linux-kernel - [PATCH 1/2] drm/mediatek: mtk_hdmi_ddc_v2: Add transfer abort on timeout cases

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Message-Id: <20251205-mtk-hdmi-ddc-v2-fixes-v1-1-260dd0d320f4@collabora.com>
Date: Fri, 05 Dec 2025 15:22:26 +0100
From: Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>
To: Chun-Kuang Hu <chunkuang.hu@...nel.org>, 
 Philipp Zabel <p.zabel@...gutronix.de>, David Airlie <airlied@...il.com>, 
 Simona Vetter <simona@...ll.ch>, Matthias Brugger <matthias.bgg@...il.com>, 
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
 CK Hu <ck.hu@...iatek.com>
Cc: kernel@...labora.com, dri-devel@...ts.freedesktop.org, 
 linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, 
 Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>
Subject: [PATCH 1/2] drm/mediatek: mtk_hdmi_ddc_v2: Add transfer abort on
 timeout cases

During a read or write transfer, the mtk_hdmi_ddc_v2 driver polls the
DDC_I2C_IN_PROG bit of HPD_DDC_STATUS register to check if the transfer
completes but do no particular action if a timeout is reached. It could
lead the next transfer attempts to fail because the faulty transfer was
not aborted. So, add in both low level read and write functions a abort
action by writing the DDC_CTRL register with the ABORT_XFER command
value.

Fixes: 8d0f79886273 ("drm/mediatek: Introduce HDMI/DDC v2 for MT8195/MT8188")
Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>
---
 drivers/gpu/drm/mediatek/mtk_hdmi_ddc_v2.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi_ddc_v2.c b/drivers/gpu/drm/mediatek/mtk_hdmi_ddc_v2.c
index b844e2c10f28060baef64bd36c5464758b08e162..6ae7cbba8cb6dacf46c2f7ab74a2d7446d698b69 100644
--- a/drivers/gpu/drm/mediatek/mtk_hdmi_ddc_v2.c
+++ b/drivers/gpu/drm/mediatek/mtk_hdmi_ddc_v2.c
@@ -96,6 +96,11 @@ static int mtk_ddc_wr_one(struct mtk_hdmi_ddc *ddc, u16 addr_id,
 				       !(val & DDC_I2C_IN_PROG), 500, 1000);
 	if (ret) {
 		dev_err(ddc->dev, "DDC I2C write timeout\n");
+
+		/* Abort transfer if it is still in progress */
+		regmap_update_bits(ddc->regs, DDC_CTRL, DDC_CTRL_CMD,
+				   FIELD_PREP(DDC_CTRL_CMD, DDC_CMD_ABORT_XFER));
+
 		return ret;
 	}
 
@@ -179,6 +184,11 @@ static int mtk_ddcm_read_hdmi(struct mtk_hdmi_ddc *ddc, u16 uc_dev,
 					       500 * (temp_length + 5));
 		if (ret) {
 			dev_err(ddc->dev, "Timeout waiting for DDC I2C\n");
+
+			/* Abort transfer if it is still in progress */
+			regmap_update_bits(ddc->regs, DDC_CTRL, DDC_CTRL_CMD,
+					   FIELD_PREP(DDC_CTRL_CMD, DDC_CMD_ABORT_XFER));
+
 			return ret;
 		}
 

-- 
2.52.0