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

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

[Khalid Masum]

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@gmail.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

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

[James Zhu via Linux-kernel-mentees]

[-- Attachment #1.1: Type: text/plain, Size: 1022 bytes --]

ThispatchisReviewed-by:JamesZhu<James.Zhu@amd.com>

On 2022-08-15 3:00 a.m., Khalid Masum wrote:
> 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@gmail.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;
>   		}
>   

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

[Dong, Ruijing via Linux-kernel-mentees]

[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@gmail.com>
Sent: Monday, August 15, 2022 3:01 AM
To: amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; linux-kernel@vger.kernel.org; linux-kernel-mentees@lists.linuxfoundation.org
Cc: Deucher, Alexander <Alexander.Deucher@amd.com>; Koenig, Christian <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David Airlie <airlied@linux.ie>; Daniel Vetter <daniel@ffwll.ch>; Zhu, James <James.Zhu@amd.com>; Jiang, Sonny <Sonny.Jiang@amd.com>; Dong, Ruijing <Ruijing.Dong@amd.com>; Wan Jiabing <wanjiabing@vivo.com>; Liu, Leo <Leo.Liu@amd.com>; Khalid Masum <khalid.masum.92@gmail.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@gmail.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

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

[Khalid Masum]

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@gmail.com>
> Sent: Monday, August 15, 2022 3:01 AM
> To: amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; linux-kernel@vger.kernel.org; linux-kernel-mentees@lists.linuxfoundation.org
> Cc: Deucher, Alexander <Alexander.Deucher@amd.com>; Koenig, Christian <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David Airlie <airlied@linux.ie>; Daniel Vetter <daniel@ffwll.ch>; Zhu, James <James.Zhu@amd.com>; Jiang, Sonny <Sonny.Jiang@amd.com>; Dong, Ruijing <Ruijing.Dong@amd.com>; Wan Jiabing <wanjiabing@vivo.com>; Liu, Leo <Leo.Liu@amd.com>; Khalid Masum <khalid.masum.92@gmail.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@gmail.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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RE: [PATCH linux-next] drm/amdgpu/vcn: Remove unused assignment in vcn_v4_0_stop

[Dong, Ruijing via Linux-kernel-mentees]

[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@gmail.com>
Sent: Monday, August 15, 2022 11:11 AM
To: Dong, Ruijing <Ruijing.Dong@amd.com>; amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; linux-kernel@vger.kernel.org; linux-kernel-mentees@lists.linuxfoundation.org
Cc: Deucher, Alexander <Alexander.Deucher@amd.com>; Koenig, Christian <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David Airlie <airlied@linux.ie>; Daniel Vetter <daniel@ffwll.ch>; Zhu, James <James.Zhu@amd.com>; Jiang, Sonny <Sonny.Jiang@amd.com>; Wan Jiabing <wanjiabing@vivo.com>; Liu, Leo <Leo.Liu@amd.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@gmail.com>
> Sent: Monday, August 15, 2022 3:01 AM
> To: amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org;
> linux-kernel@vger.kernel.org;
> linux-kernel-mentees@lists.linuxfoundation.org
> Cc: Deucher, Alexander <Alexander.Deucher@amd.com>; Koenig, Christian
> <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David
> Airlie <airlied@linux.ie>; Daniel Vetter <daniel@ffwll.ch>; Zhu, James
> <James.Zhu@amd.com>; Jiang, Sonny <Sonny.Jiang@amd.com>; Dong, Ruijing
> <Ruijing.Dong@amd.com>; Wan Jiabing <wanjiabing@vivo.com>; Liu, Leo
> <Leo.Liu@amd.com>; Khalid Masum <khalid.masum.92@gmail.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@gmail.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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Re: [PATCH linux-next] drm/amdgpu/vcn: Remove unused assignment in vcn_v4_0_stop

[Khalid Masum]

On 8/15/22 21:17, Dong, Ruijing wrote:
> [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?

Hypothetically, some other thread might set adev->pg_flags NULL and in 
that case it will get the chance to go for /* wait for vcn idle */.


> 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);

Regardless of that, this assignment to r is unnecessary. Because this 
value of r is never used. This patch simply removes this unnecessary
assignment.

