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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YKwK+lkcHMwAosLn@pendragon.ideasonboard.com>
Date:   Mon, 24 May 2021 23:22:18 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Douglas Anderson <dianders@...omium.org>
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>, robdclark@...omium.org,
        David Airlie <airlied@...ux.ie>, linux-arm-msm@...r.kernel.org,
        Stephen Boyd <swboyd@...omium.org>,
        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>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 01/10] drm/panel: panel-simple: Add missing
 pm_runtime_dont_use_autosuspend() calls

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.

> 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>

> ---
> 
> Changes in v7:
> - pm_runtime_dont_use_autosuspend() fix new for v7.
> 
>  drivers/gpu/drm/panel/panel-simple.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
> index 9be050ab372f..21939d4352cf 100644
> --- a/drivers/gpu/drm/panel/panel-simple.c
> +++ b/drivers/gpu/drm/panel/panel-simple.c
> @@ -798,6 +798,7 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
>  	return 0;
>  
>  disable_pm_runtime:
> +	pm_runtime_dont_use_autosuspend(dev);
>  	pm_runtime_disable(dev);
>  free_ddc:
>  	if (panel->ddc)
> @@ -814,6 +815,7 @@ static int panel_simple_remove(struct device *dev)
>  	drm_panel_disable(&panel->base);
>  	drm_panel_unprepare(&panel->base);
>  
> +	pm_runtime_dont_use_autosuspend(dev);
>  	pm_runtime_disable(dev);
>  	if (panel->ddc)
>  		put_device(&panel->ddc->dev);

-- 
Regards,

Laurent Pinchart