[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 at 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 <jason-jh.lin at mediatek.com>.
> 
> Signed-off-by: Markus Schneider-Pargmann <msp at baylibre.com>
> Signed-off-by: Guillaume Ranquet <granquet at baylibre.com>
> ---

[snip]

> +
> +static irqreturn_t mtk_dp_hpd_event_thread(int hpd, void *dev)
> +{
> +	struct mtk_dp *mtk_dp = dev;
> +	int event;
> +	u8 buf[DP_RECEIVER_CAP_SIZE] = {};
> +
> +	event = mtk_dp_plug_state(mtk_dp) ? connector_status_connected
> :
> +						  connector_status_disc
> onnected;
> +
> +	if (event < 0)

event is always > 0, isn't it?

> +		return IRQ_HANDLED;
> +
> +	if (mtk_dp->drm_dev) {
> +		dev_info(mtk_dp->dev, "drm_helper_hpd_irq_event\n");
> +		drm_helper_hpd_irq_event(mtk_dp->bridge.dev);

I think this ISR would come once. If bridge has not attached, the drm
core would lost this event. Maybe you should enable eDP hardware after
bridge attached or send this event when attached.

> +	}
> +
> +	if (mtk_dp->train_info.cable_state_change) {

Executing this thread imply cable_state_change = true, so drop
cable_state_change.

> +		mtk_dp->train_info.cable_state_change = false;
> +
> +		mtk_dp->train_state = MTK_DP_TRAIN_STATE_STARTUP;
> +
> +		if (!mtk_dp->train_info.cable_plugged_in ||
> +		    !mtk_dp_plug_state(mtk_dp)) {

I do not like two variable to present one thing. If

mtk_dp->train_info.cable_plugged_in = false
and
mtk_dp_plug_state(mtk_dp) = ture

What does this mean? I think this mean 'now' is connected because
cable_plugged_in is old information and mtk_dp_plug_state() is current
information.

But I would like to keep cable_plugged_in and drop mtk_dp_plug_state()
because cable_plugged_in would be changed in isr and it would be the
same as mtk_dp_plug_state().

Regards,
CK

> +			mtk_dp_video_mute(mtk_dp, true);
> +
> +			mtk_dp_initialize_priv_data(mtk_dp);
> +			mtk_dp_set_idle_pattern(mtk_dp, true);
> +			if (mtk_dp->has_fec)
> +				mtk_dp_fec_enable(mtk_dp, false);
> +
> +			mtk_dp_update_bits(mtk_dp,
> MTK_DP_TOP_PWR_STATE,
> +					   DP_PWR_STATE_BANDGAP_TPLL,
> +					   DP_PWR_STATE_MASK);
> +		} else {
> +			mtk_dp_update_bits(mtk_dp,
> MTK_DP_TOP_PWR_STATE,
> +					   DP_PWR_STATE_BANDGAP_TPLL_LA
> NE,
> +					   DP_PWR_STATE_MASK);
> +			drm_dp_read_dpcd_caps(&mtk_dp->aux, buf);
> +			mtk_dp->train_info.link_rate =
> +				min_t(int, mtk_dp->max_linkrate,
> +				      buf[mtk_dp->max_linkrate]);
> +			mtk_dp->train_info.lane_count =
> +				min_t(int, mtk_dp->max_lanes,
> +				      drm_dp_max_lane_count(buf));
> +		}
> +	}
> +
> +	if (mtk_dp->train_info.irq_status & MTK_DP_HPD_INTERRUPT) {
> +		dev_dbg(mtk_dp->dev, "MTK_DP_HPD_INTERRUPT\n");
> +		mtk_dp->train_info.irq_status &= ~MTK_DP_HPD_INTERRUPT;
> +		mtk_dp_hpd_sink_event(mtk_dp);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +