linux-kernel - Re: [PATCH] drm/bridge: fix anx6345 power up sequence

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Date:   Mon, 18 Apr 2022 17:25:57 -0700
From:   Vasily Khoruzhick <anarsoul@...il.com>
To:     Torsten Duwe <duwe@....de>
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Thierry Reding <treding@...dia.com>,
        Lyude Paul <lyude@...hat.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Harald Geyer <harald@...ib.org>, stable@...r.kernel.org
Subject: Re: [PATCH] drm/bridge: fix anx6345 power up sequence

On Sun, Apr 17, 2022 at 11:52 AM Vasily Khoruzhick <anarsoul@...il.com> wrote:
>
> On Sun, Apr 17, 2022 at 9:15 AM Torsten Duwe <duwe@....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.