Re: [PATCH v1 0/7] Add HPD support for Rockchip Analogix DP

["Heiko Stübner" <heiko@sntech.de>]

Hi Damon,

Am Freitag, 31. Juli 2026, 11:55:42 Mitteleuropäische Sommerzeit schrieb Damon Ding:
> On 7/31/2026 5:23 PM, Heiko Stübner wrote:
> > Am Freitag, 31. Juli 2026, 05:08:45 Mitteleuropäische Sommerzeit schrieb Damon Ding:
> >> On 7/31/2026 2:49 AM, Heiko Stübner wrote:
> >>> Am Donnerstag, 30. Juli 2026, 05:27:37 Mitteleuropäische Sommerzeit schrieb Damon Ding:
> >>>> This series improves the HPD (Hotplug Detect) interrupt handling in
> >>>> the Analogix DP driver to enable reliable native HPD pin detection on
> >>>> Rockchip platforms, and introduces platform-specific HPD detection
> >>>> schemes with fine-grained interrupt control.
> >>>
> >>> [...]
> >>>
> >>>> Tested on RK3576 with both native HPD pin and GPIO HPD configurations.
> >>>>
> >>>> Native HPD pin mode:
> >>>>
> >>>>     &edp {
> >>>>         status = "okay";
> >>>>         pinctrl-names = "default";
> >>>>         pinctrl-0 = <&edp_txm0_pins>;
> >>>>     };
> >>>>
> >>>> GPIO HPD mode:
> >>>>
> >>>>     &edp {
> >>>>         status = "okay";
> >>>>         pinctrl-names = "default";
> >>>>         pinctrl-0 = <&edp0_hpd>;
> >>>>         hpd-gpios = <&gpio4 RK_PC1 GPIO_ACTIVE_HIGH>;
> >>>>     };
> >>>>
> >>>>     &pinctrl {
> >>>>         edp {
> >>>>             edp0_hpd: edp0-hpd {
> >>>>                 rockchip,pins = <4 RK_PC1 0 &pcfg_pull_none>;
> >>>>             };
> >>>>         };
> >>>>     };
> >>>
> >>> Yay and thanks a lot for working on that.
> >>>
> >>> If I roll my display-port carrier board back to the analogix-dp being
> >>> the endpoint, this works exactly as expected :-) .
> >>>
> >>> I can plug in the display at some point after the boot and have it
> >>> detected and setup correctly. Same with unplugging it while
> >>> the system is running. The connection status is correctly reported
> >>> in sysfs.
> >>>
> >>>
> >>> Though there is a caveat. When the eDP is not the last part, this does not
> >>> work anymore. The detect function always returns "connected" if there is
> >>> a next bridge available.
> >>>
> >>> My board [0] has a physical DP connector on it, so models it as
> >>> dp-connector, but in that case the Analogix driver always reports being
> >>> connected.
> >>>
> >>>
> >>> [0] https://lore.kernel.org/linux-rockchip/20251009225050.88192-3-heiko@sntech.de/
> >>> ... same effect with hpd-gpios in either the edp node or dp-connector node
> >>>
> >>>
> >>
> >> My previous tests were carried out on the modified RK3576 IOTEST board
> >> DTS based on RK3576 EVB1, which includes dp-connector by default. I also
> >> did extra verification without dp-connector, and HPD detection works
> >> correctly in both cases.
> >>
> >> I've taken a look at the Tiger board DT configuration. The pinctrl
> >> settings for the eDP HPD GPIO may need adjustment:
> >>
> >> &pinctrl {
> >> 	edp0 {
> >> 		edp0_hpd_l: edp0-hpd-l-pin {
> >> 			rockchip,pins = <4 RK_PB5 RK_FUNC_GPIO &pcfg_pull_down>;
> >> 		};
> >> 	};
> >> };
> >>
> >> It is recommended to configure GPIO4B5 as pull-down or pll-none. Pull-up
> >> configuration may prevent GPIO interrupts from being triggered properly,
> >> resulting in a permanent "connected" status.
> > 
> > At least on that DP-carrier the pin direction is different.
> > I.e. it is active-low, meaning 0 for plugged in.
> > 
> > In the schematics I do see a hw pull up too - so pull-none in the pinconfig
> > would also be possible, but pull-down is definitly wrong on _this_ board.
> > 
> > So we're talking about the same code, I put the dts up on [0] .
> > 
> > I'm currently running with a printk diff [1] to showcase the issue.
> > 
> > So on boot, with the display unplugged I get:
