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

[Rex-BC Chen <rex-bc.chen@mediatek.com>]

On Wed, 2022-06-15 at 10:58 +0800, CK Hu wrote:
> 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.
> 

Hello CK,

ok, I will drop this.

> > +			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.
> 

ok

> > +	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.
> 

ok, I will drop this

BRs,
Bo-Chen

> 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;
> > +}
> > +
> 
>