Hi Dmitry,
Am Freitag, 10. Oktober 2025, 00:30:11 Mitteleuropäische Sommerzeit schrieb
Dmitry Baryshkov:
> 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]/
Hence my comment above about that possibly not being the right variant.
Sort of asking for direction :-) .
I am working on top of Damon's drm-bridge-connector series as noted above,
but it looks like the detect function still is called at does then stuff.
My board is the rk3588-tiger-displayport-carrier [0], with a dp-connector
which is the next bridge, so _without_ any changes, the analogix-dp
always assumes "something" is connected and I end up with
[ 9.869198] [drm:analogix_dp_bridge_atomic_enable] *ERROR* failed to get hpd
single ret = -110
[ 9.980422] [drm:analogix_dp_bridge_atomic_enable] *ERROR* failed to get hpd
single ret = -110
[ 10.091522] [drm:analogix_dp_bridge_atomic_enable] *ERROR* failed to get hpd
single ret = -110
[ 10.202419] [drm:analogix_dp_bridge_atomic_enable] *ERROR* failed to get hpd
single ret = -110
[ 10.313651] [drm:analogix_dp_bridge_atomic_enable] *ERROR* failed to get hpd
single ret = -110
when no display is connected.
With this change I do get the expected hotplug behaviour, so something is
missing still even with the bridge-connector series.
Heiko
[0] v3: https://lore.kernel.org/r/[email protected]
v4: https://lore.kernel.org/r/[email protected]
(moved hpd-gpios from dp-connector back to analogix-dp per dp-connector
being not able to detect dp-monitors)
>
> >
> > if (!analogix_dp_detect_hpd(dp))
> > status = connector_status_connected;
>
>
