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

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Message-ID: <CAAOTY_-vwFnSOS8gqVvyxJm_0vC8BPUkAhbnkenOxRgt=DBhjQ@mail.gmail.com>
Date: Tue, 30 Dec 2025 15:57:28 +0000
From: Chun-Kuang Hu <chunkuang.hu@...nel.org>
To: Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>
Cc: 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>, 
	kernel@...labora.com, dri-devel@...ts.freedesktop.org, 
	linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] drm/mediatek: mtk_hdmi_ddc_v2: Add transfer abort on
 timeout cases

Hi, Louis:

Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com> 於 2025年12月5日週五 下午2:22寫道：
>
> 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.

Applied to mediatek-drm-fixes [1], thanks.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/log/?h=mediatek-drm-fixes

Regards,
Chun-Kuang.

>
> 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
>