[PATCH] drm/bridge: fix anx6345 power up sequence

[Vasily Khoruzhick]

On Sun, Apr 17, 2022 at 11:52 AM Vasily Khoruzhick <anarsoul at gmail.com> wrote:
>
> On Sun, Apr 17, 2022 at 9:15 AM Torsten Duwe <duwe at lst.de> wrote:
> >
> > Align the power-up sequence with the known-good procedure documented in [1]:
> > un-swap dvdd12 and dvdd25, and allow a little extra time for them to settle
> > before de-asserting reset.
>
> Hi Torsten,
>
> Interesting find! I tried to fix the issue several times by playing
> with the delays to no avail.
>
> What's interesting, ANX6345 datasheet allows DVDD12 to come up either
> earlier or later than DVDD25 with the delay of T1 (2ms typical)
> between them, and actually bringing up DVDD12 first works fine in
> u-boot.
>
> The datasheet also requires reset to be deasserted no earlier than T2
> (2-5ms) after all the rails are stable.
>
> Another thing it mentions is that the system clock must be stable for
> T3 (1-3ms) before reset is deasserted, T3 is already a part of T2,
> however it cannot be gated on Pinebook, see [1], page 15
>
> The change looks good to me, but I'll need some time to actually test
> it. If you don't hear from me for longer than a week please ping me.

Your change doesn't fix the issue for me. Running "xrandr --output
eDP-1 --off; xrandr --output eDP-1 --auto" in a loop triggers the
issue pretty quickly even with the patch.