Re: [PATCH 07/17] drm/xe/oa: OA stream initialization (OAG)

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Mon, 27 May 2024 00:04:21 -0700, Lionel Landwerlin wrote:
>

Hi Lionel,

> > +static int xe_oa_stream_init(struct xe_oa_stream *stream,
> > +			     struct xe_oa_open_param *param)
> > +{

/snip/

> > +	stream->k_exec_q = xe_exec_queue_create(stream->oa->xe, NULL,
> > +						BIT(stream->hwe->logical_instance), 1,
> > +						stream->hwe, EXEC_QUEUE_FLAG_KERNEL, 0);
>
>
> Hi Ashutosh,
>
> On i915 the changes of configuration were pipelined in the application's
> execution just like any other submission.
>
> Creating another queue completely unsynchronized from the application's
> submissions makes this non usable in my opinion.

As we discussed previously, the plan here is to provide a drm_xe_sync array,
through stream properties, which can use to synchronize OA programming with
workload submisson.

Would that not work? If not, we can do what was done in i915. But note that
i915 still has unresolved hangs, which I believe are due to the spinner
running on the application engine (iirc repeatedly opening/closing an OA
stream will hang in i915, though it could be due to other i915
complexity). That is why thought using drm_xe_sync array is both safer and
more standard way of doing what we want to achieve.

Basically the output sync object will be signalled after registers are
programmed and also any additional OA programming delay (which is
implemented in i915 using the spinner).

This would be done both for OA stream open and changing OA stream
configuration.

Thanks.
--
Ashutosh