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Date: Mon, 15 Aug 2022 15:17:57 +0000 From: "Dong, Ruijing" <Ruijing.Dong@....com> To: Khalid Masum <khalid.masum.92@...il.com>, "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>, "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-kernel-mentees@...ts.linuxfoundation.org" <linux-kernel-mentees@...ts.linuxfoundation.org> CC: "Deucher, Alexander" <Alexander.Deucher@....com>, "Koenig, Christian" <Christian.Koenig@....com>, "Pan, Xinhui" <Xinhui.Pan@....com>, David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>, "Zhu, James" <James.Zhu@....com>, "Jiang, Sonny" <Sonny.Jiang@....com>, Wan Jiabing <wanjiabing@...o.com>, "Liu, Leo" <Leo.Liu@....com> Subject: RE: [PATCH linux-next] drm/amdgpu/vcn: Remove unused assignment in vcn_v4_0_stop [AMD Official Use Only - General] If the condition was met and it came to execute vcn_4_0_stop_dpg_mode, then it would never have a chance to go for /*wait for vcn idle*/, isn't it? I still didn't see obvious purpose of this change. if (adev->pg_flags & AMD_PG_SUPPORT_VCN_DPG) { ==> r = vcn_v4_0_stop_dpg_mode(adev, i); continue; } /* wait for vcn idle */ r = SOC15_WAIT_ON_RREG(VCN, i, regUVD_STATUS, UVD_STATUS__IDLE, 0x7); Thanks Ruijing -----Original Message----- From: Khalid Masum <khalid.masum.92@...il.com> Sent: Monday, August 15, 2022 11:11 AM To: Dong, Ruijing <Ruijing.Dong@....com>; amd-gfx@...ts.freedesktop.org; dri-devel@...ts.freedesktop.org; linux-kernel@...r.kernel.org; linux-kernel-mentees@...ts.linuxfoundation.org Cc: Deucher, Alexander <Alexander.Deucher@....com>; Koenig, Christian <Christian.Koenig@....com>; Pan, Xinhui <Xinhui.Pan@....com>; David Airlie <airlied@...ux.ie>; Daniel Vetter <daniel@...ll.ch>; Zhu, James <James.Zhu@....com>; Jiang, Sonny <Sonny.Jiang@....com>; Wan Jiabing <wanjiabing@...o.com>; Liu, Leo <Leo.Liu@....com> Subject: Re: [PATCH linux-next] drm/amdgpu/vcn: Remove unused assignment in vcn_v4_0_stop On 8/15/22 20:15, Dong, Ruijing wrote: > [AMD Official Use Only - General] > > Sorry, which "r" value was overwritten? I didn't see the point of making this change. > > Thanks > Ruijing > > -----Original Message----- > From: Khalid Masum <khalid.masum.92@...il.com> > Sent: Monday, August 15, 2022 3:01 AM > To: amd-gfx@...ts.freedesktop.org; dri-devel@...ts.freedesktop.org; > linux-kernel@...r.kernel.org; > linux-kernel-mentees@...ts.linuxfoundation.org > Cc: Deucher, Alexander <Alexander.Deucher@....com>; Koenig, Christian > <Christian.Koenig@....com>; Pan, Xinhui <Xinhui.Pan@....com>; David > Airlie <airlied@...ux.ie>; Daniel Vetter <daniel@...ll.ch>; Zhu, James > <James.Zhu@....com>; Jiang, Sonny <Sonny.Jiang@....com>; Dong, Ruijing > <Ruijing.Dong@....com>; Wan Jiabing <wanjiabing@...o.com>; Liu, Leo > <Leo.Liu@....com>; Khalid Masum <khalid.masum.92@...il.com> > Subject: [PATCH linux-next] drm/amdgpu/vcn: Remove unused assignment > in vcn_v4_0_stop > > The value assigned from vcn_v4_0_stop_dbg_mode to r is overwritten before it can be used. Remove this assignment. > > Addresses-Coverity: 1504988 ("Unused value") > Fixes: 8da1170a16e4 ("drm/amdgpu: add VCN4 ip block support") > Signed-off-by: Khalid Masum <khalid.masum.92@...il.com> > --- > drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c > b/drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c > index ca14c3ef742e..80b8a2c66b36 100644 > --- a/drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c > +++ b/drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c > @@ -1154,7 +1154,7 @@ static int vcn_v4_0_stop(struct amdgpu_device *adev) > fw_shared->sq.queue_mode |= FW_QUEUE_DPG_HOLD_OFF; > > if (adev->pg_flags & AMD_PG_SUPPORT_VCN_DPG) { > - r = vcn_v4_0_stop_dpg_mode(adev, i); > + vcn_v4_0_stop_dpg_mode(adev, i); > continue; > } > > -- > 2.37.1 > After value is overwritten soon right after the diff. See: drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c static int vcn_v4_0_stop(struct amdgpu_device *adev) { volatile struct amdgpu_vcn4_fw_shared *fw_shared; ... for (i = 0; i < adev->vcn.num_vcn_inst; ++i) { fw_shared = adev->vcn.inst[i].fw_shared.cpu_addr; fw_shared->sq.queue_mode |= FW_QUEUE_DPG_HOLD_OFF; if (adev->pg_flags & AMD_PG_SUPPORT_VCN_DPG) { r = vcn_v4_0_stop_dpg_mode(adev, i); continue; } /* wait for vcn idle */ r = SOC15_WAIT_ON_RREG(VCN, i, regUVD_STATUS, UVD_STATUS__IDLE, 0x7); Here, any value assigned to r is overwritten before it could be used. So the assignment in the true branch of the if statement here can be removed. Thanks, -- Khalid Masum
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