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

[CK Hu <ck.hu@mediatek.com>]

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 <jitao.shi@mediatek.com>
> 
> Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> Signed-off-by: Guillaume Ranquet <granquet@baylibre.com>
> [Bo-Chen: Cleanup the drivers and modify comments from reviewers]
> Signed-off-by: Bo-Chen Chen <rex-bc.chen@mediatek.com>
> ---

[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.

> +	if (!irq_status)
> +		return IRQ_HANDLED;
> +
> +	connected = mtk_dp_plug_state(mtk_dp);
> +	if (connected || !train_info->cable_plugged_in)
> +		train_info->irq_sta.hpd_disconnect  = false;
> +	else if (!connected || train_info->cable_plugged_in)
> +		train_info->irq_sta.hpd_connect = false;
> +
> +	if (!(train_info->irq_sta.hpd_connect ||
> +	      train_info->irq_sta.hpd_disconnect))
> +		return IRQ_WAKE_THREAD;
> +
> +	if (train_info->irq_sta.hpd_connect) {
> +		train_info->irq_sta.hpd_connect = false;
> +		train_info->cable_plugged_in = true;
> +	} else {
> +		train_info->irq_sta.hpd_disconnect = false;
> +		train_info->cable_plugged_in = false;
> +		mtk_dp->train_state = MTK_DP_TRAIN_STATE_TRAINING;
> +	}
> +	train_info->cable_state_change = true;
> +
> +	return IRQ_WAKE_THREAD;
> +}
> +

[snip]

> +
> +static ssize_t mtk_dp_aux_transfer(struct drm_dp_aux *mtk_aux,
> +				   struct drm_dp_aux_msg *msg)
> +{
> +	struct mtk_dp *mtk_dp;
> +	bool is_read;
> +	u8 request;
> +	size_t accessed_bytes = 0;
> +	int ret = 0;
> +
> +	mtk_dp = container_of(mtk_aux, struct mtk_dp, aux);
> +
> +	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.

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;
> +}
> +