On Thu, Oct 09, 2025 at 09:30:28PM +0200, Heiko Stuebner wrote:
> Right now if there is a next bridge attached to the analogix-dp controller
> the driver always assumes this bridge is connected to something, but this
> is of course not always true, as that bridge could also be a hotpluggable
> dp port for example.
>
> On the other hand, as stated in commit cb640b2ca546 ("drm/bridge: display-
> connector: don't set OP_DETECT for DisplayPorts"), "Detecting the monitor
> for DisplayPort targets is more complicated than just reading the HPD pin
> level" and we should be "letting the actual DP driver perform detection."
>
> So use drm_bridge_detect() to detect the next bridge's state but ignore
> that bridge if the analogix-dp is handling the hpd-gpio.
>
> Signed-off-by: Heiko Stuebner <[email protected]>
> ---
> As this patch stands, it would go on top of v6 of Damon's bridge-connector
> work, but could very well be also integrated into one of the changes there.
>
> I don't know yet if my ordering and/or reasoning is the correct one or if
> a better handling could be done, but with that change I do get a nice
> hotplug behaviour on my rk3588-tiger-dp-carrier board, where the
> Analogix-DP ends in a full size DP port.
>
> drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> index c04b5829712b..cdc56e83b576 100644
> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> @@ -983,8 +983,12 @@ 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;
>
> - if (dp->plat_data->next_bridge)
> - return connector_status_connected;
> + /*
> + * An optional next bridge should be in charge of detection the
> + * connection status, except if we manage a actual hpd gpio.
> + */
> + if (dp->plat_data->next_bridge && !dp->hpd_gpiod)
> + return drm_bridge_detect(dp->plat_data->next_bridge, connector);
And it's also not correct because the next bridge might be a retimer
with the bridge next to it being a one with the actual detection
capabilities. drm_bridge_connector solves that in a much better way. See
the series at [1]
[1]
https://lore.kernel.org/dri-devel/[email protected]/
>
> if (!analogix_dp_detect_hpd(dp))
> status = connector_status_connected;
> --
> 2.47.2
>
--
With best wishes
Dmitry
