linux-kernel - Re: [PATCH] drm/amd/powerplay: work around enum conversion warnings

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Date:   Mon, 15 Jul 2019 11:20:48 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Rex Zhu <rex.zhu@....com>, Evan Quan <evan.quan@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Likun Gao <Likun.Gao@....com>,
        Huang Rui <ray.huang@....com>,
        Gui Chengming <Jack.Gui@....com>,
        Kevin Wang <kevin1.wang@....com>,
        Hawking Zhang <Hawking.Zhang@....com>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] drm/amd/powerplay: work around enum conversion warnings

On Mon, Jul 8, 2019 at 6:05 PM Arnd Bergmann <arnd@...db.de> wrote:
> On Mon, Jul 8, 2019 at 4:54 PM Nathan Chancellor
> <natechancellor@...il.com> wrote:

> > On Mon, Jul 08, 2019 at 03:57:06PM +0200, Arnd Bergmann wrote:
> > > A couple of calls to smu_get_current_clk_freq() and smu_force_clk_levels()
> > > pass constants of the wrong type, leading to warnings with clang-8:
> > >
> > > drivers/gpu/drm/amd/amdgpu/../powerplay/vega20_ppt.c:995:39: error: implicit conversion from enumeration type 'PPCLK_e' to different enumeration type 'enum smu_clk_type' [-Werror,-Wenum-conversion]
> > >                 ret = smu_get_current_clk_freq(smu, PPCLK_SOCCLK, &now);
> > >                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
> > > drivers/gpu/drm/amd/amdgpu/../powerplay/inc/amdgpu_smu.h:775:82: note: expanded from macro 'smu_get_current_clk_freq'
> > >         ((smu)->funcs->get_current_clk_freq? (smu)->funcs->get_current_clk_freq((smu), (clk_id), (value)) : 0)
> > >
> > > I could not figure out what the purpose is of mixing the types
> > > like this and if it is written like this intentionally.
> > > Assuming this is all correct, adding an explict case is an
> > > easy way to shut up the warnings.
> > >
> > > Fixes: bc0fcffd36ba ("drm/amd/powerplay: Unify smu handle task function (v2)")
> > > Fixes: 096761014227 ("drm/amd/powerplay: support sysfs to get socclk, fclk, dcefclk")
> > > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> >
> > I sent a series last week for all of the clang warnings that were added
> > in this driver recently.
> >
> > https://lore.kernel.org/lkml/20190704055217.45860-1-natechancellor@gmail.com/
> >
> > I think it is safe to use the CLK enums from the expected type (from
> > what I could see from going down the code flow rabbit hole).
> >
> > https://lore.kernel.org/lkml/20190704055217.45860-4-natechancellor@gmail.com/
> >
> > https://lore.kernel.org/lkml/20190704055217.45860-7-natechancellor@gmail.com/
>
> I tried that at first but concluded that it could not work because the constants
> are different. Either it's currently broken and you patches fix the runtime
> behavior, or it's currently correct and your patches break it.

d36893362d22 ("drm/amd/powerplay: fix smu clock type change miss error")
was now applied and contains the same change as your first patch.

I assume the other one is still needed though.

       Arnd