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

[CK Hu]

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 at 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 at mediatek.com>
> > > 
> > > Signed-off-by: Markus Schneider-Pargmann <msp at baylibre.com>
> > > Signed-off-by: Guillaume Ranquet <granquet at baylibre.com>
> > > Signed-off-by: Bo-Chen Chen <rex-bc.chen at 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

> 
> 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;
> > > +}
> > > +
> > 
> > 
> 
>