linux-kernel - Re: [PATCH] drm/bridge: parade-ps8640: Fix additional suspend/resume at bootup

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Date:   Wed, 17 Nov 2021 08:50:36 -0800
From:   Doug Anderson <dianders@...gle.com>
To:     yangcong <yangcong5@...qin.corp-partner.google.com>
Cc:     swboyd@...omium.org, robert.foss@...aro.org,
        narmstrong@...libre.com, laurent.pinchart@...asonboard.com,
        jonas@...boo.se, jernej.skrabec@...il.com, airlied@...ux.ie,
        daniel@...ll.ch, a.hajda@...sung.com, philipchen@...omium.org,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/bridge: parade-ps8640: Fix additional suspend/resume
 at bootup

Hi,

On Fri, Nov 12, 2021 at 8:32 AM Doug Anderson <dianders@...gle.com> wrote:
>
> Hi,
>
> On Fri, Nov 12, 2021 at 12:43 AM yangcong
> <yangcong5@...qin.corp-partner.google.com> wrote:
> >
> > Through log and waveform, we can see that there will be additional
> > suspend/resume when booting. This timing does not meet the ps8640 spec.
> > It seems that the delay of 500ms does not satisfied drm_panel_get_modes.
> > I increased it to 900ms and it seems that this problem can be solved.
> > To be safe, I'd just round up to a full 1000.
>
> Do be clear: I'm still not convinced that the old 500 ms actually
> causes any real problems. I think someone is just measuring with a
> scope and upset that they see the device power on and then power off
> again. In any case, if we can avoid an extra power cycle at boot then
> that seems sane to me. Since this is a tiny change, I'll plan to merge
> it some time next week unless someone yells.
>
> Reviewed-by: Douglas Anderson <dianders@...omium.org>

Pushed to drm-misc-next:

aa70a0996b0e drm/bridge: parade-ps8640: Fix additional suspend/resume at bootup