Re: [PATCH] drm/amdgpu: fix ring test failure issue during s3 in vce 3.0

["Liu, Leo" <Leo.Liu-5C7GfCeVMHo@public.gmane.org>]

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int amdgpu_vce_ring_test_ring(struct amdgpu_ring *ring)
{
    struct amdgpu_device *adev = ring->adev;

    uint32_t rptr = amdgpu_ring_get_rptr(ring);

    unsigned i;
    int r, timeout = adev->usec_timeout;

    /* skip ring test for sriov*/
    if (amdgpu_sriov_vf(adev))
        return 0;

    r = amdgpu_ring_alloc(ring, 16);
    if (r)
        return r;

    amdgpu_ring_write(ring, VCE_CMD_END);
    amdgpu_ring_commit(ring);


Above is original code, rptr is updated when called, and below is your patch, my question is why do you need to get rptr twice?

@@ -1084,6 +1084,8 @@ int amdgpu_vce_ring_test_ring(struct amdgpu_ring *ring)
        if (r)
                return r;

+       rptr = amdgpu_ring_get_rptr(ring);
+
        amdgpu_ring_write(ring, VCE_CMD_END);
        amdgpu_ring_commit(ring);



On 5/27/19 12:22 PM, Li, Ching-shih (Louis) wrote:
Hi Leo,

Yes, I confirm it is the root cause for the Chrome S3 issue. Whenever system is resumed, the original instruction always gets zero. However, I have no idea why it fails, and didn’t verify this problem on CRB or any other Linux platform yet.
Although I think the ideal solution is an indicator, e.g. a register, for driver to check if related firmware and hardware are ready to work. So driver can make sure it is ok to read rptr. Without any reference document, I can only try to solve the problem by modifying driver. Debug traces reveal that only first rptr read fails, but the read in check loop is ok. Therefore, a solution comes to mind: to update rptr later for initial rptr value. Tests prove it working in Chrome platforms. Fyi~

BR,
Louis

From: Liu, Leo <Leo.Liu@amd.com><mailto:Leo.Liu@amd.com>
Sent: Monday, May 27, 2019 9:01 PM
To: S, Shirish <Shirish.S@amd.com><mailto:Shirish.S@amd.com>; Grodzovsky, Andrey <Andrey.Grodzovsky@amd.com><mailto:Andrey.Grodzovsky@amd.com>; Zhang, Jerry <Jerry.Zhang@amd.com><mailto:Jerry.Zhang@amd.com>; Deng, Emily <Emily.Deng@amd.com><mailto:Emily.Deng@amd.com>; Deucher, Alexander <Alexander.Deucher@amd.com><mailto:Alexander.Deucher@amd.com>
Cc: amd-gfx@lists.freedesktop.org<mailto:amd-gfx@lists.freedesktop.org>; Li, Ching-shih (Louis) <Ching-shih.Li@amd.com><mailto:Ching-shih.Li@amd.com>
Subject: Re: [PATCH] drm/amdgpu: fix ring test failure issue during s3 in vce 3.0



On 5/27/19 3:42 AM, S, Shirish wrote:

From: Louis Li <Ching-shih.Li@amd.com><mailto:Ching-shih.Li@amd.com>



[What]

vce ring test fails consistently during resume in s3 cycle, due to

mismatch read & write pointers.

On debug/analysis its found that rptr to be compared is not being

correctly updated/read, which leads to this failure.

Below is the failure signature:

  [drm:amdgpu_vce_ring_test_ring] *ERROR* amdgpu: ring 12 test failed

  [drm:amdgpu_device_ip_resume_phase2] *ERROR* resume of IP block <vce_v3_0> failed -110

  [drm:amdgpu_device_resume] *ERROR* amdgpu_device_ip_resume failed (-110).



[How]

fetch rptr appropriately, meaning move its read location further down

in the code flow.

With this patch applied the s3 failure is no more seen for >5k s3 cycles,

which otherwise is pretty consistent.



Signed-off-by: Louis Li <Ching-shih.Li@amd.com><mailto:Ching-shih.Li@amd.com>

---

 drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c | 2 ++

 1 file changed, 2 insertions(+)



diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c

index c021b11..92f9d46 100644

--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c

+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vce.c

@@ -1084,6 +1084,8 @@ int amdgpu_vce_ring_test_ring(struct amdgpu_ring *ring)

  if (r)

         return r;



+ rptr = amdgpu_ring_get_rptr(ring);

+

The rptr update is there:

        uint32_t rptr = amdgpu_ring_get_rptr(ring);



Are you sure this is the root cause?



Regards,

Leo







  amdgpu_ring_write(ring, VCE_CMD_END);

  amdgpu_ring_commit(ring);



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