Re: [PATCH 04/10] drm/bridge: Document the probe issue with MIPI-DSI bridges

Maxime Ripard
2021-07-26T15:17:04Z

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Hi Daniel,

On Wed, Jul 21, 2021 at 02:05:01PM +0200, Daniel Vetter wrote:
> On Tue, Jul 20, 2021 at 03:45:19PM +0200, Maxime Ripard wrote:
> > Interactions between bridges, panels, MIPI-DSI host and the component
> > framework are not trivial and can lead to probing issues when
> > implementing a display driver. Let's document the various cases we need
> > too consider, and the solution to support all the cases.
> >
> > Signed-off-by: Maxime Ripard <maxime@cerno.tech>
>
> I still have this dream that eventually we resurrect a patch to add
> device_link to bridges/panels (ideally automatically), to help with some
> of the suspend/resume issues around here.
>
> Will this make things worse?
>
> I think it'd be really good to figure that out with some coding, since if
> we have incompatible solution to handle probe issues vs suspend/resume
> issues, we're screwed.
>
> Atm the duct-tape is to carefully move things around between suspend and
> suspend_early hooks (and resume and resume_late) and hope it all works ...

My initial idea to fix this was indeed to use device links. I gave up
after a while since it doesn't look like there's a way to add a device
link before either the bridge or encoder probes.

Indeed the OF-Graph representation is device-specific, so it can't be
generic, and if you need to probe to add that link, well, it's already
too late for the probe ordering :)

Maxime

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