> > [   14.757911] ---> drm_bridge_connector_detect: detect
> > [   14.757914] ---> analogix_dp_bridge_detect a
> > [   14.757918] ---> drm_bridge_connector_detect: detect
> > [   14.773779] ---> analogix_dp_bridge_detect a
> > [   14.838658] rockchip-dp fdec0000.edp: failed to read dpcd caps: -110
> > [   14.838662] [drm:analogix_dp_bridge_atomic_enable [analogix_dp]] *ERROR* dp commit error, ret = -110
> > [   14.838670] rockchip-dp fdec0000.edp: failed to set bridge, retry: 0
> > [   14.884791] rockchip-dp fdec0000.edp: failed to read dpcd caps: -110
> > [   14.884793] [drm:analogix_dp_bridge_atomic_enable [analogix_dp]] *ERROR* dp commit error, ret = -110
> > [   14.884796] rockchip-dp fdec0000.edp: failed to set bridge, retry: 1
> > [   14.930925] rockchip-dp fdec0000.edp: failed to read dpcd caps: -110
> > [   14.930927] [drm:analogix_dp_bridge_atomic_enable [analogix_dp]] *ERROR* dp commit error, ret = -110
> > [   14.930930] rockchip-dp fdec0000.edp: failed to set bridge, retry: 2
> > [   14.977032] rockchip-dp fdec0000.edp: failed to read dpcd caps: -110
> > [   14.977034] [drm:analogix_dp_bridge_atomic_enable [analogix_dp]] *ERROR* dp commit error, ret = -110
> > [   14.977037] rockchip-dp fdec0000.edp: failed to set bridge, retry: 3
> > [   15.023150] rockchip-dp fdec0000.edp: failed to read dpcd caps: -110
> > [   15.023152] [drm:analogix_dp_bridge_atomic_enable [analogix_dp]] *ERROR* dp commit error, ret = -110
> > [   15.023155] rockchip-dp fdec0000.edp: failed to set bridge, retry: 4
> > [   15.023168] rockchip-dp fdec0000.edp: too many times retry set bridge, give it up
> > [   15.052485] Console: switching to colour frame buffer device 80x30
> > [   15.210457] rockchip-drm display-subsystem: [drm] fb0: rockchipdrmfb frame buffer device
> > [   15.223444] ---> drm_bridge_connector_detect: detect
> > [   15.231974] ---> analogix_dp_bridge_detect a
> > [   15.239587] ---> drm_bridge_connector_detect: detect
> > [   15.245341] ---> analogix_dp_bridge_detect a
> > 
> > So analogix_dp_bridge_detect() is called and always returns connected.
> > 
> > Plugging in the the display, I get:
> > [  290.592096] ---> display_connector_detect gpio value is 1   {display-connector returning connected}
> > [  290.598648] ---> drm_bridge_connector_detect: detect
> > [  290.604637] ---> analogix_dp_bridge_detect a
> > [  290.609826] ---> drm_bridge_connector_detect: detect
> > [  290.615784] ---> analogix_dp_bridge_detect a
> > 
> > Unplugging the display, I get:
> > [  302.081444] ---> display_connector_detect gpio value is 0   {display-connector returning disconnected}
> > [  302.087996] ---> drm_bridge_connector_detect: detect
> > [  302.093945] ---> analogix_dp_bridge_detect a
> > [  302.099131] ---> drm_bridge_connector_detect: detect
> > [  302.105090] ---> analogix_dp_bridge_detect a
> > [  302.144834] ---> drm_bridge_connector_detect: detect
> > [  302.150784] ---> analogix_dp_bridge_detect a
> > [  302.155933] ---> drm_bridge_connector_detect: detect
> > [  302.161859] ---> analogix_dp_bridge_detect a
> > 
> > 
> > So it looks like on the gpio-side the detection is correct and/but
> > analogix_dp_bridge_detect() is always returning a connected state
> > ("b" output is never reached).
> > 
> > I'm still working on understanding how the whole detection logic works
> > in drm ;-) .
> > 
> > 
> 
> I think I've spotted the environmental difference between our setups.
> Your DTS places the hpd-gpios property under the dp-connector node,
> which is a scenario I haven't covered yet. I will reproduce and test 
> this case locally.
> 
> As a quick experiment, could you try removing hpd-gpios from 
> dp-connector and move it under the edp node instead? As expected, GPIO 
> HPD should work properly with that configuration.

