DRM Master ignoring hotplug event during display switching (QT)

[Jagan Teki]

Hi all,

I have implemented runtime display switching in the MIPI switch design
where LVDS and HDMI bridges are selected with the help of runtime
GPIO.

Initial discussion on the same can be found here,
https://www.spinics.net/lists/dri-devel/msg318524.html

The implementation has been done by creating each connector at
runtime. The default boot will create the LVDS connector and based on
the HDMI plug-in the ISR.

1. forcing the LVDS to disconnect
2. call drm_kms_helper_hotplug_event
3. detach the bridge chain
4. attach the new bridge chain (HDMI)
5. call drm_kms_helper_hotplug_event

do the reverse when we unplug the HDMI cable.

So, the bridge chains are attached and detached based on GPIO
Interrupt which is indeed identified based on the physical HDMIA
connector.

Pipeline for LVDS,
mxfsb => nwl-dsi => display-switch => sn65dsi83=> panel-bridge

Pipeline for HDMI,
mxfsb => nwl-dsi => display-switch => adv7511 => display-connector

With this, implementation and I can able switch the displays with
default DRM (without specific DRM applications) where the LVDS is ON
by default and when HDMI plug-in the LVDS OFF/HDMI ON, and when HDMI
unplug the HDMI OFF/LVDS ON.

However, with QT5 I can see the DRM Master ignoring hotplug event by
returning 0 on drm_master_internal_acquire in
drm_fb_helper_hotplug_event. With this the hotplug returned early so
it cannot able to disconnect and connect the new switching connector.

Any help?

Thanks,
Jagan.