linux-kernel - Re: [PATCH] omapdrm: dss: mark runtime PM functions __maybe

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Message-ID: <e3adce46-8eed-0af2-4aa3-9ac3bbf1508f@ideasonboard.com>
Date:   Wed, 8 Dec 2021 10:08:08 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Arnd Bergmann <arnd@...nel.org>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Cai Huoqing <caihuoqing@...du.com>,
        Arnd Bergmann <arnd@...db.de>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jyri Sarha <jsarha@...com>,
        Sebastian Reichel <sebastian.reichel@...labora.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] omapdrm: dss: mark runtime PM functions __maybe_unused

On 06/12/2021 13:14, Laurent Pinchart wrote:
> Hi Arnd,
> 
> Thank you for the patch.
> 
> On Sun, Dec 05, 2021 at 02:15:56PM +0100, Arnd Bergmann wrote:
>> From: Arnd Bergmann <arnd@...db.de>
>>
>> Using the SET_RUNTIME_PM_OPS() macro causes a warning about the
>> referenced functions when they are marked static but not __maybe_unused:
>>
>> drivers/gpu/drm/omapdrm/dss/dss.c:1572:12: error: unused function 'dss_runtime_suspend' [-Werror,-Wunused-function]
>> drivers/gpu/drm/omapdrm/dss/dss.c:1584:12: error: unused function 'dss_runtime_resume' [-Werror,-Wunused-function]
>> drivers/gpu/drm/omapdrm/dss/dispc.c:4845:12: error: unused function 'dispc_runtime_suspend' [-Werror,-Wunused-function]
>> drivers/gpu/drm/omapdrm/dss/dispc.c:4860:12: error: unused function 'dispc_runtime_resume' [-Werror,-Wunused-function]
>>
>> Fixes: b92f7ea556f8 ("drm/omap: dss: Make use of the helper macro SET_RUNTIME_PM_OPS()")
> 
> I wonder how well drivers are tested with !CONFIG_PM. We may be going
> through hoops and loops to support this when it actually won't work in
> most drivers. That's a separate issue though :-)

It won't work, but can be fixed. I did that for tidss, some years back. 
The problem is that the driver depends on runtime_suspend/resume to be 
called, and the fix is to call them manually when !CONFIG_PM.

> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> 
> Tomi, could you apply this ?

Yes, I'll push to drm-misc-next. Thanks!

  Tomi