drm/i915: handle FIFO oversubsription correctly
authorJesse Barnes <jbarnes@virtuousgeek.org>
Thu, 16 Jul 2009 20:01:01 +0000 (13:01 -0700)
committerEric Anholt <eric@anholt.net>
Thu, 16 Jul 2009 20:02:33 +0000 (13:02 -0700)
commit390c4dd448b1a5f04ea497c20f5ff664f8eeed01
treea9a35b483382b65673843c661e058b8561e5f911
parentdff33cfcefa31c30b72c57f44586754ea9e8f3e2
drm/i915: handle FIFO oversubsription correctly

If you're pushing a plane hard (i.e. you need most or all of the FIFO
entries just to cover your frame refresh latency), the watermark level
may end up being negative.  So fix up the signed vs. unsigned math in
the calculation function to handle this correctly, giving all available
FIFO entries to such a configuration.

Reported-by: Eric Anholt <eric@anholt.net>
Tested-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
drivers/gpu/drm/i915/intel_display.c