From: "Gustavo A. R. Silva" <garsilva@embeddedor.com>
To: "Deucher, Alexander" <Alexander.Deucher@amd.com>
Cc: "Koenig, Christian" <Christian.Koenig@amd.com>,
David Airlie <airlied@linux.ie>,
amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
linux-kernel@vger.kernel.org
Subject: Re: [gpu-drm-radeon] question about potential dead code in vce_v2_0_enable_mgcg()
Date: Wed, 28 Jun 2017 18:08:43 -0500 [thread overview]
Message-ID: <20170628180843.Horde.KKnryIaN7wki5B896j1w8Sa@gator4166.hostgator.com> (raw)
In-Reply-To: <BN6PR12MB1652D3DE81BA07C8634AF5D5F7DD0@BN6PR12MB1652.namprd12.prod.outlook.com>
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
next prev parent reply other threads:[~2017-06-28 23:08 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-28 14:22 [gpu-drm-radeon] question about potential dead code in vce_v2_0_enable_mgcg() Gustavo A. R. Silva
2017-06-28 15:40 ` Deucher, Alexander
2017-06-28 15:40 ` Deucher, Alexander
2017-06-28 23:08 ` Gustavo A. R. Silva [this message]
2017-06-29 12:34 ` Alex Deucher
2017-06-29 12:34 ` Alex Deucher
2017-06-29 17:38 ` [PATCH] drm/radeon: add header comment for clarification to vce_v2_0_enable_mgcg() Gustavo A. R. Silva
2017-06-29 19:25 ` Alex Deucher
2017-06-29 19:25 ` Alex Deucher
2017-06-29 19:52 ` Gustavo A. R. Silva
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