Re: [PATCH v2 00/10] Add HPD support for Rockchip Analogix DP

[Heiko Stübner]

Am Mittwoch, 5. August 2026, 06:06:48 Mitteleuropäische Sommerzeit schrieb Damon Ding:
> Hi Heiko,
> 
> On 8/5/2026 6:39 AM, Heiko Stübner wrote:
> > Hi Damon,
> > 
> > Am Dienstag, 4. August 2026, 10:17:07 Mitteleuropäische Sommerzeit schrieb Damon Ding:
> >> Display-connector mode (DP connector without HPD GPIO):
> >>
> >>    &edp_out_conn {
> >>        remote-endpoint = <&dp_con_in>;
> >>    };
> >>
> >>    dp-con {
> >>        compatible = "dp-connector";
> >>        label = "DP OUT";
> >>        type = "full-size";
> >>
> >>        port {
> >>            dp_con_in: endpoint {
> >>                remote-endpoint = <&edp_out_conn>;
> >>            };
> >>        };
> >>    };
> >>
> >> Display-connector mode (DP connector with HPD GPIO):
> >>
> >>    dp-con {
> >>        compatible = "dp-connector";
> >>        label = "DP OUT";
> >>        type = "full-size";
> >>        pinctrl-0 = <&edp0_hpd>;
> >>        pinctrl-names = "default";
> >>        hpd-gpios = <&gpio4 RK_PC1 GPIO_ACTIVE_HIGH>;
> >>
> >>        port {
> >>            dp_con_in: endpoint {
> >>                remote-endpoint = <&edp_out_conn>;
> >>            };
> >>        };
> >>    };
> >>
> >> All four configurations detect cable plug/unplug events correctly.
> 
> Thanks a lot for your testing and feedback. :-)
> 
> It seems my test setup gave me the false impression that those cases 
> worked well.
> 
> > 
> > hmm, it wasn't working entirely for me though and was still running into
> > issues when the display was unplugged on boot.
> > 
> 
> Are you seeing this boot‑unplug issue for both scenarios: DP‑connector 
> with HPD‑gpio paired with eDP without HPD‑gpio, and DP‑connector without 
> HPD‑gpio paired with eDP with HPD‑gpio? I.e. it wrongly reports 
> connected even with no display plugged in and proceeds into DRM 
> .atomic_enable()?

Yep it's different. The analogix-dp gpio-hpd works correctly,  because the
analogix driver can do gpiod_get_value() in analogix_dp_get_plug_in_status()

The dp-connector does not, as with the patch you pointed to, it lost
that ability. So on boot a plugged in display is not detected correctly
because there won't be a hotplug interrupt.

> 
> > I wiggled around a bit like in the diff below and am now getting correct
> > plug and unplug events.
> 
> Oh, I see. For the GPIO HPD case, the IRQ needs to be enabled early so 
> that plug‑in interrupts can be properly responded to. However GPIO HPD 
> does not require a runtime PM get. I will better separate these two 
> scenarios in the next version.
> 
> > 
> > But of course, as the dp-variant of the connector does not provide
> > a "detect" and just the "hpd" functionality, it's missing the initial state.
> > 
> > I'm currently not sure how to find out _if_ a panel is connected on boot.
> > 
> 
> Based on Dmitry's commit cb640b2ca546 ("drm/bridge: display‑connector: 
> don't set OP_DETECT for DisplayPorts"), HPD events from DP‑variant 
> connector should be handled by the upstream DP controller. Hence I added 
> analogix_dp_bridge_notify() to retrieve HPD status coming from downstream.
> 
> As expected, under the bridge‑connector framework, the detect result 
> from Analogix DP should in theory reflect the actual connection status.
> Let's dig into this boot‑time initial‑state issue together.

One idea I had was, is it possible to do a drm_dp_read_dpcd_caps()
read during bind/... to see if something answers?

