Re: [PATCH] drm/mediatek: dp: change the aux retries times when receiving AUX_DEFER

[Chun-Kuang Hu]

Hi, Xinlei:

Xinlei Lee (李昕磊) <Xinlei.Lee@xxxxxxxxxxxx> 於 2023年4月3日 週一 下午5:18寫道：
>
> On Mon, 2023-04-03 at 11:49 +0800, Chun-Kuang Hu wrote:
> > External email : Please do not click links or open attachments until
> > you have verified the sender or the content.
> >
> >
> > Hi, Xinlei:
> >
> > <xinlei.lee@xxxxxxxxxxxx> 於 2023年3月29日 週三 下午2:43寫道：
> > >
> > > From: Xinlei Lee <xinlei.lee@xxxxxxxxxxxx>
> > >
> > > 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@xxxxxxxxxxxx>
> > > ---
> > >  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
> > >
>
> Hi CK:
>
> Thanks for your review!
>
> This patch is to fix some DP sinks that return AUX_DEFER, and the dp
> driver does not handle it according to the specification. DP_v1.4a
> spec 2.8.1.2 describes that if the sink returns AUX_DEFER, DPTX may
> retry later:
>
> The logic before the modification is that reply_cmd returns ETIMEDOUT
> if it is not AUX_ACK after the read operation, without considering the
> retry operation when returning AUX_DEFER;
>
> The modified logic is to add parameters to mtk_dp_aux_do_transfer() to
> store the return value of the sink. In the dmr_dp_helper.c file,
> drm_dp_i2c_do_msg calls aux->transfer and then performs retry
> operation according to msg->reply. The 7 times specified in the spec
> are also in this function defined in (max_retries).

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

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

Regards,
Chun-Kuang.

>
> Best Regards!
> xinlei