drm/bridge: fsl-ldb: Add i.MX6SX support

i.MX6SX has a single LVDS port and share a similar LDB_CTRL register layout
with i.MX8MP and i.MX93.

There is no LVDS CTRL register on the i.MX6SX, so only write to
this register on the appropriate SoCs.

Add support for the i.MX6SX LDB.

Tested on a imx6sx-sdb board with a Hannstar HSD100PXN1 LVDS panel
and also on a custom i.MX6SX-based board.
Signed-off-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Marek Vasut <marex@denx.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230404020129.509356-2-festevam@gmail.com

drivers/gpu/drm/bridge/fsl-ldb.c

@@ -56,6 +56,7 @@
 #define LVDS_CTRL_VBG_ADJ_MASK			GENMASK(19, 17)
 
 enum fsl_ldb_devtype {
+	IMX6SX_LDB,
 	IMX8MP_LDB,
 	IMX93_LDB,
 };
@@ -64,9 +65,14 @@ struct fsl_ldb_devdata {
 	u32 ldb_ctrl;
 	u32 lvds_ctrl;
 	bool lvds_en_bit;
+	bool single_ctrl_reg;
 };
 
 static const struct fsl_ldb_devdata fsl_ldb_devdata[] = {
+	[IMX6SX_LDB] = {
+		.ldb_ctrl = 0x18,
+		.single_ctrl_reg = true,
+	},
 	[IMX8MP_LDB] = {
 		.ldb_ctrl = 0x5c,
 		.lvds_ctrl = 0x128,
@@ -201,6 +207,9 @@ static void fsl_ldb_atomic_enable(struct drm_bridge *bridge,
 
 	regmap_write(fsl_ldb->regmap, fsl_ldb->devdata->ldb_ctrl, reg);
 
+	if (fsl_ldb->devdata->single_ctrl_reg)
+		return;
+
 	/* Program LVDS_CTRL */
 	reg = LVDS_CTRL_CC_ADJ(2) | LVDS_CTRL_PRE_EMPH_EN |
 	      LVDS_CTRL_PRE_EMPH_ADJ(3) | LVDS_CTRL_VBG_EN;
@@ -226,6 +235,7 @@ static void fsl_ldb_atomic_disable(struct drm_bridge *bridge,
 		regmap_write(fsl_ldb->regmap, fsl_ldb->devdata->lvds_ctrl,
 			     LVDS_CTRL_LVDS_EN);
 	else
+		if (!fsl_ldb->devdata->single_ctrl_reg)
 			regmap_write(fsl_ldb->regmap, fsl_ldb->devdata->lvds_ctrl, 0);
 	regmap_write(fsl_ldb->regmap, fsl_ldb->devdata->ldb_ctrl, 0);
 
@@ -372,6 +382,8 @@ static void fsl_ldb_remove(struct platform_device *pdev)
 }
 
 static const struct of_device_id fsl_ldb_match[] = {
+	{ .compatible = "fsl,imx6sx-ldb",
+	  .data = &fsl_ldb_devdata[IMX6SX_LDB], },
 	{ .compatible = "fsl,imx8mp-ldb",
 	  .data = &fsl_ldb_devdata[IMX8MP_LDB], },
 	{ .compatible = "fsl,imx93-ldb",