[PATCH v13 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort driver

[Rex-BC Chen]

On Thu, 2022-07-07 at 13:14 +0800, CK Hu wrote:
> Hi, Bo-Chen:
> 
> On Fri, 2022-07-01 at 14:28 +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 ssize_t mtk_dp_hpd_sink_event(struct mtk_dp *mtk_dp)
> 
> The caller never use the return value, so let this function to void.
> 
> > +{
> > +	ssize_t ret;
> > +	u8 sink_count;
> > +	u8 link_status[DP_LINK_STATUS_SIZE] = {};
> > +	u32 sink_count_reg = DP_SINK_COUNT_ESI;
> > +	u32 link_status_reg = DP_LANE0_1_STATUS;
> > +
> > +	ret = drm_dp_dpcd_readb(&mtk_dp->aux, sink_count_reg,
> > &sink_count);
> 
> You read sink_count but never use it, so this read is redundant.
> Remove
> it.
> 

Hello CK,

this is a pre-request for the following codes, so I think we need to
keep this.

If we failed to read sink_count, we don't need to do the driver under
this.

> > +	if (ret < 1) {
> > +		drm_err(mtk_dp->drm_dev, "Read sink count failed\n");
> > +		return ret == 0 ? -EIO : ret;
> > +	}
> > +
> > +	ret = drm_dp_dpcd_read(&mtk_dp->aux, link_status_reg,
> > link_status,
> > +			       sizeof(link_status));
> > +	if (!ret) {
> > +		drm_err(mtk_dp->drm_dev, "Read link status failed\n");
> > +		return ret;
> > +	}
> > +
> > +	drm_dp_channel_eq_ok(link_status, mtk_dp-
> > > train_info.lane_count);
> 
> This function just return true or false, and you does not process the
> return value, so this is redundant. Remove it.
> 

I will handle this in next version.

BRs,
Bo-Chen

> Regard,
> CK
> 
> > +
> > +	if (link_status[1] & DP_REMOTE_CONTROL_COMMAND_PENDING)
> > +		drm_dp_dpcd_writeb(&mtk_dp->aux,
> > DP_DEVICE_SERVICE_IRQ_VECTOR,
> > +				   DP_REMOTE_CONTROL_COMMAND_PENDING);
> > +
> > +	return 0;
> > +}
> 
>