[Intel-gfx] [PATCH 9/9] drm/i915: swizzling support for snb/ivb

[Eric Anholt]

On Fri, 11 Nov 2011 18:22:25 +0100, Daniel Vetter <daniel at ffwll.ch> wrote:
> On Fri, Nov 11, 2011 at 08:50:30AM -0800, Eric Anholt wrote:
> > On Thu, 10 Nov 2011 14:18:07 +0100, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> > > We have to do this manually. Somebody had a Great Idea.
> > > 
> > > Signed-Off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> > 
> > People playing with this when not strictly required is scary to me.
> > Manually swizzling was a world of hurt.  I got to play with things like
> > "when the management engine is enabled, it carves out the top N MB of
> > one of the dimms, and the corresponding N MB of the other dimm doesn't
> > get swizzled, and you lose".
> 
> Looks like yet another patch series of mine that scares away people ...
> 
> Would this patch be less scary when we have a test that slurps in the
> entire ram to quickly diagnose such issues? We can then either revert this
> or fix up the detection to not enable swizzling in such cases.
> 
> Also the manually swizzling is a world of hurt argument is pretty void: Up
> to very recent kernels we've advertised bit9 swizzling on snb+ without any
> swizzling actually going on. So userspace clearly doesn't rely on this
> anymore (the issue was caught by running the pread tests in i-g-t).

I was assuming you were working on this because you were planning on
building something that *used* this swizzling.  We removed all the
userland because we never got it to actually work.
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