Re: [Intel-xe] [PATCH 01/10] drm/xe/oa: Introduce OA uapi

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

On Tue, 15 Aug 2023 19:21:23 -0700, Umesh Nerlige Ramappa wrote:
>
> On Tue, Aug 15, 2023 at 06:30:12PM -0700, Dixit, Ashutosh wrote:
> > On Tue, 15 Aug 2023 18:11:55 -0700, Umesh Nerlige Ramappa wrote:
> >>
> >> >> +	/**
> >> >> +	 * Multiple engines may be mapped to the same OA unit. The OA unit is
> >> >> +	 * identified by class:instance of any engine mapped to it.
> >> >> +	 *
> >> >> +	 * This parameter specifies the engine class and must be passed along
> >> >> +	 * with DRM_XE_OA_PROP_OA_ENGINE_INSTANCE.
> >> >> +	 */
> >> >> +	DRM_XE_OA_PROP_OA_ENGINE_CLASS,
> >> >> +
> >> >> +	/**
> >> >> +	 * This parameter specifies the engine instance and must be passed along
> >> >> +	 * with DRM_XE_OA_PROP_OA_ENGINE_CLASS.
> >> >> +	 */
> >> >> +	DRM_XE_OA_PROP_OA_ENGINE_INSTANCE,
> >> >
> >> > Because oa_unit_id has been introduced above in
> >> > drm_xe_engine_class_instance, should we remove these engine class/instance
> >> > properties? Since it seems OA streams can be opened directly against the oa
> >> > unit identified by oa_unit_id. And the driver can itself figure out the
> >> > engine class/instance from the oa_unit_id?
> >>
> >> Agree for the OA buffer use case.
> >>
> >> For query, we have used the class:instance to enable query support for
> >> specific engine instance. If we can work around that somehow, then we can
> >> do away with these 2 params. More like enable query for all engines that
> >> belong to the OAG unit. For render, it is straight forward since we have
> >> one render per OAG unit. For compute, multiple compute instances can map to
> >> one OAG unit and only one instance can support the query. So user may want
> >> to choose which instance that is. Although, I would just simplify it and
> >> support only instance 0 of compute. If UMD is okay with it, then we should
> >> be good.
> >
> > Can we enable the query (I guess "query" is MI_RPC) on all attached compute
> > engines and have the UMD execute the query on any of the attached engines?
> > Or is this mode of operation never been tried out before so risky?
>
> We cannot, since that is gated by a global configuration in HW that selects
> a specific instance to enable the query for compute (ccs_select to be
> specific). I think the limitation is that HW has only one OAC unit and only
> one ccs can use it.

OK. But iiuc there is also a context (or, in Xe, an exec_queue). So we
should be able to turn on the query on the context/exec_queue hw_engine, no?
Assuming more than one hw_engine in the context/exec_queue is an error?

Ashutosh

> >>
> >> Media engines do not support query, so we should be good for OAM.
> >>
> >> >
> >> > Separately, there is also the question of whether we want to share the Xe
> >> > OA IGT code with i915 as was done for this series. Since duplicating the
> >> > IGT code as well as all the perf tools seems a bit much.
> >> >
> >> > Thanks.
> >> > --
> >> > Ashutosh