Re: [PATCH 6/7] Revert "drm/amd/display: Implement zpos property"

[Leo Li]

On 2023-08-18 04:25, Melissa Wen wrote:

On 07/26, Aurabindo Pillai wrote:

This reverts commit 6c8ff1683d30024c8cff137d30b740a405cc084e.

This patch causes IGT test case 'kms_atomic@plane-immutable-zpos' to
fail on AMDGPU hardware.

Cc: Joshua Ashton <jos...@froggi.es>
Signed-off-by: Nicholas Choi <nicholas.c...@amd.com>
---
  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c | 9 ---------
  1 file changed, 9 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c 
b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
index 2198df96ed6f..8eeca160d434 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
@@ -1468,15 +1468,6 @@ int amdgpu_dm_plane_init(struct amdgpu_display_manager 
*dm,
                drm_plane_create_blend_mode_property(plane, blend_caps);
        }

- if (plane->type == DRM_PLANE_TYPE_PRIMARY) {

-               drm_plane_create_zpos_immutable_property(plane, 0);
-       } else if (plane->type == DRM_PLANE_TYPE_OVERLAY) {
-               unsigned int zpos = 1 + drm_plane_index(plane);
-               drm_plane_create_zpos_property(plane, zpos, 1, 254);
-       } else if (plane->type == DRM_PLANE_TYPE_CURSOR) {
-               drm_plane_create_zpos_immutable_property(plane, 255);
-       }

Hi Jay and Nicholas,

I'm examining this regression and, looking at the test code, I consider
this failure is caused by an incorrect assumption in the IGT test in
which any zpos values must be in the normalized range of 0 and N planes
per CRTC.

        for (int k = 0; k < n_planes; k++) {
                int zpos;
                igt_plane_t *temp;

                temp = &display->pipes[pipe->pipe].planes[k];

                if (!igt_plane_has_prop(temp, IGT_PLANE_ZPOS))
                        continue;

                zpos = igt_plane_get_prop(temp, IGT_PLANE_ZPOS);

                igt_assert_lt(zpos, n_planes);  // test case fails here

                plane_ptr[zpos] = temp;
        }


I didn't find anything in the DRM documentation that imposes this
behavior. Also, the plane composition in the test is working correctly
with this patch and without this likely-misleading assert. In addition,
enabling zpos property increases the coverage of
`kms_atomic@plane-immutable-zpos` test (previously this part of the test
was just bypassed), so it's not a regression per se. Therefore, I'm
inclined to send a fix to IGT, instead of implementing a behavior that
fit the test but may not fit well AMD display machinery.

But first I wonder if you guys find any other test or visual check that
fail with this feature?

I checked other IGT KMS plane tests and AMD MPO tests (in `amd_plane`)
and results are preserved. If there are no other issues besides IGT
plane-immutable-zpos, I'll proceed with sending the change to IGT.

Thanks,

Melissa

Hi Melissa,

Thanks for taking a look at the IGT test. Looks like the IGT failures
are the only concerns, and I agree that it doesn't make sense to require
zpos to be normalized between 0 and number of planes.

Thanks,
Leo

-
        if (plane->type == DRM_PLANE_TYPE_PRIMARY &&
            plane_cap &&
            (plane_cap->pixel_format_support.nv12 ||
--
2.41.0