[PATCH igt v6 5/6] tests: Add kms_mmap_write_crc for cache coherency tests

[Chris Wilson]

On Wed, Dec 16, 2015 at 08:25:42PM -0200, Tiago Vignatti wrote:
> This program can be used to detect when CPU writes in the dma-buf mapped object
> don't land in scanout due cache incoherency.
> 
> Although this seems a problem inherently of non-LCC machines ("Atom"), this
> particular test catches a cache dirt on scanout on LLC machines as well. It's
> inspired in Ville's kms_pwrite_crc.c and can be used also to test the
> correctness of the driver's begin_cpu_access and end_cpu_access (which requires
> i915 implementation.
> 
> To see the need for flush, one has to run this same binary a few times cause
> it's not 100% reproducible -- what I usually do is the following, using '-n'
> option to not call the sync ioctls:
> 
>     $ while ((1)) ; do ./kms_mmap_write_crc -n; done  # in terminal A
>     $ find /                                          # in terminal B

Sounds like we need a igt_fork_memhog_helper() and repeat the test for
20s? until faiure.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre