[gpu-drm-radeon] question about potential dead code in vce_v2_0_enable_mgcg()

[gpu-drm-radeon] question about potential dead code in vce_v2_0_enable_mgcg()

[Gustavo A. R. Silva]

Hello everybody,

While looking into Coverity ID 1198635 I ran into the following piece  
of code at drivers/gpu/drm/radeon/vce_v2_0.c:107:

107void vce_v2_0_enable_mgcg(struct radeon_device *rdev, bool enable)
108{
109        bool sw_cg = false;
110
111        if (enable && (rdev->cg_flags & RADEON_CG_SUPPORT_VCE_MGCG)) {
112                if (sw_cg)
113                        vce_v2_0_set_sw_cg(rdev, true);
114                else
115                        vce_v2_0_set_dyn_cg(rdev, true);
116        } else {
117                vce_v2_0_disable_cg(rdev);
118
119                if (sw_cg)
120                        vce_v2_0_set_sw_cg(rdev, false);
121                else
122                        vce_v2_0_set_dyn_cg(rdev, false);
123        }
124}

The issue here is that local variable sw_cg is never updated again  
after its initialization; which cause some code to be logically dead.

My question here is if such variable is there for testing purposes or  
if it is a sort of an old code leftover that should be removed?

In any case I can send a patch to add a comment or remove the dead code.

I'd really appreciate any comments on this.

Thank you!
--
Gustavo A. R. Silva

RE: [gpu-drm-radeon] question about potential dead code in vce_v2_0_enable_mgcg()

[Deucher, Alexander]

> -----Original Message-----
> From: Gustavo A. R. Silva [mailto:garsilva@embeddedor.com]
> Sent: Wednesday, June 28, 2017 10:22 AM
> To: Deucher, Alexander; Koenig, Christian; David Airlie
> Cc: amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; linux-
> kernel@vger.kernel.org
> Subject: [gpu-drm-radeon] question about potential dead code in
> vce_v2_0_enable_mgcg()
> 
> 
> Hello everybody,
> 
> While looking into Coverity ID 1198635 I ran into the following piece
> of code at drivers/gpu/drm/radeon/vce_v2_0.c:107:
> 
> 107void vce_v2_0_enable_mgcg(struct radeon_device *rdev, bool enable)
> 108{
> 109        bool sw_cg = false;
> 110
> 111        if (enable && (rdev->cg_flags &
> RADEON_CG_SUPPORT_VCE_MGCG)) {
> 112                if (sw_cg)
> 113                        vce_v2_0_set_sw_cg(rdev, true);
> 114                else
> 115                        vce_v2_0_set_dyn_cg(rdev, true);
> 116        } else {
> 117                vce_v2_0_disable_cg(rdev);
> 118
> 119                if (sw_cg)
> 120                        vce_v2_0_set_sw_cg(rdev, false);
> 121                else
> 122                        vce_v2_0_set_dyn_cg(rdev, false);
> 123        }
> 124}
> 
> The issue here is that local variable sw_cg is never updated again
> after its initialization; which cause some code to be logically dead.
> 
> My question here is if such variable is there for testing purposes or
> if it is a sort of an old code leftover that should be removed?
> 
> In any case I can send a patch to add a comment or remove the dead code.
> 
> I'd really appreciate any comments on this.

I wanted to leave the code in for debugging if we ran into problems with dynamic clockgating.

Alex

Re: [gpu-drm-radeon] question about potential dead code in vce_v2_0_enable_mgcg()

[Gustavo A. R. Silva]

Hi Alex,

Quoting "Deucher, Alexander" <Alexander.Deucher@amd.com>:

