[PATCH v4 00/24] drm/bridge: Make panel and bridge probe order consistent

[John Stultz]

On Fri, Sep 10, 2021 at 3:12 AM Maxime Ripard <maxime at cerno.tech> wrote:
>
> We've encountered an issue with the RaspberryPi DSI panel that prevented the
> whole display driver from probing.
>
> The issue is described in detail in the commit 7213246a803f ("drm/vc4: dsi:
> Only register our component once a DSI device is attached"), but the basic idea
> is that since the panel is probed through i2c, there's no synchronization
> between its probe and the registration of the MIPI-DSI host it's attached to.
>
> We initially moved the component framework registration to the MIPI-DSI Host
> attach hook to make sure we register our component only when we have a DSI
> device attached to our MIPI-DSI host, and then use lookup our DSI device in our
> bind hook.
>
> However, all the DSI bridges controlled through i2c are only registering their
> associated DSI device in their bridge attach hook, meaning with our change
> above, we never got that far, and therefore ended up in the same situation than
> the one we were trying to fix for panels.
>
> The best practice to avoid those issues is to register its functions only after
> all its dependencies are live. We also shouldn't wait any longer than we should
> to play nice with the other components that are waiting for us, so in our case
> that would mean moving the DSI device registration to the bridge probe.
>
> I also had a look at all the DSI hosts, and it seems that exynos, kirin and msm
> would be affected by this and wouldn't probe anymore after those changes.
> Exynos and kirin seems to be simple enough for a mechanical change (that still
> requires to be tested), but the changes in msm seemed to be far more important
> and I wasn't confortable doing them.


Hey Maxime,
  Sorry for taking so long to get to this, but now that plumbers is
over I've had a chance to check it out on kirin

Rob Clark pointed me to his branch with some fixups here:
   https://gitlab.freedesktop.org/robclark/msm/-/commits/for-mripard/bridge-rework

But trying to boot hikey with that, I see the following loop indefinitely:
[    4.632132] adv7511 2-0039: supply avdd not found, using dummy regulator
[    4.638961] adv7511 2-0039: supply dvdd not found, using dummy regulator
[    4.645741] adv7511 2-0039: supply pvdd not found, using dummy regulator
[    4.652483] adv7511 2-0039: supply a2vdd not found, using dummy regulator
[    4.659342] adv7511 2-0039: supply v3p3 not found, using dummy regulator
[    4.666086] adv7511 2-0039: supply v1p2 not found, using dummy regulator
[    4.681898] adv7511 2-0039: failed to find dsi host
[    4.688836] adv7511 2-0039: supply avdd not found, using dummy regulator
[    4.695724] adv7511 2-0039: supply dvdd not found, using dummy regulator
[    4.702583] adv7511 2-0039: supply pvdd not found, using dummy regulator
[    4.709369] adv7511 2-0039: supply a2vdd not found, using dummy regulator
[    4.716232] adv7511 2-0039: supply v3p3 not found, using dummy regulator
[    4.722972] adv7511 2-0039: supply v1p2 not found, using dummy regulator
[    4.738720] adv7511 2-0039: failed to find dsi host

I'll have to dig a bit to figure out what's going wrong, but wanted to
give you the heads up that there seems to be a problem

thanks
-john