[Mesa-dev] [PATCH] r600g: fix lockups with dual_src_blend v2

[Vadim Girlin]

On Tue, 2012-08-21 at 13:59 +0200, Michel Dänzer wrote:
> On Die, 2012-08-21 at 15:42 +0400, Vadim Girlin wrote: 
> > Disable blending when dual_src_blend is enabled and number of color exports
> > in the current fragment shader is less than 2.
> > 
> > Fixes lockups with ext_framebuffer_multisample-
> > alpha-to-coverage-dual-src-blend piglit test.
> > 
> > Signed-off-by: Vadim Girlin <vadimgirlin at gmail.com>
> 
> Shouldn't this rather be handled in the state tracker?

Maybe, but I'm not sure. If other hardware can live with such
configuration, then probably it doesn't make sense to implement any
special handling for that case in the state tracker. This lockup is a
hw-specific problem.

Also I think it makes sense to have some protection from lockups in the
driver even if it will be handled in the state tracker. Any future
changes or bugs in the state tracker could restore current behaviour,
and we'll have to spend some time on debugging the same lockup one more
time. Also we could hit the same problem with any other future state
trackers.

Vadim