drm/mediatek: add the mipitx driving control

Add a property in device tree to control the driving by different
board.
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Jitao Shi <jitao.shi@mediatek.com>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

drivers/gpu/drm/mediatek/mtk_mipi_tx.c

@@ -125,6 +125,20 @@ static int mtk_mipi_tx_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	ret = of_property_read_u32(dev->of_node, "drive-strength-microamp",
+				   &mipi_tx->mipitx_drive);
+	/* If can't get the "mipi_tx->mipitx_drive", set it default 0x8 */
+	if (ret < 0)
+		mipi_tx->mipitx_drive = 4600;
+
+	/* check the mipitx_drive valid */
+	if (mipi_tx->mipitx_drive > 6000 || mipi_tx->mipitx_drive < 3000) {
+		dev_warn(dev, "drive-strength-microamp is invalid %d, not in 3000 ~ 6000\n",
+			 mipi_tx->mipitx_drive);
+		mipi_tx->mipitx_drive = clamp_val(mipi_tx->mipitx_drive, 3000,
+						  6000);
+	}
+
 	ref_clk_name = __clk_get_name(ref_clk);
 
 	ret = of_property_read_string(dev->of_node, "clock-output-names",

drivers/gpu/drm/mediatek/mtk_mipi_tx.h

@@ -27,6 +27,7 @@ struct mtk_mipi_tx {
 	struct device *dev;
 	void __iomem *regs;
 	u32 data_rate;
+	u32 mipitx_drive;
 	const struct mtk_mipitx_data *driver_data;
 	struct clk_hw pll_hw;
 	struct clk *pll;

drivers/gpu/drm/mediatek/mtk_mt8183_mipi_tx.c

@@ -17,6 +17,9 @@
 #define RG_DSI_BG_CORE_EN		BIT(7)
 #define RG_DSI_PAD_TIEL_SEL		BIT(8)
 
+#define MIPITX_VOLTAGE_SEL	0x0010
+#define RG_DSI_HSTX_LDO_REF_SEL		(0xf << 6)
+
 #define MIPITX_PLL_PWR		0x0028
 #define MIPITX_PLL_CON0		0x002c
 #define MIPITX_PLL_CON1		0x0030
@@ -123,6 +126,10 @@ static void mtk_mipi_tx_power_on_signal(struct phy *phy)
 	mtk_mipi_tx_clear_bits(mipi_tx, MIPITX_D3_SW_CTL_EN, DSI_SW_CTL_EN);
 	mtk_mipi_tx_clear_bits(mipi_tx, MIPITX_CK_SW_CTL_EN, DSI_SW_CTL_EN);
 
+	mtk_mipi_tx_update_bits(mipi_tx, MIPITX_VOLTAGE_SEL,
+				RG_DSI_HSTX_LDO_REF_SEL,
+				(mipi_tx->mipitx_drive - 3000) / 200 << 6);
+
 	mtk_mipi_tx_set_bits(mipi_tx, MIPITX_CK_CKMODE_EN, DSI_CK_CKMODE_EN);
 }