I've updated the branch in [0] with that hpd move to the edp node, but
the result is similar:

With the panel _disconnected_ on boot I see
[   12.887555] ---> drm_bridge_connector_detect: detect
[   12.893104] ---> analogix_dp_bridge_detect a
[   12.897881] ---> drm_bridge_connector_detect: detect
[   12.903424] ---> analogix_dp_bridge_detect a
[   14.124848] [drm:analogix_dp_bridge_atomic_enable [analogix_dp]] *ERROR* failed to get hpd single ret = -110
[   14.124891] rockchip-dp fdec0000.edp: failed to set bridge, retry: 0
[   14.236031] [drm:analogix_dp_bridge_atomic_enable [analogix_dp]] *ERROR* failed to get hpd single ret = -110
[   14.236074] rockchip-dp fdec0000.edp: failed to set bridge, retry: 1
[   14.346940] [drm:analogix_dp_bridge_atomic_enable [analogix_dp]] *ERROR* failed to get hpd single ret = -110
[   14.346990] rockchip-dp fdec0000.edp: failed to set bridge, retry: 2
[   14.458590] [drm:analogix_dp_bridge_atomic_enable [analogix_dp]] *ERROR* failed to get hpd single ret = -110
[   14.458638] rockchip-dp fdec0000.edp: failed to set bridge, retry: 3
[   14.570262] [drm:analogix_dp_bridge_atomic_enable [analogix_dp]] *ERROR* failed to get hpd single ret = -110
[   14.570312] rockchip-dp fdec0000.edp: failed to set bridge, retry: 4
[   14.570328] rockchip-dp fdec0000.edp: too many times retry set bridge, give it up
[   14.751371] ---> drm_bridge_connector_detect: detect
[   14.757207] ---> analogix_dp_bridge_detect a

So with the diff from earlier, analogix_dp_bridge_detect() still runs,
finds its next bridge and returns "connected".

I.e. the
> >          if (dp->plat_data->next_bridge)
> >                  return connector_status_connected;

part.


Heiko



> > [0] https://github.com/mmind/linux-rockchip/blob/dev/v7.3/rk3588-tiger-dp-carrier-v5/arch/arm64/boot/dts/rockchip/rk3588-tiger-displayport-carrier.dts
> > [1]
> > diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > index 7a89548a7a885..0accdf62637ae 100644
> > --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > @@ -915,8 +915,10 @@ analogix_dp_bridge_detect(struct drm_bridge *bridge, struct drm_connector *conne
> >          struct analogix_dp_device *dp = to_dp(bridge);
> >          enum drm_connector_status status = connector_status_disconnected;
> >   
> > +printk("---> %s a\n", __func__);
> >          if (dp->plat_data->next_bridge)
> >                  return connector_status_connected;
> > +printk("---> %s b\n", __func__);
> >   
> >          if (!analogix_dp_detect_hpd(dp))
> >                  status = connector_status_connected;
> > diff --git a/drivers/gpu/drm/bridge/display-connector.c b/drivers/gpu/drm/bridge/display-connector.c
> > index 16c0631adeb18..b0c07694b82e3 100644
> > --- a/drivers/gpu/drm/bridge/display-connector.c
> > +++ b/drivers/gpu/drm/bridge/display-connector.c
> > @@ -45,6 +45,7 @@ static enum drm_connector_status display_connector_detect(struct drm_bridge *bri
> >          struct display_connector *conn = to_display_connector(bridge);
> >   
> >          if (conn->hpd_gpio) {
> > +printk("---> %s gpio value is %d\n", __func__, gpiod_get_value_cansleep(conn->hpd_gpio));
> >                  if (gpiod_get_value_cansleep(conn->hpd_gpio))
> >                          return connector_status_connected;
> >                  else
> > @@ -84,6 +85,7 @@ static enum drm_connector_status display_connector_detect(struct drm_bridge *bri
> >   static enum drm_connector_status
> >   display_connector_bridge_detect(struct drm_bridge *bridge, struct drm_connector *connector)
> >   {
> > +printk("---> %s\n", __func__);
> >          return display_connector_detect(bridge);
> >   }
> >   
> > diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
> > index 649969fca1413..8816d837c9a77 100644
> > --- a/drivers/gpu/drm/display/drm_bridge_connector.c
> > +++ b/drivers/gpu/drm/display/drm_bridge_connector.c
> > @@ -218,6 +218,7 @@ drm_bridge_connector_detect(struct drm_connector *connector, bool force)
> >          enum drm_connector_status status;
> >   
> >          if (detect) {
> > +printk("---> %s: detect\n", __func__);
> >                  status = detect->funcs->detect(detect, connector);
> >   
> >                  if (hdmi)
> > 
> > 
> > 
> > 
> > 
> 
>