Re: [PATCH v7 01/10] drm/panel: panel-simple: Add missing pm_runtime_dont_use_autosuspend() calls

From: Doug Anderson <dianders@chromium.org>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Andrzej Hajda <a.hajda@samsung.com>,
	Neil Armstrong <narmstrong@baylibre.com>,
	Jonas Karlman <jonas@kwiboo.se>,
	Jernej Skrabec <jernej.skrabec@siol.net>,
	Sam Ravnborg <sam@ravnborg.org>,
	Rob Clark <robdclark@chromium.org>,
	David Airlie <airlied@linux.ie>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	Stephen Boyd <swboyd@chromium.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Steev Klimaszewski <steev@kali.org>,
	Thierry Reding <treding@nvidia.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v7 01/10] drm/panel: panel-simple: Add missing pm_runtime_dont_use_autosuspend() calls
Date: Mon, 24 May 2021 14:08:53 -0700	[thread overview]
Message-ID: <CAD=FV=VnJB_6PMo3FQt8djYDD7h0s=sc9TAbKLQMe-y+43Z3NQ@mail.gmail.com> (raw)
In-Reply-To: <YKwK+lkcHMwAosLn@pendragon.ideasonboard.com>

Hi,

On Mon, May 24, 2021 at 1:22 PM Laurent Pinchart
<laurent.pinchart@ideasonboard.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@chromium.org>
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Thanks! I have pushed just this patch for now.

-Doug