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

Rex-BC Chen
2022-07-26T06:43:10Z

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.

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;
> > +}
> > +
>
>