linux-kernel - Re: [PATCH] drm/amdgpu: fix structurally dead code vcn_v2_5_hw

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Message-ID: <dc76a52b-09a2-7ab9-b53e-52500f4f8669@amd.com>
Date:   Tue, 1 Oct 2019 21:46:26 +0000
From:   "Liu, Leo" <Leo.Liu@....com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "Zhou, David(ChunMing)" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
CC:     "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/amdgpu: fix structurally dead code vcn_v2_5_hw_init


On 2019-10-01 5:43 p.m., Gustavo A. R. Silva wrote:
> Hi,
>
> On 10/1/19 16:29, Liu, Leo wrote:
>> On 2019-10-01 1:16 p.m., Gustavo A. R. Silva wrote:
>>> Notice that there is a *continue* statement in the middle of the
>>> for loop and that prevents the code below from ever being reached:
>>>
>>> 	r = amdgpu_ring_test_ring(ring);
>>> 	if (r) {
>>> 		ring->sched.ready = false;
>>> 		goto done;
>>> 	}
>>>
>>> Fix this by removing the continue statement and updating ring->sched.ready
>>> to true before calling amdgpu_ring_test_ring(ring).
>>>
>>> Notice that this fix is based on
>>> commit 1b61de45dfaf ("drm/amdgpu: add initial VCN2.0 support (v2)")
>>>
>>> Addresses-Coverity-ID 1485608 ("Structurally dead code")
>>> Fixes: 28c17d72072b ("drm/amdgpu: add VCN2.5 basic supports")
>>> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
>>> ---
>>>
>>> Any feedback is greatly appreciated.
>>>
>>>    drivers/gpu/drm/amd/amdgpu/vcn_v2_5.c | 5 +++--
>>>    1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v2_5.c b/drivers/gpu/drm/amd/amdgpu/vcn_v2_5.c
>>> index 395c2259f979..47b0dcd59e13 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/vcn_v2_5.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/vcn_v2_5.c
>>> @@ -258,6 +258,7 @@ static int vcn_v2_5_hw_init(void *handle)
>>>    		adev->nbio_funcs->vcn_doorbell_range(adev, ring->use_doorbell,
>>>    						     ring->doorbell_index, j);
>>>    
>>> +		ring->sched.ready = true;
>> This is redundant. all the sched->ready is initialized as true, please
>> refer to drm_sched_init()
>>
> I see... so in the following commit 1b61de45dfaf ("drm/amdgpu: add initial VCN2.0 support (v2)")
> that line is also redundant?

Yes.


>>>    		r = amdgpu_ring_test_ring(ring);
>>>    		if (r) {
>>>    			ring->sched.ready = false;
>>> @@ -266,8 +267,7 @@ static int vcn_v2_5_hw_init(void *handle)
>>>    
>>>    		for (i = 0; i < adev->vcn.num_enc_rings; ++i) {
>>>    			ring = &adev->vcn.inst[j].ring_enc[i];
>>> -			ring->sched.ready = false;
>>> -			continue;
>>> +			ring->sched.ready = true;
>> Because the VCN 2.5 FW still has issue for encode, so we have it
>> disabled here.
>>
> OK. So, maybe we can add a comment pointing that out?

That could be better.

Thanks,
Leo


>
> Thanks
> --
> Gustavo
>
>>>    			r = amdgpu_ring_test_ring(ring);
>>>    			if (r) {
>>>    				ring->sched.ready = false;
>>> @@ -276,6 +276,7 @@ static int vcn_v2_5_hw_init(void *handle)
>>>    		}
>>>    
>>>    		ring = &adev->vcn.inst[j].ring_jpeg;
>>> +		ring->sched.ready = true;
>>>    		r = amdgpu_ring_test_ring(ring);
>>>    		if (r) {
>>>    			ring->sched.ready = false;