Re: [PATCH v10 18/21] drm/mediatek: Add mt8195 Embedded DisplayPort driver

[Rex-BC Chen]

On Tue, 2022-06-07 at 16:12 +0800, CK Hu wrote:
> Hi, Rex:
> 
> On Mon, 2022-05-23 at 12:47 +0200, Guillaume Ranquet wrote:
> > From: Markus Schneider-Pargmann <msp@xxxxxxxxxxxx>
> > 
> > This patch adds a 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
> > Jason-JH.Lin <jason-jh.lin@xxxxxxxxxxxx>.
> > 
> > Signed-off-by: Markus Schneider-Pargmann <msp@xxxxxxxxxxxx>
> > Signed-off-by: Guillaume Ranquet <granquet@xxxxxxxxxxxx>
> > ---
> 
> [snip]
> 
> > +
> > +static int mtk_dp_train_start(struct mtk_dp *mtk_dp)
> > +{
> > +	int ret = 0;
> > +	u8 lane_count;
> > +	u8 link_rate;
> > +	u8 train_limit;
> > +	u8 max_link_rate;
> > +	u8 plug_wait;
> > +
> > +	for (plug_wait = 7; !mtk_dp_plug_state(mtk_dp) && plug_wait >
> > 0;
> > +	     --plug_wait)
> > +		/* Avoid short pulses on the HPD isr */
> > +		usleep_range(1000, 5000);
> > +	if (plug_wait == 0) {
> > +		mtk_dp->train_state = MTK_DP_TRAIN_STATE_DPIDLE;
> 
> After return, mtk_dp->train_state would be set to
> MTK_DP_TRAIN_STATE_DPIDLE, so drop this.
> 

ok, I will do this.

> > +		return -ENODEV;
> > +	}
> > +
> > +	link_rate = mtk_dp->rx_cap[1];
> > +	lane_count = mtk_dp->rx_cap[2] & 0x1F;
> > +
> > +	mtk_dp->train_info.link_rate = min(mtk_dp->max_linkrate,
> > link_rate);
> > +	mtk_dp->train_info.lane_count = min(mtk_dp->max_lanes,
> > lane_count);
> > +	link_rate = mtk_dp->train_info.link_rate;
> > +	lane_count = mtk_dp->train_info.lane_count;
> > +
> > +	switch (link_rate) {
> > +	case MTK_DP_LINKRATE_RBR:
> > +	case MTK_DP_LINKRATE_HBR:
> > +	case MTK_DP_LINKRATE_HBR2:
> > +	case MTK_DP_LINKRATE_HBR25:
> > +	case MTK_DP_LINKRATE_HBR3:
> > +		break;
> > +	default:
> > +		mtk_dp->train_info.link_rate = MTK_DP_LINKRATE_HBR3;
> > +		break;
> > +	};
> > +
> > +	max_link_rate = link_rate;
> > +	for (train_limit = 6; train_limit > 0; train_limit--) {
> > +		mtk_dp->train_info.cr_done = false;
> > +		mtk_dp->train_info.eq_done = false;
> > +
> > +		mtk_dp_train_change_mode(mtk_dp);
> > +		ret = mtk_dp_train_flow(mtk_dp, link_rate, lane_count);
> > +		if (ret)
> > +			return ret;
> > +
> > +		if (!mtk_dp->train_info.cr_done) {
> > +			switch (link_rate) {
> > +			case MTK_DP_LINKRATE_RBR:
> > +				lane_count = lane_count / 2;
> > +				link_rate = max_link_rate;
> > +				if (lane_count == 0) {
> > +					mtk_dp->train_state =
> > +						MTK_DP_TRAIN_STATE_DPID
> > LE;
> 
> After return, mtk_dp->train_state would be set to
> MTK_DP_TRAIN_STATE_DPIDLE, so drop this.
> 
> Regards,
> CK
> 

ok.

> > +					return -EIO;
> > +				}
> > +				break;
> > +			case MTK_DP_LINKRATE_HBR:
> > +				link_rate = MTK_DP_LINKRATE_RBR;
> > +				break;
> > +			case MTK_DP_LINKRATE_HBR2:
> > +				link_rate = MTK_DP_LINKRATE_HBR;
> > +				break;
> > +			case MTK_DP_LINKRATE_HBR3:
> > +				link_rate = MTK_DP_LINKRATE_HBR2;
> > +				break;
> > +			default:
> > +				return -EINVAL;
> > +			};
> > +		} else if (!mtk_dp->train_info.eq_done) {
> > +			if (lane_count == 0)
> > +				return -EIO;
> > +
> > +			lane_count /= 2;
> > +		} else {
> > +			break;
> > +		}
> > +	}
> > +
> > +	if (train_limit == 0)
> > +		return -ETIMEDOUT;
> > +
> > +	return 0;
> > +}
> > +
> 
>