[PATCH v2 1/3] drm/mediatek: Fix YCbCr422 color format issue for DP

[Liankun Yang <liankun.yang@mediatek.com>]

Setting up misc0 for Pixel Encoding Format.

According to the definition of YCbCr in spec 1.2a Table 2-96,
0x1 << 1 should be written to the register.

Use switch case to distinguish RGB, YCbCr422,
and unsupported color formats.

Fixes: f70ac097a2cf ("drm/mediatek: Add MT8195 Embedded DisplayPort driver")
Signed-off-by: Liankun Yang <liankun.yang@mediatek.com>
---
Change in V2
- Modify the value written to the register
Per suggestion from the previous thread:
https://patchwork.kernel.org/project/linux-mediatek/patch/20240510021810.19302-1-liankun.yang@mediatek.com/
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index f0f6f402994a..613e1c842478 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -460,18 +460,16 @@ static int mtk_dp_set_color_format(struct mtk_dp *mtk_dp,
 				   enum dp_pixelformat color_format)
 {
 	u32 val;
-
-	/* update MISC0 */
-	mtk_dp_update_bits(mtk_dp, MTK_DP_ENC0_P0_3034,
-			   color_format << DP_TEST_COLOR_FORMAT_SHIFT,
-			   DP_TEST_COLOR_FORMAT_MASK);
+	u32 misc0_color;
 
 	switch (color_format) {
 	case DP_PIXELFORMAT_YUV422:
 		val = PIXEL_ENCODE_FORMAT_DP_ENC0_P0_YCBCR422;
+		misc0_color = DP_COLOR_FORMAT_YCbCr422;
 		break;
 	case DP_PIXELFORMAT_RGB:
 		val = PIXEL_ENCODE_FORMAT_DP_ENC0_P0_RGB;
+		misc0_color = DP_COLOR_FORMAT_RGB;
 		break;
 	default:
 		drm_warn(mtk_dp->drm_dev, "Unsupported color format: %d\n",
@@ -479,6 +477,11 @@ static int mtk_dp_set_color_format(struct mtk_dp *mtk_dp,
 		return -EINVAL;
 	}
 
+	/* update MISC0 */
+	mtk_dp_update_bits(mtk_dp, MTK_DP_ENC0_P0_3034,
+			   misc0_color,
+			   DP_TEST_COLOR_FORMAT_MASK);
+
 	mtk_dp_update_bits(mtk_dp, MTK_DP_ENC0_P0_303C,
 			   val, PIXEL_ENCODE_FORMAT_DP_ENC0_P0_MASK);
 	return 0;
-- 
2.45.2