Re: [PATCH linux-next] drm/amdgpu/vcn: Remove unused assignment in vcn_v4_0_stop

[Khalid Masum]

On 8/15/22 22:12, Greg KH wrote:
> On Mon, Aug 15, 2022 at 09:11:18PM +0600, Khalid Masum wrote:
> > 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@xxxxxxxxx>
> > > Sent: Monday, August 15, 2022 3:01 AM
> > > To: amd-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-kernel-mentees@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > Cc: Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Koenig, Christian <Christian.Koenig@xxxxxxx>; Pan, Xinhui <Xinhui.Pan@xxxxxxx>; David Airlie <airlied@xxxxxxxx>; Daniel Vetter <daniel@xxxxxxxx>; Zhu, James <James.Zhu@xxxxxxx>; Jiang, Sonny <Sonny.Jiang@xxxxxxx>; Dong, Ruijing <Ruijing.Dong@xxxxxxx>; Wan Jiabing <wanjiabing@xxxxxxxx>; Liu, Leo <Leo.Liu@xxxxxxx>; Khalid Masum <khalid.masum.92@xxxxxxxxx>
> > > 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@xxxxxxxxx>
> > > ---
> > >    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.
>
> Why not fix vcn_v4_0_stop_dpg_mode() to not return anything, as it does
> not, and then remove this assignment as well, which would fix up
> everything at once to be more obvious what is happening and why.

That makes sense. I shall send a v2 this way. Thanks for your suggestion.

> thanks,
>
> greg k-h

thanks,
  -- Khalid Masum