[igt-dev] [Intel-gfx] [PATCH igt v2] igt/gen7_forcewake_mt: Make the mmio register as volatile

[Chris Wilson]

Quoting Ville Syrjälä (2018-03-02 08:27:45)
> On Fri, Mar 02, 2018 at 08:12:35AM +0000, Chris Wilson wrote:
> > Prevent the compiler from caching reads/writes to the hw register as we
> > do want to perform mmio.
> > 
> > Whilst fixing up the mmio access, also ensure that we do not leave the
> > test with any other bits still set in the forcewake register to prevent
> > affecting other tests, as spotted by Tvrtko.
> 
> I wonder why this test isn't using intel_register_access_init() & co.?
> Maybe because the library code used to take the forcewake always? But
> that could be prevented with a setenv() now.

It could just use intel_mmio_use_pci_bar() and then
intel_register_access_init() doesn't have to worry about silly tests
trying to abuse the hw.
-Chris