[PATCH v4 1/1] drm/mediatek: dp: Add sdp path reset

[Liankun Yang]

When using type-c to type-c to connect to the monitor,
the sound plays normally. If you unplug the type-c and
connect the type-c to hdmi dongle to the monitor, there will be noise.

By capturing the audio data, it is found that
the data position is messy, and there is no error in the data.

Through experiments, it can be restored by resetting the SDP path
when unplugging it.

Signed-off-by: Liankun Yang <liankun.yang@xxxxxxxxxxxx>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
---
Changes in V4:
- Fix align to the right of '('.
Per suggestion from the previous thread:
https://patchwork.kernel.org/project/linux-mediatek/patch/20240925064854.23065-1-liankun.yang@xxxxxxxxxxxx/

Changes in V3:
- No change.
Per suggestion from the previous thread:
https://patchwork.kernel.org/project/linux-mediatek/patch/20240923132521.22785-1-liankun.yang@xxxxxxxxxxxx/

Changes in V2:
- Fix build error.
Per suggestion from the previous thread:
https://patchwork.kernel.org/project/linux-mediatek/patch/20240923133610.23728-1-liankun.yang@xxxxxxxxxxxx/
---
 drivers/gpu/drm/mediatek/mtk_dp.c     | 15 +++++++++++++++
 drivers/gpu/drm/mediatek/mtk_dp_reg.h |  1 +
 2 files changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index 1cc916b16471..4f4233bd83f7 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -1135,6 +1135,18 @@ static void mtk_dp_digital_sw_reset(struct mtk_dp *mtk_dp)
 			   0, DP_TX_TRANSMITTER_4P_RESET_SW_DP_TRANS_P0);
 }
 
+static void mtk_dp_sdp_path_reset(struct mtk_dp *mtk_dp)
+{
+	mtk_dp_update_bits(mtk_dp, MTK_DP_ENC0_P0_3004,
+			   SDP_RESET_SW_DP_ENC0_P0,
+			   SDP_RESET_SW_DP_ENC0_P0);
+
+	/* Wait for sdp path reset to complete */
+	usleep_range(1000, 5000);
+	mtk_dp_update_bits(mtk_dp, MTK_DP_ENC0_P0_3004,
+			   0, SDP_RESET_SW_DP_ENC0_P0);
+}
+
 static void mtk_dp_set_lanes(struct mtk_dp *mtk_dp, int lanes)
 {
 	mtk_dp_update_bits(mtk_dp, MTK_DP_TRANS_P0_35F0,
@@ -2397,6 +2409,9 @@ static void mtk_dp_bridge_atomic_disable(struct drm_bridge *bridge,
 			   DP_PWR_STATE_BANDGAP_TPLL,
 			   DP_PWR_STATE_MASK);
 
+	/* SDP path reset sw*/
+	mtk_dp_sdp_path_reset(mtk_dp);
+
 	/* Ensure the sink is muted */
 	msleep(20);
 }
diff --git a/drivers/gpu/drm/mediatek/mtk_dp_reg.h b/drivers/gpu/drm/mediatek/mtk_dp_reg.h
index 709b79480693..8ad7a9cc259e 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp_reg.h
+++ b/drivers/gpu/drm/mediatek/mtk_dp_reg.h
@@ -86,6 +86,7 @@
 #define MTK_DP_ENC0_P0_3004			0x3004
 #define VIDEO_M_CODE_SEL_DP_ENC0_P0_MASK		BIT(8)
 #define DP_TX_ENCODER_4P_RESET_SW_DP_ENC0_P0		BIT(9)
+#define SDP_RESET_SW_DP_ENC0_P0				BIT(13)
 #define MTK_DP_ENC0_P0_3010			0x3010
 #define HTOTAL_SW_DP_ENC0_P0_MASK			GENMASK(15, 0)
 #define MTK_DP_ENC0_P0_3014			0x3014
-- 
2.45.2