Tearing problem at bigger overlay sizes

[Xavier Bestel]

On Tue, 2009-01-13 at 18:20 +0100, Matthias Hopf wrote:
> On Jan 13, 09 18:07:13 +0100, Xavier Bestel wrote:
> > On Tue, 2009-01-13 at 17:41 +0100, Matthias Hopf wrote:
> > > > tear free. Sometimes the diagonal tear can be seen in one or more (2..4  
> > > > segments out of 11) of the 100 line segments. This last point is really 
> > > > puzzling, this could indicate the graphics engine is just keeping up 
> > > > with the refresh, slightly slower or slightly faster.
> > > 
> > > Could be a caching issue, pushing out the cache after each block might
> > > help.
> > 
> > Why not just after the last block ?
> 
> Because the chip might reorder memory writes, and decide for later
> blocks to be pushed out first (or even pushed out to memory w/o changing
> the cache). That way you *could* see multiple tearings.

I thought a cache flush acted like a barrier, i.e. even if reordered
between them all writes before the flush should go.

> Again, this is a lot of hand waving. Still, it might be an idea.

As you say, it's only handwaving ...

	Xav