linux-kernel - Re: [PATCH] drm/tegra: mark t186 display hub PM functions __maybe

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Date:   Fri, 15 Dec 2017 14:33:40 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     David Airlie <airlied@...ux.ie>,
        Jonathan Hunter <jonathanh@...dia.com>,
        dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/tegra: mark t186 display hub PM functions
 __maybe_unused

On Fri, Dec 15, 2017 at 01:51:52PM +0100, Arnd Bergmann wrote:
> The newly introduced driver has optional suspend/resume functions,
> causing a warning when CONFIG_PM is disabled:
> 
> drivers/gpu/drm/tegra/hub.c:749:12: error: 'tegra_display_hub_resume' defined but not used [-Werror=unused-function]
> drivers/gpu/drm/tegra/hub.c:733:12: error: 'tegra_display_hub_suspend' defined but not used [-Werror=unused-function]
> 
> This marks them __maybe_unused to shut up the warnings.
> 
> Fixes: c4755fb9064f ("drm/tegra: Add Tegra186 display hub support")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/gpu/drm/tegra/hub.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

We had touched on this topic in a different thread. The Tegra DRM driver
currently relies on runtime PM to work properly. I don't see a reason to
not make that official by adding a select PM to menuconfig ARCH_TEGRA on
32-bit ARM just like we already do on 64-bit ARM.

I've gone and applied this patch as an interim solution. Once we've made
the switch to select PM on all generations of Tegra we can remove all
the #ifdef and __maybe_unused.

Thanks,
Thierry

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