linux-kernel - Re: [PATCH][next] drm/amdgpu: remove redundant assignment to pointer 'ring'

Open Source and information security mailing list archives

Message-ID: <CADnq5_PE1rDzqd13MPWJmeK_BUS0EthH=WcZ0wruTy55yarnpw@mail.gmail.com>
Date:   Tue, 23 Jul 2019 14:45:07 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Zhou <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Leo Liu <leo.liu@....com>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>, kernel-janitors@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][next] drm/amdgpu: remove redundant assignment to pointer 'ring'

On Tue, Jul 23, 2019 at 9:41 AM Colin King <colin.king@...onical.com> wrote:
>
> From: Colin Ian King <colin.king@...onical.com>
>
> The pointer 'ring' is being assigned a value that is never
> read, hence the assignment is redundant and can be removed.
>
> Addresses-Coverity: ("Unused value")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c b/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
> index 93b3500e522b..a2a8ca942f34 100644
> --- a/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
> +++ b/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
> @@ -1331,7 +1331,6 @@ static int vcn_v1_0_pause_dpg_mode(struct amdgpu_device *adev,
>                                 WREG32_SOC15(UVD, 0, mmUVD_JRBC_RB_CNTL,
>                                                         UVD_JRBC_RB_CNTL__RB_RPTR_WR_EN_MASK);
>
> -                               ring = &adev->vcn.inst->ring_dec;
>                                 WREG32_SOC15(UVD, 0, mmUVD_RBC_RB_WPTR,
>                                                    RREG32_SOC15(UVD, 0, mmUVD_SCRATCH2) & 0x7FFFFFFF);
>                                 SOC15_WAIT_ON_RREG(UVD, 0, mmUVD_POWER_STATUS,

While we don't use ring here, I think the assignment is useful to
delineate that we are no longer working with the jpeg ring, but rather
the decode ring.  The mmUVD_RBC_RB_WPTR register is part of the decode
ring, not jpeg.  We would normally use the ring->wptr like we do for
the other rings, but in this particular case, the value happens to be
shadowed to a scratch register due to the way the dynamic power gating
works on that ring.

Alex

> --
> 2.20.1
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives