linux-kernel - Re: [PATCH v9 21/22] drm/mediatek: change the aux retries times when receiving AUX

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Date:   Mon, 28 Mar 2022 09:46:06 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     Guillaume Ranquet <granquet@...libre.com>, <airlied@...ux.ie>,
        <angelogioacchino.delregno@...labora.com>,
        <chunfeng.yun@...iatek.com>, <chunkuang.hu@...nel.org>,
        <ck.hu@...iatek.com>, <daniel@...ll.ch>, <deller@....de>,
        <jitao.shi@...iatek.com>, <kishon@...com>, <krzk+dt@...nel.org>,
        <maarten.lankhorst@...ux.intel.com>, <matthias.bgg@...il.com>,
        <mripard@...nel.org>, <p.zabel@...gutronix.de>,
        <robh+dt@...nel.org>, <tzimmermann@...e.de>, <vkoul@...nel.org>
CC:     <devicetree@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-fbdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-phy@...ts.infradead.org>, <markyacoub@...gle.com>
Subject: Re: [PATCH v9 21/22] drm/mediatek: change the aux retries times
 when receiving AUX_DEFER

On Mon, 2022-03-28 at 00:39 +0200, Guillaume Ranquet wrote:
> From: Jitao Shi <jitao.shi@...iatek.com>
> 
> DP 1.4a Section 2.8.7.1.5.6.1:
> A DP Source device shall retry at least seven times upon receiving
> AUX_DEFER before giving up the AUX transaction.
> 
> Aux should retry to send msg whether how many bytes.
> 
> Signed-off-by: Jitao Shi <jitao.shi@...iatek.com>
> Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dp.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c
> b/drivers/gpu/drm/mediatek/mtk_dp.c
> index e099491cc6a4..7a197c4a7143 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
> @@ -2016,7 +2016,7 @@ static ssize_t mtk_dp_aux_transfer(struct
> drm_dp_aux *mtk_aux,
>  	bool is_read;
>  	u8 request;
>  	size_t accessed_bytes = 0;
> -	int retry = 3, ret = 0;
> +	int retry, ret = 0;
>  
>  	mtk_dp = container_of(mtk_aux, struct mtk_dp, aux);
>  
> @@ -2050,14 +2050,21 @@ static ssize_t mtk_dp_aux_transfer(struct
> drm_dp_aux *mtk_aux,
>  	}
>  
>  	if (msg->size == 0) {
> -		ret = mtk_dp_aux_do_transfer(mtk_dp, is_read, request,
> -					     msg->address +
> accessed_bytes,
> -					     msg->buffer +
> accessed_bytes, 0);
> +		retry = 32;
> +		while (retry--) {
> +			ret = mtk_dp_aux_do_transfer(mtk_dp, is_read,
> request,
> +						     msg->address +
> accessed_bytes,
> +						     msg->buffer +
> accessed_bytes, 0);
> +			if (ret == 0)
> +				break;
> +			usleep_range(500, 600);
> +		}
>  	} else {
>  		while (accessed_bytes < msg->size) {
>  			size_t to_access =
>  				min_t(size_t, DP_AUX_MAX_PAYLOAD_BYTES,
>  				      msg->size - accessed_bytes);
> +			retry = 32;
>  			while (retry--) {
>  				ret = mtk_dp_aux_do_transfer(mtk_dp,
>  							     is_read,
> request,
> @@ -2066,7 +2073,7 @@ static ssize_t mtk_dp_aux_transfer(struct
> drm_dp_aux *mtk_aux,
>  							     to_access)
> ;
>  				if (ret == 0)
>  					break;
> -				usleep_range(50, 100);
> +				usleep_range(500, 600);
>  			}
>  			if (!retry || ret) {
>  				drm_info(mtk_dp->drm_dev,

Reviewed-by: Rex-BC Chen <rex-bc.chen@...iatek.com>