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:

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-----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

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