>                           continue;
>                   }
> 
>                   /* wait for vcn idle */
>                   r = SOC15_WAIT_ON_RREG(VCN, i, regUVD_STATUS, UVD_STATUS__IDLE, 0x7);
> 
> Thanks
> Ruijing
> 

Thanks,
   -- Khalid Masum
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RE: [PATCH linux-next] drm/amdgpu/vcn: Remove unused assignment in vcn_v4_0_stop

[Dong, Ruijing via Linux-kernel-mentees]

[AMD Official Use Only - General]

Then please update commit message, this change is due to "value r is never used, and remove unnecessary assignment", that makes sense to me.

Thanks
Ruijing

-----Original Message-----
From: Khalid Masum <khalid.masum.92@gmail.com>
Sent: Monday, August 15, 2022 11:54 AM
To: Dong, Ruijing <Ruijing.Dong@amd.com>; amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; linux-kernel@vger.kernel.org; linux-kernel-mentees@lists.linuxfoundation.org
Cc: Deucher, Alexander <Alexander.Deucher@amd.com>; Koenig, Christian <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David Airlie <airlied@linux.ie>; Daniel Vetter <daniel@ffwll.ch>; Zhu, James <James.Zhu@amd.com>; Jiang, Sonny <Sonny.Jiang@amd.com>; Wan Jiabing <wanjiabing@vivo.com>; Liu, Leo <Leo.Liu@amd.com>
Subject: Re: [PATCH linux-next] drm/amdgpu/vcn: Remove unused assignment in vcn_v4_0_stop

On 8/15/22 21:17, Dong, Ruijing wrote:
> [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?

Hypothetically, some other thread might set adev->pg_flags NULL and in that case it will get the chance to go for /* wait for vcn idle */.


> 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);

Regardless of that, this assignment to r is unnecessary. Because this
value of r is never used. This patch simply removes this unnecessary
assignment.

>                           continue;
>                   }
>
>                   /* wait for vcn idle */
>                   r = SOC15_WAIT_ON_RREG(VCN, i, regUVD_STATUS, UVD_STATUS__IDLE, 0x7);
>
> Thanks
> Ruijing
>

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

[Khalid Masum]

On 8/15/22 22:00, Dong, Ruijing wrote:
> [AMD Official Use Only - General]
> 
> Then please update commit message, this change is due to "value r is never used, and remove unnecessary assignment", that makes sense to me.
> 
> Thanks
> Ruijing
> 
Greg also pointed out that the function vcn_v4_0_stop_dpg_mode should 
return void. I shall send a patch shortly with these two changes. Thanks 
for your suggestion.

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

[Greg KH]

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@gmail.com>
> > Sent: Monday, August 15, 2022 3:01 AM
> > To: amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; linux-kernel@vger.kernel.org; linux-kernel-mentees@lists.linuxfoundation.org
> > Cc: Deucher, Alexander <Alexander.Deucher@amd.com>; Koenig, Christian <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David Airlie <airlied@linux.ie>; Daniel Vetter <daniel@ffwll.ch>; Zhu, James <James.Zhu@amd.com>; Jiang, Sonny <Sonny.Jiang@amd.com>; Dong, Ruijing <Ruijing.Dong@amd.com>; Wan Jiabing <wanjiabing@vivo.com>; Liu, Leo <Leo.Liu@amd.com>; Khalid Masum <khalid.masum.92@gmail.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@gmail.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.

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.

thanks,

greg k-h
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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@gmail.com>
>>> Sent: Monday, August 15, 2022 3:01 AM
>>> To: amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; linux-kernel@vger.kernel.org; linux-kernel-mentees@lists.linuxfoundation.org
>>> Cc: Deucher, Alexander <Alexander.Deucher@amd.com>; Koenig, Christian <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David Airlie <airlied@linux.ie>; Daniel Vetter <daniel@ffwll.ch>; Zhu, James <James.Zhu@amd.com>; Jiang, Sonny <Sonny.Jiang@amd.com>; Dong, Ruijing <Ruijing.Dong@amd.com>; Wan Jiabing <wanjiabing@vivo.com>; Liu, Leo <Leo.Liu@amd.com>; Khalid Masum <khalid.masum.92@gmail.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@gmail.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.
> 
> 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

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