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

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Date:   Mon, 3 Apr 2023 11:49:19 +0800
From:   Chun-Kuang Hu <chunkuang.hu@...nel.org>
To:     xinlei.lee@...iatek.com
Cc:     chunkuang.hu@...nel.org, p.zabel@...gutronix.de, airlied@...ux.ie,
        daniel@...ll.ch, matthias.bgg@...il.com,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH] drm/mediatek: dp: change the aux retries times when
 receiving AUX_DEFER

Hi, Xinlei:

<xinlei.lee@...iatek.com> 於 2023年3月29日 週三 下午2:43寫道：
>
> From: Xinlei Lee <xinlei.lee@...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.
>
> The drm_dp_i2c_do_msg() function in the drm_dp_helper.c file will
> judge the status of the msg->reply parameter passed to aux_transfer
> ange-the-aux-retries-times-when-re.patchfor different processing.
>
> Fixes: f70ac097a2cf ("drm/mediatek: Add MT8195 Embedded DisplayPort driver")
> Signed-off-by: Xinlei Lee <xinlei.lee@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dp.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
> index 1f94fcc144d3..767b71da31a4 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
> @@ -806,10 +806,9 @@ static int mtk_dp_aux_wait_for_completion(struct mtk_dp *mtk_dp, bool is_read)
>  }
>
>  static int mtk_dp_aux_do_transfer(struct mtk_dp *mtk_dp, bool is_read, u8 cmd,
> -                                 u32 addr, u8 *buf, size_t length)
> +                                 u32 addr, u8 *buf, size_t length, u8 *reply_cmd)
>  {
>         int ret;
> -       u32 reply_cmd;
>
>         if (is_read && (length > DP_AUX_MAX_PAYLOAD_BYTES ||
>                         (cmd == DP_AUX_NATIVE_READ && !length)))
> @@ -841,10 +840,10 @@ static int mtk_dp_aux_do_transfer(struct mtk_dp *mtk_dp, bool is_read, u8 cmd,
>         /* Wait for feedback from sink device. */
>         ret = mtk_dp_aux_wait_for_completion(mtk_dp, is_read);
>
> -       reply_cmd = mtk_dp_read(mtk_dp, MTK_DP_AUX_P0_3624) &
> -                   AUX_RX_REPLY_COMMAND_AUX_TX_P0_MASK;
> +       *reply_cmd = mtk_dp_read(mtk_dp, MTK_DP_AUX_P0_3624) &
> +                    AUX_RX_REPLY_COMMAND_AUX_TX_P0_MASK;
>
> -       if (ret || reply_cmd) {
> +       if (ret) {
>                 u32 phy_status = mtk_dp_read(mtk_dp, MTK_DP_AUX_P0_3628) &
>                                  AUX_RX_PHY_STATE_AUX_TX_P0_MASK;
>                 if (phy_status != AUX_RX_PHY_STATE_AUX_TX_P0_RX_IDLE) {
> @@ -2070,7 +2069,7 @@ static ssize_t mtk_dp_aux_transfer(struct drm_dp_aux *mtk_aux,
>                 ret = mtk_dp_aux_do_transfer(mtk_dp, is_read, request,
>                                              msg->address + accessed_bytes,
>                                              msg->buffer + accessed_bytes,
> -                                            to_access);
> +                                            to_access, &msg->reply);
>
>                 if (ret) {
>                         drm_info(mtk_dp->drm_dev,
> @@ -2080,7 +2079,6 @@ static ssize_t mtk_dp_aux_transfer(struct drm_dp_aux *mtk_aux,
>                 accessed_bytes += to_access;
>         } while (accessed_bytes < msg->size);
>
> -       msg->reply = DP_AUX_NATIVE_REPLY_ACK | DP_AUX_I2C_REPLY_ACK;

In your description, you just mention the retry count is 7 times, but
you does not mention you should change the reply. Why you modify this?
And where is the 7 times retry?

Regards,
Chun-Kuang.

>         return msg->size;
>  err:
>         msg->reply = DP_AUX_NATIVE_REPLY_NACK | DP_AUX_I2C_REPLY_NACK;
> --
> 2.18.0
>