenc.c

···
 	bool enabled;
 
 	enum rcar_lvds_input input;
+	enum rcar_lvds_mode mode;
 };
 
 static void rcar_lvds_write(struct rcar_du_lvdsenc *lvds, u32 reg, u32 data)
···
 	/* Select the input, hardcode mode 0, enable LVDS operation and turn
 	 * bias circuitry on.
 	 */
-	lvdcr0 = LVDCR0_BEN | LVDCR0_LVEN;
+	lvdcr0 = (lvds->mode << LVDCR0_LVMD_SHIFT) | LVDCR0_BEN | LVDCR0_LVEN;
 	if (rcrtc->index == 2)
 		lvdcr0 |= LVDCR0_DUSEL;
 	rcar_lvds_write(lvds, LVDCR0, lvdcr0);
···
 	 * Turn the PLL on, set it to LVDS normal mode, wait for the startup
 	 * delay and turn the output on.
 	 */
-	lvdcr0 = LVDCR0_PLLON;
+	lvdcr0 = (lvds->mode << LVDCR0_LVMD_SHIFT) | LVDCR0_PLLON;
 	rcar_lvds_write(lvds, LVDCR0, lvdcr0);
 
 	lvdcr0 |= LVDCR0_PWD;
···
 		mode->clock = clamp(mode->clock, 30000, 150000);
 	else
 		mode->clock = clamp(mode->clock, 25175, 148500);
+}
+
+void rcar_du_lvdsenc_set_mode(struct rcar_du_lvdsenc *lvds,
+			      enum rcar_lvds_mode mode)
+{
+	lvds->mode = mode;
 }
 
 static int rcar_du_lvdsenc_get_resources(struct rcar_du_lvdsenc *lvds,

drivers/gpu/drm/rcar-du/rcar_du_lvdsenc.h

···
 	RCAR_LVDS_INPUT_DU2,
 };
 
+/* Keep in sync with the LVDCR0.LVMD hardware register values. */
+enum rcar_lvds_mode {
+	RCAR_LVDS_MODE_JEIDA = 0,
+	RCAR_LVDS_MODE_MIRROR = 1,
+	RCAR_LVDS_MODE_VESA = 4,
+};
+
 #if IS_ENABLED(CONFIG_DRM_RCAR_LVDS)
 int rcar_du_lvdsenc_init(struct rcar_du_device *rcdu);
+void rcar_du_lvdsenc_set_mode(struct rcar_du_lvdsenc *lvds,
+			      enum rcar_lvds_mode mode);
 int rcar_du_lvdsenc_enable(struct rcar_du_lvdsenc *lvds,
 			   struct drm_crtc *crtc, bool enable);
 void rcar_du_lvdsenc_atomic_check(struct rcar_du_lvdsenc *lvds,
···
 static inline int rcar_du_lvdsenc_init(struct rcar_du_device *rcdu)
 {
 	return 0;
+}
+static inline void rcar_du_lvdsenc_set_mode(struct rcar_du_lvdsenc *lvds,
+					    enum rcar_lvds_mode mode)
+{
 }
 static inline int rcar_du_lvdsenc_enable(struct rcar_du_lvdsenc *lvds,
 					 struct drm_crtc *crtc, bool enable)