linux-kernel - Re: [PATCH v7 01/10] drm/panel: panel-simple: Add missing pm_runtime_dont_use

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Message-ID: <CAD=FV=VnJB_6PMo3FQt8djYDD7h0s=sc9TAbKLQMe-y+43Z3NQ@mail.gmail.com>
Date:   Mon, 24 May 2021 14:08:53 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Sam Ravnborg <sam@...nborg.org>,
        Rob Clark <robdclark@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stanislav Lisovskiy <stanislav.lisovskiy@...el.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Steev Klimaszewski <steev@...i.org>,
        Thierry Reding <treding@...dia.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 01/10] drm/panel: panel-simple: Add missing
 pm_runtime_dont_use_autosuspend() calls

Hi,

On Mon, May 24, 2021 at 1:22 PM Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Doug,
>
> Thank you for the patch.
>
> On Mon, May 17, 2021 at 01:08:58PM -0700, Douglas Anderson wrote:
> > The PM Runtime docs specifically call out the need to call
> > pm_runtime_dont_use_autosuspend() in the remove() callback if
> > pm_runtime_use_autosuspend() was called in probe():
> >
> > > Drivers in ->remove() callback should undo the runtime PM changes done
> > > in ->probe(). Usually this means calling pm_runtime_disable(),
> > > pm_runtime_dont_use_autosuspend() etc.
>
> ~/src/kernel/linux $ git grep pm_runtime_use_autosuspend -- drivers | wc -l
> 209
> ~/src/kernel/linux $ git grep pm_runtime_dont_use_autosuspend -- drivers | wc -l
> 80
>
> Seems like a lost battle :-(
>
> The fix is right, but I wonder if this shouldn't be handled
> automatically by the runtime PM core. The runtime PM API is notoriously
> difficult to use correctly.

No kidding.


> > We should do this. This fixes a warning splat that I saw when I was
> > testing out the panel-simple's remove().
> >
> > Fixes: 3235b0f20a0a ("drm/panel: panel-simple: Use runtime pm to avoid excessive unprepare / prepare")
> > Signed-off-by: Douglas Anderson <dianders@...omium.org>
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

Thanks! I have pushed just this patch for now.

-Doug