>> -----Original Message-----
>> From: Gustavo A. R. Silva [mailto:garsilva@embeddedor.com]
>> Sent: Wednesday, June 28, 2017 10:22 AM
>> To: Deucher, Alexander; Koenig, Christian; David Airlie
>> Cc: amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; linux-
>> kernel@vger.kernel.org
>> Subject: [gpu-drm-radeon] question about potential dead code in
>> vce_v2_0_enable_mgcg()
>>
>>
>> Hello everybody,
>>
>> While looking into Coverity ID 1198635 I ran into the following piece
>> of code at drivers/gpu/drm/radeon/vce_v2_0.c:107:
>>
>> 107void vce_v2_0_enable_mgcg(struct radeon_device *rdev, bool enable)
>> 108{
>> 109        bool sw_cg = false;
>> 110
>> 111        if (enable && (rdev->cg_flags &
>> RADEON_CG_SUPPORT_VCE_MGCG)) {
>> 112                if (sw_cg)
>> 113                        vce_v2_0_set_sw_cg(rdev, true);
>> 114                else
>> 115                        vce_v2_0_set_dyn_cg(rdev, true);
>> 116        } else {
>> 117                vce_v2_0_disable_cg(rdev);
>> 118
>> 119                if (sw_cg)
>> 120                        vce_v2_0_set_sw_cg(rdev, false);
>> 121                else
>> 122                        vce_v2_0_set_dyn_cg(rdev, false);
>> 123        }
>> 124}
>>
>> The issue here is that local variable sw_cg is never updated again
>> after its initialization; which cause some code to be logically dead.
>>
>> My question here is if such variable is there for testing purposes or
>> if it is a sort of an old code leftover that should be removed?
>>
>> In any case I can send a patch to add a comment or remove the dead code.
>>
>> I'd really appreciate any comments on this.
>
> I wanted to leave the code in for debugging if we ran into problems  
> with dynamic clockgating.
>

Do you mind if I send a patch to add such comment and make it clear  
the purpose of that variable?

--- a/drivers/gpu/drm/radeon/vce_v2_0.c
+++ b/drivers/gpu/drm/radeon/vce_v2_0.c
@@ -104,6 +104,10 @@ static void vce_v2_0_disable_cg(struct  
radeon_device *rdev)
         WREG32(VCE_CGTT_CLK_OVERRIDE, 7);
  }

+/*
+ * Local variable sw_cg is used for debugging purposes, in case we
+ * ran into problems with dynamic clock gating. Don't remove it.
+ */
  void vce_v2_0_enable_mgcg(struct radeon_device *rdev, bool enable)
  {
         bool sw_cg = false;


Thanks for clarifying!
--
Gustavo A. R. Silva

Re: [gpu-drm-radeon] question about potential dead code in vce_v2_0_enable_mgcg()

[Alex Deucher]

On Wed, Jun 28, 2017 at 7:08 PM, Gustavo A. R. Silva
<garsilva@embeddedor.com> wrote:
> Hi Alex,
>
> Quoting "Deucher, Alexander" <Alexander.Deucher@amd.com>:
>
>>> -----Original Message-----
>>> From: Gustavo A. R. Silva [mailto:garsilva@embeddedor.com]
>>> Sent: Wednesday, June 28, 2017 10:22 AM
>>> To: Deucher, Alexander; Koenig, Christian; David Airlie
>>> Cc: amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org;
>>> linux-
>>> kernel@vger.kernel.org
>>> Subject: [gpu-drm-radeon] question about potential dead code in
>>> vce_v2_0_enable_mgcg()
>>>
>>>
>>> Hello everybody,
>>>
>>> While looking into Coverity ID 1198635 I ran into the following piece
>>> of code at drivers/gpu/drm/radeon/vce_v2_0.c:107:
>>>
>>> 107void vce_v2_0_enable_mgcg(struct radeon_device *rdev, bool enable)
>>> 108{
>>> 109        bool sw_cg = false;
>>> 110
>>> 111        if (enable && (rdev->cg_flags &
>>> RADEON_CG_SUPPORT_VCE_MGCG)) {
>>> 112                if (sw_cg)
>>> 113                        vce_v2_0_set_sw_cg(rdev, true);
>>> 114                else
>>> 115                        vce_v2_0_set_dyn_cg(rdev, true);
>>> 116        } else {
>>> 117                vce_v2_0_disable_cg(rdev);
>>> 118
>>> 119                if (sw_cg)
>>> 120                        vce_v2_0_set_sw_cg(rdev, false);
>>> 121                else
>>> 122                        vce_v2_0_set_dyn_cg(rdev, false);
>>> 123        }
>>> 124}
>>>
>>> The issue here is that local variable sw_cg is never updated again
>>> after its initialization; which cause some code to be logically dead.
>>>
>>> My question here is if such variable is there for testing purposes or
>>> if it is a sort of an old code leftover that should be removed?
>>>
>>> In any case I can send a patch to add a comment or remove the dead code.
>>>
>>> I'd really appreciate any comments on this.
>>
>>
>> I wanted to leave the code in for debugging if we ran into problems with
>> dynamic clockgating.
>>
>
> Do you mind if I send a patch to add such comment and make it clear the
> purpose of that variable?

