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

[CK Hu]

Hi, Guillaume:

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 void mtk_dp_read_link_status(struct mtk_dp *mtk_dp,
> +				    u8
> link_status[DP_LINK_STATUS_SIZE])
> +{
> +	drm_dp_dpcd_read(&mtk_dp->aux, DP_LANE0_1_STATUS, link_status,
> +			 DP_LINK_STATUS_SIZE);
> +}
> +
> +static int mtk_dp_train_tps_1(struct mtk_dp *mtk_dp,
> +			      u8 target_lane_count, int
> *iteration_count, u8 *lane_adjust,  int *status_control, u8
> *prev_lane_adjust)
> +{
> +	int ret;
> +	u8 val;
> +	u8 link_status[DP_LINK_STATUS_SIZE] = {};
> +
> +	ret = mtk_dp_training_set_scramble(mtk_dp, false);
> +	if (ret)
> +		return ret;
> +
> +	if (*status_control == 0) {
> +		ret = mtk_dp_train_set_pattern(mtk_dp, 1);
> +		if (ret)
> +			return ret;
> +
> +		val = DP_LINK_SCRAMBLING_DISABLE |
> +			DP_TRAINING_PATTERN_1;
> +		drm_dp_dpcd_writeb(&mtk_dp->aux,
> +				   DP_TRAINING_PATTERN_SET,
> +				DP_LINK_SCRAMBLING_DISABLE |
> +				DP_TRAINING_PATTERN_1);
> +		drm_dp_dpcd_read(&mtk_dp->aux,
> +				 DP_ADJUST_REQUEST_LANE0_1,
> +				lane_adjust,
> +				sizeof(*lane_adjust) * 2);
> +
> +		mtk_dp_train_update_swing_pre(mtk_dp,
> +					      target_lane_count,
> lane_adjust);
> +		*status_control = 1;
> +		(*iteration_count)++;
> +	}
> +
> +	drm_dp_link_train_clock_recovery_delay(&mtk_dp->aux,
> +					       mtk_dp->rx_cap);
> +	mtk_dp_read_link_status(mtk_dp, link_status);

drm_dp_dpcd_read_link_status(&mtk_dp->aux, link_status);

> +
> +	if (drm_dp_clock_recovery_ok(link_status,
> +				     target_lane_count)) {
> +		mtk_dp->train_info.cr_done = true;
> +		*iteration_count = 1;
> +		dev_dbg(mtk_dp->dev, "Link train CR pass\n");
> +		return 0;
> +	} else if (*prev_lane_adjust == link_status[4]) {
> +		(*iteration_count)++;
> +		if (*prev_lane_adjust &
> DP_ADJUST_VOLTAGE_SWING_LANE0_MASK) {
> +			dev_dbg(mtk_dp->dev, "Link train CQ fail\n");
> +			return -EINVAL;
> +		}
> +	} else {
> +		*prev_lane_adjust = link_status[4];
> +	}
> +	return -EAGAIN;
> +}
> +
> +static int mtk_dp_train_tps_2_3(struct mtk_dp *mtk_dp, u8
> target_linkrate,
> +				u8 target_lane_count, int
> *iteration_count, u8 *lane_adjust,  int *status_control, u8
> *prev_lane_adjust)
> +{
> +	int ret;
> +	u8 val;
> +	u8 link_status[DP_LINK_STATUS_SIZE] = {};
> +
> +	if (*status_control == 1) {
> +		if (mtk_dp->train_info.tps4) {
> +			ret = mtk_dp_train_set_pattern(mtk_dp, 4);
> +			if (ret)
> +				return -EINVAL;
> +
> +			val = DP_TRAINING_PATTERN_4;
> +		} else if (mtk_dp->train_info.tps3) {
> +			ret = mtk_dp_train_set_pattern(mtk_dp, 3);
> +			if (ret)
> +				return -EINVAL;
> +
> +			val = DP_LINK_SCRAMBLING_DISABLE |
> +				DP_TRAINING_PATTERN_3;
> +		} else {
> +			ret = mtk_dp_train_set_pattern(mtk_dp, 2);
> +			if (ret)
> +				return -EINVAL;
> +
> +			val = DP_LINK_SCRAMBLING_DISABLE |
> +				DP_TRAINING_PATTERN_2;
> +		}
> +		drm_dp_dpcd_writeb(&mtk_dp->aux,
> +				   DP_TRAINING_PATTERN_SET,
> +				val);
> +
> +		drm_dp_dpcd_read(&mtk_dp->aux,
> +				 DP_ADJUST_REQUEST_LANE0_1,
> +				lane_adjust,
> +				sizeof(*lane_adjust) * 2);
> +
> +		mtk_dp_train_update_swing_pre(mtk_dp,
> +					      target_lane_count,
> lane_adjust);
> +		*status_control = 2;
> +		(*iteration_count)++;
> +	}
> +
> +	drm_dp_link_train_channel_eq_delay(&mtk_dp->aux,
> +					   mtk_dp->rx_cap);
> +
> +	mtk_dp_read_link_status(mtk_dp, link_status);

drm_dp_dpcd_read_link_status(&mtk_dp->aux, link_status);

Regards,
CK

> +
> +	if (!drm_dp_clock_recovery_ok(link_status,
> +				      target_lane_count)) {
> +		mtk_dp->train_info.cr_done = false;
> +		mtk_dp->train_info.eq_done = false;
> +		dev_dbg(mtk_dp->dev, "Link train EQ fail\n");
> +		return -EINVAL;
> +	}
> +
> +	if (drm_dp_channel_eq_ok(link_status,
> +				 target_lane_count)) {
> +		mtk_dp->train_info.eq_done = true;
> +		dev_dbg(mtk_dp->dev, "Link train EQ pass\n");
> +		return 0;
> +	}
> +
> +	if (*prev_lane_adjust == link_status[4])
> +		(*iteration_count)++;
> +	else
> +		*prev_lane_adjust = link_status[4];
> +
> +	return -EAGAIN;
> +}
> +
>