drm/bridge: anx7625: Tune K value for IVO panel

IVO panel require less input video clock variation than video clock
variation in DP CTS spec.

This patch decreases the K value of ANX7625 which will shrink eDP Tx
video clock variation to meet IVO panel's requirement.
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Xin Ji <xji@analogixsemi.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210806104407.2208538-1-xji@analogixsemi.com

drivers/gpu/drm/bridge/analogix/anx7625.c

@@ -384,6 +384,25 @@ static int anx7625_odfc_config(struct anx7625_data *ctx,
 	return ret;
 }
 
+/*
+ * The MIPI source video data exist large variation (e.g. 59Hz ~ 61Hz),
+ * anx7625 defined K ratio for matching MIPI input video clock and
+ * DP output video clock. Increase K value can match bigger video data
+ * variation. IVO panel has small variation than DP CTS spec, need
+ * decrease the K value.
+ */
+static int anx7625_set_k_value(struct anx7625_data *ctx)
+{
+	struct edid *edid = (struct edid *)ctx->slimport_edid_p.edid_raw_data;
+
+	if (edid->mfg_id[0] == IVO_MID0 && edid->mfg_id[1] == IVO_MID1)
+		return anx7625_reg_write(ctx, ctx->i2c.rx_p1_client,
+					 MIPI_DIGITAL_ADJ_1, 0x3B);
+
+	return anx7625_reg_write(ctx, ctx->i2c.rx_p1_client,
+				 MIPI_DIGITAL_ADJ_1, 0x3D);
+}
+
 static int anx7625_dsi_video_timing_config(struct anx7625_data *ctx)
 {
 	struct device *dev = &ctx->client->dev;
@@ -470,9 +489,8 @@ static int anx7625_dsi_video_timing_config(struct anx7625_data *ctx)
 			MIPI_PLL_N_NUM_15_8, (n >> 8) & 0xff);
 	ret |= anx7625_reg_write(ctx, ctx->i2c.rx_p1_client, MIPI_PLL_N_NUM_7_0,
 			(n & 0xff));
-	/* Diff */
-	ret |= anx7625_reg_write(ctx, ctx->i2c.rx_p1_client,
-			MIPI_DIGITAL_ADJ_1, 0x3D);
+
+	anx7625_set_k_value(ctx);
 
 	ret |= anx7625_odfc_config(ctx, post_divider - 1);
 

drivers/gpu/drm/bridge/analogix/anx7625.h

@@ -210,7 +210,9 @@
 #define  MIPI_VIDEO_STABLE_CNT           0x0A
 
 #define  MIPI_LANE_CTRL_10               0x0F
-#define  MIPI_DIGITAL_ADJ_1   0x1B
+#define  MIPI_DIGITAL_ADJ_1     0x1B
+#define  IVO_MID0               0x26
+#define  IVO_MID1               0xCF
 
 #define  MIPI_PLL_M_NUM_23_16   0x1E
 #define  MIPI_PLL_M_NUM_15_8    0x1F