linux-kernel - Re: [PATCH] drm/amdgpu: Initialize shadow to false in gfx_v9_0_rlcg

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Message-ID: <CAKwvOd=AA8NrqmOR=E7+e6dHEVo3DZwfSuK72DGzHG+X56pB7A@mail.gmail.com>
Date:   Wed, 18 Mar 2020 13:43:54 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Joe Perches <joe@...ches.com>
Cc:     Nathan Chancellor <natechancellor@...il.com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] drm/amdgpu: Initialize shadow to false in gfx_v9_0_rlcg_wreg

On Wed, Mar 18, 2020 at 1:28 PM Joe Perches <joe@...ches.com> wrote:
>
> On Tue, 2020-03-17 at 17:25 -0700, Nathan Chancellor wrote:
> > clang warns:
> >
> > drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:754:6: warning: variable 'shadow'
> > is used uninitialized whenever 'if' condition is
> > false [-Wsometimes-uninitialized]
> >         if (offset == grbm_cntl || offset == grbm_idx)
> >             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c:757:6: note: uninitialized use
> > occurs here
> >         if (shadow) {
> >             ^~~~~~
>
> Wouldn't it be better to get rid of the shadow variable completely?

Yes, much better indeed. Seems it only has one use.

> ---
>  drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> index 7bc248..496b9e 100644
> --- a/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/gfx_v9_0.c
> @@ -735,7 +735,6 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)
>         static void *spare_int;
>         static uint32_t grbm_cntl;
>         static uint32_t grbm_idx;
> -       bool shadow;
>
>         scratch_reg0 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG0_BASE_IDX] + mmSCRATCH_REG0)*4;
>         scratch_reg1 = adev->rmmio + (adev->reg_offset[GC_HWIP][0][mmSCRATCH_REG1_BASE_IDX] + mmSCRATCH_REG1)*4;
> @@ -751,10 +750,7 @@ void gfx_v9_0_rlcg_wreg(struct amdgpu_device *adev, u32 offset, u32 v)
>                 return;
>         }
>
> -       if (offset == grbm_cntl || offset == grbm_idx)
> -               shadow = true;
> -
> -       if (shadow) {
> +       if (offset == grbm_cntl || offset == grbm_idx) {
>                 if (offset  == grbm_cntl)
>                         writel(v, scratch_reg2);
>                 else if (offset == grbm_idx)
>
>
> --
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-- 
Thanks,
~Nick Desaulniers