Re: [PATCH v7 01/11] drm/mediatek: dp: Add missing error checks in mtk_dp_parse_capabilities

["CK Hu (胡俊光)" <ck.hu@mediatek.com>]

Hi, Angelo:

On Tue, 2023-07-25 at 09:32 +0200, AngeloGioacchino Del Regno wrote:
> If reading the RX capabilities fails the training pattern will be set
> wrongly: add error checking for drm_dp_read_dpcd_caps() and return if
> anything went wrong with it.
> 
> While at it, also add a less critical error check when writing to
> clear the ESI0 IRQ vector.

Reviewed-by: CK Hu <ck.hu@mediatek.com>

> 
> Fixes: f70ac097a2cf ("drm/mediatek: Add MT8195 Embedded DisplayPort
> driver")
> Signed-off-by: AngeloGioacchino Del Regno <
> angelogioacchino.delregno@collabora.com>
> Tested-by: Chen-Yu Tsai <wenst@chromium.org>
> Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dp.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c
> b/drivers/gpu/drm/mediatek/mtk_dp.c
> index 64eee77452c0..c58b775877a3 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
> @@ -1588,7 +1588,9 @@ static int mtk_dp_parse_capabilities(struct
> mtk_dp *mtk_dp)
>  	u8 val;
>  	ssize_t ret;
>  
> -	drm_dp_read_dpcd_caps(&mtk_dp->aux, mtk_dp->rx_cap);
> +	ret = drm_dp_read_dpcd_caps(&mtk_dp->aux, mtk_dp->rx_cap);
> +	if (ret < 0)
> +		return ret;
>  
>  	if (drm_dp_tps4_supported(mtk_dp->rx_cap))
>  		mtk_dp->train_info.channel_eq_pattern =
> DP_TRAINING_PATTERN_4;
> @@ -1615,10 +1617,13 @@ static int mtk_dp_parse_capabilities(struct
> mtk_dp *mtk_dp)
>  			return ret == 0 ? -EIO : ret;
>  		}
>  
> -		if (val)
> -			drm_dp_dpcd_writeb(&mtk_dp->aux,
> -					   DP_DEVICE_SERVICE_IRQ_VECTOR
> _ESI0,
> -					   val);
> +		if (val) {
> +			ret = drm_dp_dpcd_writeb(&mtk_dp->aux,
> +						 DP_DEVICE_SERVICE_IRQ_
> VECTOR_ESI0,
> +						 val);
> +			if (ret < 0)
> +				return ret;
> +		}
>  	}
>  
>  	return 0;