[Mesa-dev] [PATCH] i965: Fix GPU hangs when a blorp batch is the first thing to execute.

[Kenneth Graunke]

On 05/02/2013 02:13 AM, Chris Wilson wrote:
> On Wed, May 01, 2013 at 04:28:08PM -0700, Eric Anholt wrote:
>> The GPU apparently goes looking for constants even though there are no
>> shader stages enabled, and gets stuck because we haven't told it there are
>> no constants to collect.  If any other user of the 3D pipeline had run
>> (even the Render accel of the X server!) since power on, then the in-GPU
>> constant buffers would have been set up with some contents we didn't use,
>> and we would succeed.
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=56416
>> NOTE: This is a candidate for the stable branches.
>
> The collorary to this is that DynamicStateUpperBound is programmed to an
> unsafe value and should be (0x7fff0000 | 1) for most of our hardware. The
> actual value to program requires information not easily reported by the
> kernel (just like the mappable aperture size).
> -Chris

Actually, the sensible value to program is the end of the batchbuffer. 
Which is readily available, but requires a relocation.  The reason we 
switched to 0xfffff001 was because programming it to the end of the 
batch buffer required relaxed relocation support in the kernel.

But I bumped the kernel requirements so we won't even run if the kernel 
doesn't support that, so we can put it back to the batch end if people 
think that's best.