DSI Bridge switching

[Andrzej Hajda]

Hi,

Removed my invalid email (I will update files next week).


On 08.10.2021 13:14, Jagan Teki wrote:
> Hi,
> 
> I think this seems to be a known use case for industrial these days with i.mx8m.
> 
> The host DSI would configure with two bridges one for DSI to LVDS
> (SN65DSI83) and another for DSI to HDMI Out (ADV7535). Technically we
> can use only one bridge at a time as host DSI support single out port.
> So we can have two separate device tree files for LVDS and HDMI and
> load them static.
> 
> But, one of the use cases is to support both of them in single dts, and
> - Turn On LVDS (default)
> - Turn Off LVDS then Turn On HDMI when cable plug-in

Are you sure it will work from hardware PoV? Do you have some demuxer? 
isolation of pins?

> 
> The HDMI event can be detected via some HDMI-INT GPIO on-board design.
> 
> The possible solution, I'm thinking of adding LVDS on port 1, HDMI on
> port 2 in the DSI host node, and trying to attach the respective
> bridge based on HDMI-INT like repeating the bridge attachment cycle
> based on the HDMI-INT.

I think more appropriate would be to share the same port, but provide 
two endpoints inside this port - we have two hardware sharing the same 
physical port.

> 
> Can it be possible to do bridge attachment at runtime? something like
> a bridge hotplug event? or any other possible solutions?
> 
> Any suggestions?

Practically it is possible, see exynos_dsi + panels, or exynos_dsi + 
some toshiba bridge - panel and bridge are dynamically 'plugged' and 
'unplugged' from exynos_drm, but they do not use bridge chain for this 
and some other reasons. (un|re|)plugging should be performed of course 
when pipeline is off (connector disconnected). I am not sure about 
bridges added to bridge chain - you need to inspect all opses to ensure 
it can be done safely.

And the main issue: Daniel does not like it :)

Regards
Andrzej


> 
> Thanks,
> Jagan.
>