[Mesa-dev] [PATCH 26/27] i965: Disable gather push constants for null constants

Abdiel Janulgue abdiel.janulgue at linux.intel.com
Fri May 8 04:58:59 PDT 2015

On 05/07/2015 05:48 PM, Pohjolainen, Topi wrote:
> On Tue, Apr 28, 2015 at 11:08:23PM +0300, Abdiel Janulgue wrote:
>> Programming null constants with gather constant tables seems to
>> be unsupported and results in a GPU lockup even with the prescribed
>> GPU workarounds in the bspec. Found out by trial and error that
>> disabling HW gather constant when the constant state for a stage
>> needs to be nullified is the only way to go around the issue.
> Just a general question. We keep resource streamer itself always enabled
> (except for blorp of course). Does it still do something meaningful without
> gather constants or should we disable them both?

The resource streamer is just an infrastructure containing the specific
optimizations hw-generated binding tables and gather constants. The
dependency below flows from left to right.

RS_on ringbuffer --> hw-binding tables --> gather constants

So switching on gather constants require HW-gen binding tables be
enabled as well. But hw-generated binding table is not required to be
switched off for gather constants to be turned off.

The only problem with disabling both is the additional required state
setup packets to tear-down and then re-enable everything again which
increases the size of the command buffers for every 3D primitive


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