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

["Heiko Stübner" <heiko@sntech.de>]

Hi Damon,

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 ;-) .


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)