[PATCH v2 1/2] Add write DP phyd register from parse dts

[Liankun Yang]

During the testing phase, screen flickering is observed when
using displayport for screen casting. Relevant SSC register parameters
are set in dts to address the screen flickering issue effectively and
improve compatibility with different devices by adjusting the SSC gear.

Obtaining the DPTX node, parsing the dts to obtain PHY register address
and value can adapt to settings of different manufacturers projects.

Changeds in v2:
- Optimized method of writing to DP PHY register
https://patchwork.kernel.org/project/linux-mediatek/patch/
20240403040517.3279-1-liankun.yang at mediatek.com/

Signed-off-by: Liankun Yang <liankun.yang at mediatek.com>
---
 drivers/phy/mediatek/phy-mtk-dp.c | 37 +++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/drivers/phy/mediatek/phy-mtk-dp.c b/drivers/phy/mediatek/phy-mtk-dp.c
index d7024a144335..ce78112d5938 100644
--- a/drivers/phy/mediatek/phy-mtk-dp.c
+++ b/drivers/phy/mediatek/phy-mtk-dp.c
@@ -28,6 +28,10 @@
 #define MTK_DP_PHY_DIG_SW_RST		(PHY_OFFSET + 0x38)
 #define DP_GLB_SW_RST_PHYD		BIT(0)
 
+#define MTK_DP_PHY_DIG_GLB_DA_REG_14	(PHY_OFFSET + 0xD8)
+#define XTP_GLB_TXPLL_SSC_DELTA_RBR_DEFAULT	GENMASK(15, 0)
+#define XTP_GLB_TXPLL_SSC_DELTA_HBR_DEFAULT	GENMASK(31, 16)
+
 #define MTK_DP_LANE0_DRIVING_PARAM_3		(PHY_OFFSET + 0x138)
 #define MTK_DP_LANE1_DRIVING_PARAM_3		(PHY_OFFSET + 0x238)
 #define MTK_DP_LANE2_DRIVING_PARAM_3		(PHY_OFFSET + 0x338)
@@ -78,10 +82,39 @@
 #define DRIVING_PARAM_8_DEFAULT	(XTP_LN_TX_LCTXCP1_SW2_PRE1_DEFAULT | \
 				 XTP_LN_TX_LCTXCP1_SW3_PRE0_DEFAULT)
 
+#define SSC_SETTING	"dp-ssc-setting"
+#define RG_XTP_GLB_TXPLL_SSC_DELTA_HBR	"ssc-delta-hbr"
+
 struct mtk_dp_phy {
 	struct regmap *regs;
+	struct device *dev;
 };
 
+static int mtk_dp_set_ssc_config(struct phy *phy, struct mtk_dp_phy *dp_phy)
+{
+	int ret;
+	u32 read_value = 0, reg_mask = 0;
+	struct device_node *ssc_node = NULL;
+
+	ssc_node = of_find_node_by_name(dp_phy->dev->of_node, SSC_SETTING);
+	if (!ssc_node) {
+		dev_err(&phy->dev, "SSC node is NULL\n");
+		return -ENODEV;
+	}
+
+	ret = of_property_read_u32(ssc_node, RG_XTP_GLB_TXPLL_SSC_DELTA_HBR, &read_value);
+	if (ret < 0 || !read_value) {
+		dev_err(&phy->dev, "Read SSC vlaue fail!\n");
+		return -EINVAL;
+	}
+	read_value |= read_value << 16;
+	reg_mask |= XTP_GLB_TXPLL_SSC_DELTA_HBR_DEFAULT;
+
+	regmap_update_bits(dp_phy->regs, MTK_DP_PHY_DIG_GLB_DA_REG_14, reg_mask, read_value);
+
+	return 0;
+}
+
 static int mtk_dp_phy_init(struct phy *phy)
 {
 	struct mtk_dp_phy *dp_phy = phy_get_drvdata(phy);
@@ -137,6 +170,8 @@ static int mtk_dp_phy_configure(struct phy *phy, union phy_configure_opts *opts)
 	regmap_update_bits(dp_phy->regs, MTK_DP_PHY_DIG_PLL_CTL_1,
 			   TPLL_SSC_EN, opts->dp.ssc ? TPLL_SSC_EN : 0);
 
+	mtk_dp_set_ssc_config(phy, dp_phy);
+
 	return 0;
 }
 
@@ -186,6 +221,8 @@ static int mtk_dp_phy_probe(struct platform_device *pdev)
 	if (!dev->of_node)
 		phy_create_lookup(phy, "dp", dev_name(dev));
 
+	dp_phy->dev = dev;
+
 	return 0;
 }
 
-- 
2.18.0