Re: [PATCH v11 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort driver

Hi, Bo-Chen:

On Fri, 2022-06-10 at 18:55 +0800, Bo-Chen Chen wrote:

From: Markus Schneider-Pargmann <msp@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 [off-list ref]

Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Signed-off-by: Guillaume Ranquet <redacted>
[Bo-Chen: Cleanup the drivers and modify comments from reviewers]
Signed-off-by: Bo-Chen Chen <redacted>
---

[snip]

+
+static int mtk_dp_train_flow(struct mtk_dp *mtk_dp, u8
target_link_rate,
+			     u8 target_lane_count)
+{
+	u8 lane_adjust[2] = {};
+	bool pass_tps1 = false;
+	bool pass_tps2_3 = false;
+	int train_retries;
+	int status_control;
+	int iteration_count;
+	int ret;
+	u8 prev_lane_adjust;
+
+	drm_dp_dpcd_writeb(&mtk_dp->aux, DP_LINK_BW_SET,
target_link_rate);
+	drm_dp_dpcd_writeb(&mtk_dp->aux, DP_LANE_COUNT_SET,
+			   target_lane_count |
DP_LANE_COUNT_ENHANCED_FRAME_EN);
+
+	if (mtk_dp->train_info.sink_ssc)
+		drm_dp_dpcd_writeb(&mtk_dp->aux, DP_DOWNSPREAD_CTRL,
+				   DP_SPREAD_AMP_0_5);
+
+	train_retries = 0;
+	status_control = 0;
+	iteration_count = 1;
+	prev_lane_adjust = 0xFF;
+
+	mtk_dp_set_lanes(mtk_dp, target_lane_count / 2);
+	ret = mtk_dp_phy_configure(mtk_dp, target_link_rate,
target_lane_count);
+	if (ret)
+		return -EINVAL;
+
+	dev_dbg(mtk_dp->dev,
+		"Link train target_link_rate = 0x%x, target_lane_count
= 0x%x\n",
+		target_link_rate, target_lane_count);
+
+	do {
+		train_retries++;
+		if (!mtk_dp->train_info.cable_plugged_in ||
+		    mtk_dp->train_info.irq_sta.hpd_disconnect) {

In mtk_dp_hpd_isr_handler(), train_info.irq_sta.hpd_disconnect would
finally be set to false, so you need not to check it here. So remove it
here.

+			return -ENODEV;
+		}
+
+		if (mtk_dp->train_state < MTK_DP_TRAIN_STATE_TRAINING)
+			return -EAGAIN;
+
+		if (!pass_tps1) {
+			ret = mtk_dp_train_tps_1(mtk_dp,
target_lane_count,
+						 &iteration_count,
lane_adjust,
+						 &status_control,
+						 &prev_lane_adjust);
+			if (!ret) {
+				pass_tps1 = true;
+				train_retries = 0;
+			} else if (ret == -EINVAL) {
+				break;
+			}
+		} else {
+			ret = mtk_dp_train_tps_2_3(mtk_dp,
target_link_rate,
+						   target_lane_count,
+						   &iteration_count,
+						   lane_adjust,
&status_control,
+						   &prev_lane_adjust);
+			if (!ret) {
+				pass_tps2_3 = true;
+				break;
+			} else if (ret == -EINVAL) {
+				break;
+			}
+		}
+
+		drm_dp_dpcd_read(&mtk_dp->aux,
DP_ADJUST_REQUEST_LANE0_1,
+				 lane_adjust, sizeof(lane_adjust));
+		mtk_dp_train_update_swing_pre(mtk_dp,
target_lane_count,
+					      lane_adjust);
+	} while (train_retries < MTK_DP_TRAIN_RETRY_LIMIT &&
+		 iteration_count < MTK_DP_TRAIN_MAX_ITERATIONS);
+
+	drm_dp_dpcd_writeb(&mtk_dp->aux, DP_TRAINING_PATTERN_SET,
+			   DP_TRAINING_PATTERN_DISABLE);
+	ret = mtk_dp_train_set_pattern(mtk_dp, 0);
+	if (ret)
+		return -EINVAL;
+
+	if (!pass_tps2_3)
+		return -ETIMEDOUT;
+
+	mtk_dp->train_info.link_rate = target_link_rate;
+	mtk_dp->train_info.lane_count = target_lane_count;
+
+	mtk_dp_training_set_scramble(mtk_dp, true);
+
+	drm_dp_dpcd_writeb(&mtk_dp->aux, DP_LANE_COUNT_SET,
+			   target_lane_count |
+				   DP_LANE_COUNT_ENHANCED_FRAME_EN);
+	mtk_dp_set_enhanced_frame_mode(mtk_dp, true);
+
+	return ret;
+}
+

