[ 110.245656] hpet1: lost 7160 rtc interrupts
[ 110.868837] [drm:drm_crtc_add_crc_entry] *ERROR* Overflow of CRC buffer, userspace reads too slow.
Also seen on APL: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_4089/shard-apl3/igt@email@example.com
[ 215.962250] [drm:drm_crtc_add_crc_entry] *ERROR* Overflow of CRC buffer, userspace reads too slow.
Now also seen on SNB: https://intel-gfx-ci.01.org/tree/drm-tip/drmtip_113/fi-snb-2520m/igt@firstname.lastname@example.org
[drm:drm_crtc_add_crc_entry] *ERROR* Overflow of CRC buffer, userspace reads too slow.
The CI Bug Log issue associated to this bug has been updated.
### New filters associated
* CFL: igt@kms_chv_cursor_fail@pipe-* - dmesg-warn-*ERROR* Overflow of CRC buffer, userspace reads too slow.
kms_rotation_crc and kms_cursor_edge_walk (the new name for kms_chv_cursor_fail) use igt_pipe_crc_start/stop to turn CRC collection on and off. Between these two calls, an internal buffer of 128 entries will capture CRC's for each frame and, if the buffer fills up and overflows, the message here will be reported.
For kms_rotation_crc at least, the manual use of start/stop is unnecessary since the test is only interested in reading single CRC's at various times and doesn't care about sequences of frame-by-frame CRC's. Thus switching it over to the igt_pipe_crc_collect_crc() which will start/stop the CRC collection around the reading of a single CRC value should solve the problem since the test won't be collecting a bunch of unwanted CRC values while it's busy doing other work. I've submitted a patch for that here: https://patchwork.freedesktop.org/series/66448/
From a quick glance, kms_cursor_edge_walk looks like it probably does need a continuous sequence of CRC values; it may just be that it's doing too long a sequence of operations between start/stop. I'll look more into the details of that test later.
Ultimately this defect should have no end-user impact since end user software doesn't utilize display CRC's. The main impact here is to our CI system, which will trip over these messages.