[Mesa-dev] [RFC] i965: Fix border color on Sandybridge and Ivybridge.

[Eric Anholt]

On Fri, 20 Jan 2012 04:16:00 -0800, Kenneth Graunke <kenneth at whitecape.org> wrote:
> While reading through the simulator, I found some interesting code that
> looks like it checks the sampler default color pointer against the bound
> set in STATE_BASE_ADDRESS.  On failure, it appears to program it to a
> bogus but in-bound value.
> 
> So I decided to try programming a legitimate bound, and lo and behold,
> border color worked.  Unfortunately, it's not entirely reliable: piglit
> tests (such as tex-border-1) will still fail if you run them in a loop.
> 
> +91 piglits (or thereabouts).
> 
> This patch causes serious regressions and should not be pushed as-is.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=28924
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>

SO AWESOME.  Also, it fixes lightsmark on ivb!  I was meaning to write a
FS hack to test my theory that border color was lightsmark's problem (it
sure looked like it), and you beat me with a fix.

> -       OUT_BATCH(1); /* Dynamic state upper bound */
> +       /* Dynamic state upper bound.  Although the documentation says that
> +	* programming it to zero will cause it to be ignored, that is a lie.
> +	* If this isn't programmed to a real bound, the sampler border color
> +	* pointer is rejected, causing border color to mysteriously fail.
> +	*/
> +       OUT_BATCH(((uintptr_t) intel->batch.bo + intel->batch.bo->size) | 1);

You're stuffing some userspace pointer into this field.  It doesn't have
any relation to the GPU address.  You were looking for:

       OUT_RELOC(intel->batch.bo,
		 I915_GEM_DOMAIN_INSTRUCTION, 0,
		 intel->batch.bo->size | 1);
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