[Intel-gfx] [PATCH] drm/i915: Always wake the device to flush the GTT

[Daniel Vetter]

On Tue, Aug 29, 2017 at 03:59:36PM +0100, Chris Wilson wrote:
> Quoting Joonas Lahtinen (2017-08-29 15:54:06)
> > On Tue, 2017-08-29 at 11:33 +0100, Chris Wilson wrote:
> > > Since we hold the device wakeref when writing through the GTT (otherwise
> > > the writes would fail), we presumed that before the device sleeps those
> > > writes would naturally be flushed and that we wouldn't need our mmio
> > > read trick. However, that presumption seems false and a sleepy bxt seems
> > > to require us to always manually flush the GTT writes prior to direct
> > > access.
> > > 
> > > Fixes: e2a2aa36a509 ("drm/i915: Check we have an wake device before flushing GTT writes")
> > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > > Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > 
> > Got any Bugzilla, Testcase, Tested-by?
> 
> Original bugzilla hasn't been reopened, so I its looks like they were
> happy enough with the original patches that fixed the problem on my bxt.
> The testcase seems to be very system dependent, my suspicion is that it
> has to do with the wacky runtime pm exhibited by CI bxt.

CI bxt doesn't have displays, which means we shut down a lot more when
it's running. Does this indicate a huge gem test gap where we should run
plenty of gem testcases with all the outputs shut down?

Or just the need to add a pile more tests to pm_rpm?

Would be good if testcase review is a part of review, and not just "code
does what the commit message says" ... The latter should be the
trivial-most part of review really.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch