linux-kernel - Re: [PATCH] drm/panel: boe-tv101wum-nl6: Ensure DSI writes succeed during disable

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Date:   Fri, 13 Jan 2023 14:49:43 -0600
From:   Stephen Boyd <swboyd@...omium.org>
To:     Sam Ravnborg <sam@...nborg.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        yangcong <yangcong5@...qin.corp-partner.google.com>,
        Douglas Anderson <dianders@...omium.org>,
        Jitao Shi <jitao.shi@...iatek.com>,
        Rob Clark <robdclark@...omium.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Subject: Re: [PATCH] drm/panel: boe-tv101wum-nl6: Ensure DSI writes succeed
 during disable

Quoting Sam Ravnborg (2023-01-13 06:52:09)
> Hi Stephen,
> On Tue, Jan 10, 2023 at 11:29:41AM -0800, Stephen Boyd wrote:
> > Quoting Sam Ravnborg (2023-01-07 12:28:41)
> >
> > >
> > > For this case we could ask ourself if the display needs to enter sleep
> > > mode right before we disable the regulator. But if the regulator is
> > > fixed, so the disable has no effect, this seems OK.
> >
> > What do you mean by fixed?
> What I tried to say here is if we have a fixed regulator - or in others
> words a supply voltage we cannot turn off, then entering sleep mode is
> important to reduce power consumption.
> But any sane design where power consumption is a concern will have the
> possibility to turn off the power anyway.

Ok got it!

>
> >
> > >
> > > Please fix the unprepare to not jump out early, on top of or together
> > > with the other fix.
> >
> > After this patch the unprepare only bails out early if the bool
> > 'prepared' flag isn't set.
> OK, then everything is fine.
>

Doug pointed out that enable isn't symmetric because it doesn't do the
DSI writes. I've updated the patch and I'll send a v2.