Thanks for all your work
Heiko

> > In other review comments:
> > - the bridge could use devm_drm_of_get_bridge() as suggested in
> >    the documentation of drm_of_find_panel_or_bridge(), as that would
> >    remove the separate panel_bridge creation
> > - instead of using plat_data->next_bridge _inside_ the driver
> >    struct drm_bridge has a field next_bridge already.
> 
> Great suggestions, I will incorporate them for the next version 
> alongside Sashiko's comments.
> 
> Best regards,
> Damon
> 
> > 
> > 
> > Heiko
> > 
> > 
> > ------- 8< -------
> > diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > index 877e1b3ca7525..1388640a27de7 100644
> > --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > @@ -43,7 +43,7 @@ static const bool verify_fast_training;
> >   static bool analogix_dp_require_pm_for_hpd_irq(struct analogix_dp_device *dp)
> >   {
> >   	return analogix_dp_is_rockchip(dp->plat_data->dev_type) && !dp->hpd_gpiod &&
> > -	       !dp->force_hpd;
> > +	       !dp->hpd_bridge && !dp->force_hpd;
> >   }
> >   
> >   static void analogix_dp_init_dp(struct analogix_dp_device *dp)
> > @@ -72,7 +72,7 @@ static int analogix_dp_detect_hpd(struct analogix_dp_device *dp)
> >   	 * Trust connection status from downstream bridge (e.g.,
> >   	 * display-connector with hpd-gpios).
> >   	 */
> > -	if (dp->plat_data->next_bridge && dp->connection_notified)
> > +	if (dp->hpd_bridge && dp->connection_notified)
> >   		return 0;
> >   
> >   	while (timeout_loop < DP_TIMEOUT_LOOP_COUNT) {
> > @@ -926,10 +926,10 @@ analogix_dp_bridge_detect(struct drm_bridge *bridge, struct drm_connector *conne
> >   	 */
> >   	if (dp->plat_data->next_bridge && dp->last_bridge_is_panel)
> >   		status = connector_status_connected;
> > -
> > -	if (!analogix_dp_detect_hpd(dp))
> > +	else if (!analogix_dp_detect_hpd(dp))
> >   		status = connector_status_connected;
> >   
> > +printk("---> %s status %d\n", __func__, status);
> >   	return status;
> >   }
> >   
> > @@ -1044,7 +1044,7 @@ static int analogix_dp_set_bridge(struct analogix_dp_device *dp)
> >   		goto out_dp_init;
> >   	}
> >   
> > -	if (!analogix_dp_require_pm_for_hpd_irq(dp))
> > +	if (!analogix_dp_require_pm_for_hpd_irq(dp) && !dp->hpd_bridge)
> >   		enable_irq(dp->irq);
> >   	return 0;
> >   
> > @@ -1187,7 +1187,7 @@ static void analogix_dp_bridge_disable(struct drm_bridge *bridge)
> >   	if (dp->dpms_mode != DRM_MODE_DPMS_ON)
> >   		return;
> >   
> > -	if (!analogix_dp_require_pm_for_hpd_irq(dp))
> > +	if (!analogix_dp_require_pm_for_hpd_irq(dp) && !dp->hpd_bridge)
> >   		disable_irq(dp->irq);
> >   
> >   	analogix_dp_set_analog_power_down(dp, POWER_ALL, 1);
> > @@ -1264,6 +1264,7 @@ static void analogix_dp_bridge_notify(struct drm_bridge *bridge, struct drm_conn
> >   	struct analogix_dp_device *dp = to_dp(bridge);
> >   
> >   	dp->connection_notified = (status == connector_status_connected);
> > +printk("---> %s connection_notified %d\n", __func__, dp->connection_notified);
> >   }
> >   
> >   static const struct drm_bridge_funcs analogix_dp_bridge_funcs = {
> > @@ -1641,6 +1642,13 @@ static int analogix_dp_aux_done_probing(struct drm_dp_aux *aux)
> >   	if (ret && ret != -ENODEV)
> >   		return ret;
> >   
> > +	/*
> > +	 * There is a next link in the chain which is not a panel, we should
> > +	 * expect hotplug-information coming from there.
> > +	 */
> > +	if (plat_data->next_bridge && !drm_bridge_is_panel(plat_data->next_bridge))
> > +		dp->hpd_bridge = true;
> > +
> >   	return component_add(dp->dev, plat_data->ops);
> >   }
> >   
> > diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
> > index d0fb25e543ea0..ecca3b87b4456 100644
> > --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
> > +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.h
> > @@ -169,6 +169,7 @@ struct analogix_dp_device {
> >   	bool			fast_train_enable;
> >   	bool			psr_supported;
> >   	bool			last_bridge_is_panel;
> > +	bool			hpd_bridge;
> >   	bool			connection_notified;
> >   
> >   	u8 dpcd[DP_RECEIVER_CAP_SIZE];
> > diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> > index ec5950066f838..6f0d642739ffd 100644
> > --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> > +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
> > @@ -182,7 +182,7 @@ void analogix_dp_config_interrupt(struct analogix_dp_device *dp)
> >   	writel(0, dp->reg_base + ANALOGIX_DP_COMMON_INT_MASK_2);
> >   	writel(0, dp->reg_base + ANALOGIX_DP_COMMON_INT_MASK_3);
> >   
> > -	if (dp->hpd_gpiod) {
> > +	if (dp->hpd_gpiod || dp->hpd_bridge) {
> >   		analogix_dp_mute_hpd_interrupt(dp, HPD_IRQ);
> >   	} else {
> >   		/*
> > @@ -438,7 +438,7 @@ void analogix_dp_init_hpd(struct analogix_dp_device *dp)
> >   {
> >   	u32 reg;
> >   
> > -	if (dp->hpd_gpiod)
> > +	if (dp->hpd_gpiod || dp->hpd_bridge)
> >   		return;
> >   
> >   	analogix_dp_clear_hotplug_interrupts(dp, HPD_IRQ);
> > @@ -539,6 +539,9 @@ int analogix_dp_get_plug_in_status(struct analogix_dp_device *dp)
> >   	if (dp->hpd_gpiod) {
> >   		if (gpiod_get_value(dp->hpd_gpiod))
> >   			return 0;
> > +	} else if (dp->hpd_bridge) {
> > +		if (dp->connection_notified)
> > +			return 0;
> >   	} else {
> >   		reg = readl(dp->reg_base + ANALOGIX_DP_SYS_CTL_3);
> >   		if (reg & HPD_STATUS)
> > 
> > 
> > 
> > 
> > 
> 
>