drm_format_helper_test fails Subtest: drm_test_fb_xrgb8888_to_xrgb2101010 on Big Endian machines (kernel 6.7.5, ppc64)

[Erhard Furtner]

Greetings!

I ran some kernel drm/ttm unit tests to check for quirks in the drm/ttm subsystem. One thing I found out that the drm_format_helper_test fails Subtest: drm_test_fb_xrgb8888_to_xrgb2101010 on my Talos II (ppc64) which I run in BigEndian mode:

[...]
         KTAP version 1
         # Subtest: drm_test_fb_xrgb8888_to_xrgb2101010
     # drm_test_fb_xrgb8888_to_xrgb2101010: EXPECTATION FAILED at drivers/gpu/drm/tests/drm_format_helper_test.c:995
     Expected buf == result->expected, but
         buf ==
         <00><00><f0><3f>
         result->expected ==
         <3f><f0><00><00>
         not ok 1 single_pixel_source_buffer
     # drm_test_fb_xrgb8888_to_xrgb2101010: EXPECTATION FAILED at drivers/gpu/drm/tests/drm_format_helper_test.c:995
     Expected buf == result->expected, but
         buf ==
         <00><00><f0><3f>
         result->expected ==
         <3f><f0><00><00>
         not ok 2 single_pixel_clip_rectangle
     # drm_test_fb_xrgb8888_to_xrgb2101010: EXPECTATION FAILED at drivers/gpu/drm/tests/drm_format_helper_test.c:995
     Expected buf == result->expected, but
         buf ==
         <ff> ff  ff <3f> 00  00  00  00 <00><00><f0><3f> 00 <fc><0f> 00 
         <ff><03><00><00><ff><03><f0><3f><00><fc><ff><3f><ff><ff><0f><00>
         result->expected ==
         <3f> ff  ff <ff> 00  00  00  00 <3f><f0><00><00> 00 <0f><fc> 00 
         <00><00><03><ff><3f><f0><03><ff><3f><ff><fc><00><00><0f><ff><ff>
         not ok 3 well_known_colors
     # drm_test_fb_xrgb8888_to_xrgb2101010: EXPECTATION FAILED at drivers/gpu/drm/tests/drm_format_helper_test.c:995
     Expected buf == result->expected, but
         buf ==
         <72><46><84><03><14><d4><44><04><0c><3c><2f><2a> 00  00  00  00 
          00  00  00  00 <cd><0d><1f><1b><72><46><84><03><14><d4><44><04>
          00  00  00  00  00  00  00  00 <0c><30><20><2a><cd><0d><1f><1b>
         <72><46><84><03> 00  00  00  00  00  00  00  00 
         result->expected ==
         <03><84><46><72><04><44><d4><14><2a><2f><3c><0c> 00  00  00  00 
          00  00  00  00 <1b><1f><0d><cd><03><84><46><72><04><44><d4><14>
          00  00  00  00  00  00  00  00 <2a><20><30><0c><1b><1f><0d><cd>
         <03><84><46><72> 00  00  00  00  00  00  00  00 
         not ok 4 destination_pitch
     # drm_test_fb_xrgb8888_to_xrgb2101010: pass:0 fail:4 skip:0 total:4
     not ok 9 drm_test_fb_xrgb8888_to_xrgb2101010
[...]

Looking at these results I suspect this to be an endian issue, probably affecting other BE arches too.

Full dmesg + kernel .config attached.

Regards,
Erhard F.
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