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

[CK Hu]

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_hpd_sink_event(struct mtk_dp *mtk_dp)
> +{
> +	ssize_t ret;
> +	u8 sink_count;
> +	bool locked;
> +	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);
> +	if (ret < 0) {
> +		drm_err(mtk_dp->drm_dev, "Read sink count failed:
> %ld\n", ret);
> +		return 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:
> %ld\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	locked = drm_dp_channel_eq_ok(link_status,
> +				      mtk_dp->train_info.lane_count);
> +	if (!locked && mtk_dp->train_state >
> MTK_DP_TRAIN_STATE_TRAINING_PRE)

Before enter this function, mtk_dp->train_state is set to
MTK_DP_TRAIN_STATE_STARTUP, so this never happen, drop this.

> +		mtk_dp->train_state = MTK_DP_TRAIN_STATE_TRAINING_PRE;
> +
> +	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);
> +
> +	if (DP_GET_SINK_COUNT(sink_count) &&
> +	    (link_status[2] & DP_DOWNSTREAM_PORT_STATUS_CHANGED)) {
> +		mtk_dp->train_info.check_cap_count = 0;
> +		mtk_dp->train_state = MTK_DP_TRAIN_STATE_CHECKEDID;

Why change state from MTK_DP_TRAIN_STATE_STARTUP to
MTK_DP_TRAIN_STATE_CHECKEDID? In mtk_dp_train_handler(),
mtk_dp_parse_capabilities() is true then change to
MTK_DP_TRAIN_STATE_CHECKEDID. Give a reason why these two are
different.

Regards,
CK

> +		msleep(20);
> +	}
> +
> +	return 0;
> +}
> +