[Intel-gfx] gpu outputs slave and cache flushing

[Daniel Vetter]

On Tue, Jul 30, 2013 at 09:13:48AM +0100, Chris Wilson wrote:
> On Tue, Jul 30, 2013 at 03:04:22PM +1000, Dave Airlie wrote:
> > Hey,
> > 
> > so I put a patch into intel driver a while ago to avoid doing a bo
> > flush using map/unmap for output slave device if the kernel has vmap
> > flushing
> > 
> > However on reflection I realised this only works for CPU accessing
> > devices like UDL but doesn't work for GPU accessing devices like
> > nouveau/radeon,
> > 
> > Going forward I'm sure we'll eventually get GPU sync via Maarten's
> > patches but I'm thinking I should revert this change in the intel
> > driver for now,
> > so reverse optimus can work properly
> > 
> > Anyone got any ideas for a better plan going forward, maybe a stop gap
> > before Maartens patches.
> 
> I don't think it is possible to w/a this in userspace, so let's blame
> Daniel^WBen for this mess and cheer on our knight in shining armour.
> Go Maarten! But we need to be sure there is a similar synchronisation
> point for CPU access to a foriegn dma-buf.

Yeah, as long as we haven't thought all prime drivers and dma_buf how to
sync access (and flush caches if required) userspace needs to manually
flush stuff. I don't see a way around this :(

On the plus side our QA has started another try at running with nouveau
(last time around was just too much fallout from nouveau) to run our neat
seat of prime tests. So investing into a few good tests there should pay
of nicely.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch