On Sun, 12 Aug 2012 17:01:08 +0100, Chris Wilson <chris at chris-wilson.co.uk> wrote: > On Sun, 12 Aug 2012 17:47:46 +0200, Daniel Vetter <daniel at ffwll.ch> wrote: > > On Sun, Aug 12, 2012 at 12:04:39PM +0100, Chris Wilson wrote: > > > In order to be able to ioremap_wc the GTT space, we need to remove the > > > conflicting pci_iomap from drm/i915, so we limit the register map in > > > drm/i915 to the suitable range for each generation. The benefit of doing > > > this is an order of magnitude reduction in time spent rewriting the GTT > > > entries when inserting and removing objects. For example, this halves the > > > CPU time spent in X when pushing pixels for chromium through a userptr > > > (chromium has a bug where it likes to recreate its ShmPixmap on every > > > draw). > > > > > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk> > > > > How well does this work with ums? > > > > I guess if it blows up, we could ioremap uncached, but when kms > > initializes drop that uc mapping and try to remap wc. But I fear that ums > > will map the entire bar and hence we can't just unconditionally map the > > gatt wc. > > It will work equisitely with ums. It will fail to do as it wishes and > fallback to VESA and everybody will be much happier... So having rediscovered the hard truth that i915.modeset=1 and xf86-video-2.6.0 results in nasty hangs, setting the GTT table to WC has no effect upon the ancient UMS module - it shows the retro background and appears to function. We struck lucky. \o/ -Chris -- Chris Wilson, Intel Open Source Technology Centre