[snip]

+
+/*
+ * We need to handle HPD signal in eDP even though eDP is a always
connected
+ * device. Besides connected status, there is another feature for
HPD signal -
+ * HPD pulse: it presents an IRQ from sink devices to source devices
(Refer to
+ * 5.1.4 of DP1.4 spec).
+ */
+static irqreturn_t mtk_dp_hpd_isr_handler(struct mtk_dp *mtk_dp)
+{
+	bool connected;
+	u32 irq_status = mtk_dp_swirq_get_clear(mtk_dp) |
+			 mtk_dp_hwirq_get_clear(mtk_dp);
+	struct mtk_dp_train_info *train_info = &mtk_dp->train_info;
+
+	if (irq_status & MTK_DP_HPD_INTERRUPT)
+		train_info->irq_sta.hpd_inerrupt = true;
+	if (irq_status & MTK_DP_HPD_CONNECT)
+		train_info->irq_sta.hpd_connect = true;
+	if (irq_status & MTK_DP_HPD_DISCONNECT)
+		train_info->irq_sta.hpd_disconnect = true;
+

train_info->irq_sta.hpd_connect is used only in this function, so let
hpd_connect to be local variable.

[snip]

In mtk_dp_hpd_isr_handler(), train_info.irq_sta.hpd_disconnect would
finally be set to false, so you need not to check it here. So remove it
here.

Regards,
CK

+		ret = -EAGAIN;
+		goto err;
+	}
+
+	switch (msg->request) {
+	case DP_AUX_I2C_MOT:
+	case DP_AUX_I2C_WRITE:
+	case DP_AUX_NATIVE_WRITE:
+	case DP_AUX_I2C_WRITE_STATUS_UPDATE:
+	case DP_AUX_I2C_WRITE_STATUS_UPDATE | DP_AUX_I2C_MOT:
+		request = msg->request &
~DP_AUX_I2C_WRITE_STATUS_UPDATE;
+		is_read = false;
+		break;
+	case DP_AUX_I2C_READ:
+	case DP_AUX_NATIVE_READ:
+	case DP_AUX_I2C_READ | DP_AUX_I2C_MOT:
+		request = msg->request;
+		is_read = true;
+		break;
+	default:
+		drm_err(mtk_aux->drm_dev, "invalid aux cmd = %d\n",
+			msg->request);
+		ret = -EINVAL;
+		goto err;
+	}
+
+	if (msg->size == 0) {
+		ret = mtk_dp_aux_do_transfer(mtk_dp, is_read, request,
+					     msg->address +
accessed_bytes,
+					     msg->buffer +
accessed_bytes, 0);
+	} else {
+		while (accessed_bytes < msg->size) {
+			size_t to_access =
+				min_t(size_t, DP_AUX_MAX_PAYLOAD_BYTES,
+				      msg->size - accessed_bytes);
+
+			ret = mtk_dp_aux_do_transfer(mtk_dp, is_read,
request,
+						     msg->address +
accessed_bytes,
+						     msg->buffer +
accessed_bytes,
+						     to_access);
+
+			if (ret) {
+				drm_info(mtk_dp->drm_dev,
+					 "Failed to do AUX transfer:
%d\n", ret);
+				break;
+			}
+			accessed_bytes += to_access;
+		}
+	}
+err:
+	if (ret) {
+		msg->reply = DP_AUX_NATIVE_REPLY_NACK |
DP_AUX_I2C_REPLY_NACK;
+		return ret;
+	}
+
+	msg->reply = DP_AUX_NATIVE_REPLY_ACK | DP_AUX_I2C_REPLY_ACK;
+	return msg->size;
+}
+

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel