Re: [PATCH v14 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort driver

Rex-BC Chen
2022-07-26T10:07:09Z

On Tue, 2022-07-26 at 17:34 +0800, CK Hu wrote:
> On Tue, 2022-07-26 at 14:42 +0800, Rex-BC Chen wrote:
> > On Mon, 2022-07-25 at 17:16 +0800, CK Hu wrote:
> > > Hi, Bo-Chen:
> > >
> > > On Tue, 2022-07-12 at 19:12 +0800, Bo-Chen Chen wrote:
> > > > From: Markus Schneider-Pargmann <msp@baylibre.com>
> > > >
> > > > This patch adds a embedded displayport driver for the MediaTek
> > > > mt8195
> > > > SoC.
> > > >
> > > > It supports the MT8195, the embedded DisplayPort units. It
> > > > offers
> > > > DisplayPort 1.4 with up to 4 lanes.
> > > >
> > > > The driver creates a child device for the phy. The child device
> > > > will
> > > > never exist without the parent being active. As they are
> > > > sharing
> > > > a
> > > > register range, the parent passes a regmap pointer to the child
> > > > so
> > > > that
> > > > both can work with the same register range. The phy driver sets
> > > > device
> > > > data that is read by the parent to get the phy device that can
> > > > be
> > > > used
> > > > to control the phy properties.
> > > >
> > > > This driver is based on an initial version by
> > > > Jitao shi <jitao.shi@mediatek.com>
> > > >
> > > > Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> > > > Signed-off-by: Guillaume Ranquet <granquet@baylibre.com>
> > > > Signed-off-by: Bo-Chen Chen <rex-bc.chen@mediatek.com>
> > > > ---
> > >
> > > [snip]
> > >
> > > > +
> > > > +static int mtk_dp_training(struct mtk_dp *mtk_dp)
> > > > +{
> > > > + short max_retry = 50;
> > > > + int ret;
> > > > +
> > > > + do {
> > > > + ret = mtk_dp_train_start(mtk_dp);
> > > > + if (!ret)
> > > > + break;
> > > > + else if (ret != -EAGAIN)
> > > > + return ret;
> > > > + } while (--max_retry);
> > >
> > > mtk_dp_train_start() would never return -EAGAIN, so drop this
> > > while
> > > loop.
> > >
> > > Regards,
> > > CK
> > >
> >
> > Hello CK,
> >
> > the function will not return -EAGAIN, but we still want to retry 50
> > times if mtk_dp_train_start() is failed. If we retry 50 times and
> > it
> > is
> > still failed. We can confirm there are some issues for the device.
> >
> > I will remove the else if of -EAGAIN and keep th while loop.
>
> In this version, it never retry. And I believe you've tested this no-
> retry version. If this no-retry version works fine, why do you insist
> on retry? If you really need retry, merge this retry into
> mtk_dp_train_start() because mtk_dp_train_start() have already retry.
>
> Regards,
> CK
>

Hello Ck,

There are many different devices we are not testing for DP devices.
I think we need to keep this.
This retry is for restart with init state.

I think it's better to keep it here and it's more clear.

I will remain the comments above, and I think it's enough.

BRs,
Bo-Chen

> >
> > BRs,
> > Bo-Chen
> > > >
> > > > + if (!max_retry)
> > > > + return -ETIMEDOUT;
> > > > +
> > > > + ret = mtk_dp_video_config(mtk_dp);
> > > > + if (ret)
> > > > + return ret;
> > > > + mtk_dp_video_enable(mtk_dp, true);
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > >
> > >
> >
> >
>
>