Re: [PATCH v3 1/6] drm/i915/gen8: Add infrastructure to initialize WA batch buffers

["Siluvery, Arun" <arun.siluvery@linux.intel.com>]

On 05/06/2015 11:56, Chris Wilson wrote:
> On Fri, Jun 05, 2015 at 11:34:01AM +0100, Arun Siluvery wrote:
>> Some of the WA are to be applied during context save but before restore and
>> some at the end of context save/restore but before executing the instructions
>> in the ring, WA batch buffers are created for this purpose and these WA cannot
>> be applied using normal means. Each context has two registers to load the
>> offsets of these batch buffers. If they are non-zero, HW understands that it
>> need to execute these batches.
>>
>> v1: In this version two separate ring_buffer objects were used to load WA
>> instructions for indirect and per context batch buffers and they were part
>> of every context.
>>
>> v2: Chris suggested to include additional page in context and use it to load
>> these WA instead of creating separate objects. This will simplify lot of things
>> as we need not explicity pin/unpin them. Thomas Daniel further pointed that GuC
>> is planning to use a similar setup to share data between GuC and driver and
>> WA batch buffers can probably share that page. However after discussions with
>> Dave who is implementing GuC changes, he suggested to use an independent page
>> for the reasons - GuC area might grow and these WA are initialized only once and
>> are not changed afterwards so we can share them share across all contexts.
>> This version uses this approach.
>> (Thanks to Chris, Dave and Thomas for their inputs)
>
> Having moved to a shared wa_ctx for all lrc, I think it makes sense to
> then do the allocation during ring_init itself, next to the scratch/hws
> status pages. The advantage is that we don't then need to add more
> special cases to the default ctx on RCS, and its permanence is far more
> prominent. It will also be more consistent with calling it ring->wa_ctx.
>
> Since you have it already plumbed into ring init/fini, why is it partly
> done during default ctx init? Maybe all that is required a little bit of
> code and changelog explanation.
> -Chris
>
ok, it is possible to do the allocation and setup in logical_ring_init() 
itself. I wanted to group it with other wa which are setup in 
init_context().

I will also change s/reg_state/cmd.

regards
Arun


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