Sure.  Thanks.

Alex

>
> --- a/drivers/gpu/drm/radeon/vce_v2_0.c
> +++ b/drivers/gpu/drm/radeon/vce_v2_0.c
> @@ -104,6 +104,10 @@ static void vce_v2_0_disable_cg(struct radeon_device
> *rdev)
>         WREG32(VCE_CGTT_CLK_OVERRIDE, 7);
>  }
>
> +/*
> + * Local variable sw_cg is used for debugging purposes, in case we
> + * ran into problems with dynamic clock gating. Don't remove it.
> + */
>  void vce_v2_0_enable_mgcg(struct radeon_device *rdev, bool enable)
>  {
>         bool sw_cg = false;
>
>
> Thanks for clarifying!
> --
> Gustavo A. R. Silva
>
>
>
>
>
>
> _______________________________________________
> amd-gfx mailing list
> amd-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx

[PATCH] drm/radeon: add header comment for clarification to vce_v2_0_enable_mgcg()

[Gustavo A. R. Silva]

Add function header comment to make it clear that local variable sw_cg
is used for debugging and it should not be removed.

Addresses-Coverity-ID: 1198635
Cc: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
---
 drivers/gpu/drm/radeon/vce_v2_0.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/radeon/vce_v2_0.c b/drivers/gpu/drm/radeon/vce_v2_0.c
index fce2144..b0a43b6 100644
--- a/drivers/gpu/drm/radeon/vce_v2_0.c
+++ b/drivers/gpu/drm/radeon/vce_v2_0.c
@@ -104,6 +104,10 @@ static void vce_v2_0_disable_cg(struct radeon_device *rdev)
 	WREG32(VCE_CGTT_CLK_OVERRIDE, 7);
 }
 
+/*
+ * Local variable sw_cg is used for debugging purposes, in case we
+ * ran into problems with dynamic clock gating. Don't remove it.
+ */
 void vce_v2_0_enable_mgcg(struct radeon_device *rdev, bool enable)
 {
 	bool sw_cg = false;
-- 
2.5.0

Re: [PATCH] drm/radeon: add header comment for clarification to vce_v2_0_enable_mgcg()

[Alex Deucher]

On Thu, Jun 29, 2017 at 1:38 PM, Gustavo A. R. Silva
<garsilva@embeddedor.com> wrote:
> Add function header comment to make it clear that local variable sw_cg
> is used for debugging and it should not be removed.
>
> Addresses-Coverity-ID: 1198635
> Cc: Alex Deucher <alexdeucher@gmail.com>
> Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>

Applied.  thanks!

Alex

> ---
>  drivers/gpu/drm/radeon/vce_v2_0.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/radeon/vce_v2_0.c b/drivers/gpu/drm/radeon/vce_v2_0.c
> index fce2144..b0a43b6 100644
> --- a/drivers/gpu/drm/radeon/vce_v2_0.c
> +++ b/drivers/gpu/drm/radeon/vce_v2_0.c
> @@ -104,6 +104,10 @@ static void vce_v2_0_disable_cg(struct radeon_device *rdev)
>         WREG32(VCE_CGTT_CLK_OVERRIDE, 7);
>  }
>
> +/*
> + * Local variable sw_cg is used for debugging purposes, in case we
> + * ran into problems with dynamic clock gating. Don't remove it.
> + */
>  void vce_v2_0_enable_mgcg(struct radeon_device *rdev, bool enable)
>  {
>         bool sw_cg = false;
> --
> 2.5.0
>

Re: [PATCH] drm/radeon: add header comment for clarification to vce_v2_0_enable_mgcg()

[Gustavo A. R. Silva]

Quoting Alex Deucher <alexdeucher@gmail.com>:

> On Thu, Jun 29, 2017 at 1:38 PM, Gustavo A. R. Silva
> <garsilva@embeddedor.com> wrote:
>> Add function header comment to make it clear that local variable sw_cg
>> is used for debugging and it should not be removed.
>>
>> Addresses-Coverity-ID: 1198635
>> Cc: Alex Deucher <alexdeucher@gmail.com>
>> Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
>
> Applied.  thanks!
>

Great, glad to help :)

Thanks
--
Gustavo A. R. Silva