[PATCH v1 0/7] Add HPD support for Rockchip Analogix DP
Heiko Stübner
heiko at sntech.de
Fri Jul 31 02:23:43 PDT 2026
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)
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