[Intel-gfx] Is MI_FLUSH_ENABLE bit 12?
daniel at ffwll.ch
Tue Dec 6 13:04:07 PST 2011
On Tue, Dec 06, 2011 at 12:21:02PM -0800, Jesse Barnes wrote:
> On Tue, 06 Dec 2011 11:56:07 -0800
> Eric Anholt <eric at anholt.net> wrote:
> > > It's one of those "been there forever" bits. A comment wouldn't hurt,
> > > but we should also put in a doc change request (in fact I think I did
> > > that but it went into a black hole).
> > Well, by "been there forever", you mean "introduced in:
> > commit a69ffdbfcba8eabf2ca9d384b578e6f28b339c61
> > Author: Zhenyu Wang <zhenyuw at linux.intel.com>
> > Date: Mon Aug 30 16:12:42 2010 +0800
> > drm/i915: Enable MI_FLUSH on Sandybridge
> > MI_FLUSH is being deprecated, but still available on Sandybridge.
> > Make sure it's enabled as userspace still uses MI_FLUSH.
> > Signed-off-by: Zhenyu Wang <zhenyuw at linux.intel.com>
> > Cc: stable at kernel.org
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>"
> > It should be removed on Ironlake, and fixed to be 12 on SNB or just
> > removed.
> No, "fixed to be 12" would just encourage people to still try it and
> break their machines. We can safely remove it now that we don't use it
> anywhere. And we can fix the docs so that if people do want to mess
> with it they won't try bit 12.
If userspace ever relied on this being enabled we cannot just disable it
now - it would break the kernel<->userspace abi on snb. You have to wait
for 5-10 years, eternity or until the last userspace using this
disappeared, whichever comes first ;-)
Mail: daniel at ffwll.ch
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