linux-kernel - Re: [PATCH 1/1] drm/amd/powerplay: initialize a variable before using it

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Date:   Sat, 4 Nov 2017 13:21:24 +0100
From:   Nicolas Iooss <nicolas.iooss_linux@....org>
To:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Airlie <airlied@...ux.ie>
Cc:     amd-gfx@...ts.freedesktop.org,
        ML dri-devel <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] drm/amd/powerplay: initialize a variable before using it

On Sun, Sep 3, 2017 at 2:00 PM, Nicolas Iooss
<nicolas.iooss_linux@....org> wrote:
>
> Function vega10_apply_state_adjust_rules() only initializes
> stable_pstate_sclk_dpm_percentage when
> data->registry_data.stable_pstate_sclk_dpm_percentage is not between 1
> and 100. The variable is then used to compute stable_pstate_sclk, which
> therefore uses an uninitialized value.
>
> Fix this by initializing stable_pstate_sclk_dpm_percentage to
> data->registry_data.stable_pstate_sclk_dpm_percentage.
>
> This issue has been found while building the kernel with clang. The
> compiler reported a -Wsometimes-uninitialized warning.
>
> Fixes: f83a9991648b ("drm/amd/powerplay: add Vega10 powerplay support (v5)")
> Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@....org>
> ---
>  drivers/gpu/drm/amd/powerplay/hwmgr/vega10_hwmgr.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/vega10_hwmgr.c b/drivers/gpu/drm/amd/powerplay/hwmgr/vega10_hwmgr.c
> index 197174e562d2..c8d28f78cd47 100644
> --- a/drivers/gpu/drm/amd/powerplay/hwmgr/vega10_hwmgr.c
> +++ b/drivers/gpu/drm/amd/powerplay/hwmgr/vega10_hwmgr.c
> @@ -3043,6 +3043,8 @@ static int vega10_apply_state_adjust_rules(struct pp_hwmgr *hwmgr,
>
>         if (phm_cap_enabled(hwmgr->platform_descriptor.platformCaps,
>                         PHM_PlatformCaps_StablePState)) {
> +               stable_pstate_sclk_dpm_percentage =
> +                       data->registry_data.stable_pstate_sclk_dpm_percentage;
>                 PP_ASSERT_WITH_CODE(
>                         data->registry_data.stable_pstate_sclk_dpm_percentage >= 1 &&
>                         data->registry_data.stable_pstate_sclk_dpm_percentage <= 100,
> --
> 2.14.1

Hello,
I have not received any comment on the above patch that I sent two
months ago, and the issue which is fixed by it still exists in today's
linux-next code [1]. Could you please review this patch?

Thanks,
Nicolas

[1] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/gpu/drm/amd/powerplay/hwmgr/vega10_hwmgr.c#n3137