Hi, Rex:

On Mon, 2022-05-23 at 12:47 +0200, Guillaume Ranquet wrote:

From: Markus Schneider-Pargmann <msp@baylibre.com>

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 [off-list ref].

Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Signed-off-by: Guillaume Ranquet <redacted>
---

[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;
+}
+