[Intel-gfx] [PATCH v4 1/3] drm/i915/selftests: Add a GuC doorbells selftest

[Chris Wilson]

Quoting Michel Thierry (2017-11-15 18:30:27)
> The first test aims to check guc_init_doorbell_hw, changing the existing
> guc clients and doorbells state before calling it.
> 
> The second test tries to create as many clients as it is currently possible
> (currently limited to max number of doorbells) and exercise the doorbell
> alloc/dealloc code.
> 
> Since our usage mode require very few clients/doorbells, this code has
> been exercised very lightly and it's good to have a simple test for it.
> 
> As reference, this test already helped identify the bug fixed by
> commit 7f1ea2ac3017 ("drm/i915/guc: Fix doorbell id selection").
> 
> v2: Extend number of clients; check for client allocation failure when
> number of doorbells is exceeded; validate client properties; reuse
> guc_init_doorbell_hw (Chris).
> 
> v3: guc_init_doorbell_hw test added per Chris suggestion.
> 
> v4: Try to explain why guc_init_doorbell_hw exist and comment some
> details in the subtest.
> 
> Signed-off-by: Michel Thierry <michel.thierry at intel.com>
> Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>

Rebase, resend with r-bs and lets land this monster.
-Chris