drm/vc4: tests: pv-muxing: Document test scenario

We've had a couple of tests that weren't really obvious, nor did they
document what they were supposed to test. Document that to make it
hopefully more obvious.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Maíra Canal <mairacanal@riseup.net>
Link: https://lore.kernel.org/r/20230728-kms-kunit-actions-rework-v3-11-952565ccccfe@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>

drm/vc4: tests: Switch to atomic state allocation helper

Now that we have a helper that takes care of an atomic state allocation
and cleanup, we can migrate to it to simplify our tests.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Maíra Canal <mairacanal@riseup.net>
Link: https://lore.kernel.org/r/20230728-kms-kunit-actions-rework-v3-10-952565ccccfe@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>

drm/vc4: tests: pv-muxing: Switch to managed locking init

The new helper to init the locking context allows to remove some
boilerplate.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Maíra Canal <mairacanal@riseup.net>
Link: https://lore.kernel.org/r/20230728-kms-kunit-actions-rework-v3-9-952565ccccfe@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>

drm/vc4: tests: mock: Use a kunit action to unregister DRM device

The *_mock_device functions allocate a DRM device that needs to be
released using drm_dev_unregister.

Now that we have a kunit release action API, we can switch to it and
don't require any kind of garbage collection from the caller.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Maíra Canal <mairacanal@riseup.net>
Link: https://lore.kernel.org/r/20230728-kms-kunit-actions-rework-v3-8-952565ccccfe@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>

drm/vc4: tests: pv-muxing: Remove call to drm_kunit_helper_free_device()

Calling drm_kunit_helper_free_device() to clean up the resources
allocated by drm_kunit_helper_alloc_device() is now optional and not
needed in most cases.

Remove it.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Maíra Canal <mairacanal@riseup.net>
Link: https://lore.kernel.org/r/20230728-kms-kunit-actions-rework-v3-7-952565ccccfe@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>

drm/vc4: tests: Add unit test suite for the PV muxing

The HVS to PixelValve muxing code is fairly error prone and has a bunch
of arbitrary constraints due to the hardware setup.

Let's create a test suite that makes sure that the possible combinations
work and the invalid ones don't.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Link: https://lore.kernel.org/r/20221123-rpi-kunit-tests-v3-19-4615a663a84a@cerno.tech
Signed-off-by: Maxime Ripard <maxime@cerno.tech>