On 12/29/23 11:25, Melissa Wen wrote:

IGT `amdgpu/amd_color/crtc-lut-accuracy` fails right at the beginning of the test execution, during atomic check, because DC rejects the bandwidth state for a fb sizing 64x64. The test was previously working with the deprecated dc_commit_state(). Now using dc_validate_with_context() approach, the atomic check needs to perform a full state validation. Therefore, set fast_validation to false in the dc_validate_global_state call for atomic check.

Fixes: b8272241ff9d ("drm/amd/display: Drop dc_commit_state in favor of dc_commit_streams") Signed-off-by: Melissa Wen mwen@igalia.com

---

Hi,

It's a long story. I was inspecting this bug report:

• https://gitlab.freedesktop.org/drm/amd/-/issues/2016

and noticed the IGT test `igt@amdgpu/amd_color@crtc-lut-accuracy` mentioned there wasn't even being executed on a laptop with DCN 2.1 (HP HP ENVY x360 Convertible 13-ay1xxx/8929). The test fails right at the beginning due to an atomic check rejection, as below:

Starting subtest: crtc-lut-accuracy (amd_color:14772) igt_kms-CRITICAL: Test assertion failure function igt_display_commit_atomic, file ../lib/igt_kms.c:4530: (amd_color:14772) igt_kms-CRITICAL: Failed assertion: ret == 0 (amd_color:14772) igt_kms-CRITICAL: Last errno: 22, Invalid argument (amd_color:14772) igt_kms-CRITICAL: error: -22 != 0 Stack trace: #0 ../lib/igt_core.c:1989 __igt_fail_assert() #1 [igt_display_commit_atomic+0x44] #2 ../tests/amdgpu/amd_color.c:159 __igt_unique____real_main395() #3 ../tests/amdgpu/amd_color.c:395 main() #4 ../sysdeps/nptl/libc_start_call_main.h:74 __libc_start_call_main() #5 ../csu/libc-start.c:128 __libc_start_main@@GLIBC_2.34() #6 [_start+0x21] Subtest crtc-lut-accuracy failed.

Checking dmesg, we can see that a bandwidth validation failure causes the atomic check rejection:

[ 711.147663] amdgpu 0000:04:00.0: [drm] Mode Validation Warning: Unknown Status failed validation. [ 711.147667] [drm:amdgpu_dm_atomic_check [amdgpu]] DC global validation failure: Bandwidth validation failure (BW and Watermark) (13) [ 711.147772] [drm:amdgpu_irq_dispatch [amdgpu]] Unregistered interrupt src_id: 243 of client_id:8 [ 711.148033] [drm:amdgpu_dm_atomic_check [amdgpu]] Atomic check failed with err: -22

I also noticed that the atomic check doesn't fail if I change the fb width and height used in the test from 64 to 66, and I can get the test execution back (and with success). However, I recall that all test cases of IGT `amd_color` were working in the past, so I bisected and found the first bad commit:

b8272241ff9d drm/amd/display: Drop dc_commit_state in favor of dc_commit_streams

Bringing the `dc_commit_state` machinery back also prevents the bandwidth validation failure, but the commit above says dc_commit_streams validation is more complete than dc_commit_state, so I discarded this approach.

After some debugging and code inspection, I found out that avoiding fast validation on dc_validate_global_state during atomic check solves the issue, but I'm not sure if this change may affect performance. I compared exec time of some IGT tests and didn't see any differences, but I recognize it doesn't provide enough evidence.

What do you think about this change? Should I examine other things? Do you see any potential issue that I should investigate? Could you recommend a better approach to assess any side-effect of not enabling fast validation in the atomic check?

Please, let me know your thoughts.

We shouldn't be doing fast updates when lock_and_validation_needed is true, so this seems to be correct.

Which is to say, applied, thanks!

Cc: stable@vger.kernel.org

Happy New Year!

Melissa

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c index 2845c884398e..4f51a7ad7a3c 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -10745,7 +10745,7 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev, DRM_DEBUG_DRIVER("drm_dp_mst_atomic_check() failed\n"); goto fail; }

• status = dc_validate_global_state(dc, dm_state->context, true);
  

• status = dc_validate_global_state(dc, dm_state->context, false);
  

  if (status != DC_OK) { DRM_DEBUG_DRIVER("DC global validation failure: %s (%d)", dc_status_to_str(status), status);