[PATCH] drm/xe/oa: Enable Xe2+ PES disaggregation

[Lucas De Marchi]

On Tue, Sep 10, 2024 at 10:03:56PM GMT, Ashutosh Dixit wrote:
>On Tue, 10 Sep 2024 17:57:59 -0700, Lucas De Marchi wrote:
>>
>> On Tue, Sep 10, 2024 at 05:40:02PM GMT, Ashutosh Dixit wrote:
>> > On Tue, 10 Sep 2024 10:04:32 -0700, Lucas De Marchi wrote:
>> >>
>> >
>> > Hi Lucas,
>> >
>> > We had a whole email thread to figure this out :/
>> >
>> >> On Mon, Sep 09, 2024 at 09:59:33AM GMT, Ashutosh Dixit wrote:
>> >> > Xe2+ PES disaggregation for OAG needs to be enabled to obtain disaggregated
>> >> > metrics when disaggregated data is needed. There is no uapi impact of this
>> >>
>> >> it looks like the *control* for disaggregated data is only available on
>> >> xe2
>> >
>> > Correct, that is why the check below (also this is available only for OAG,
>> > not say for OAM):
>> >
>> >	if (GRAPHICS_VER(stream->oa->xe) >= 20 &&
>> >	    stream->hwe->oa_unit->type == DRM_XE_OA_UNIT_TYPE_OAG)
>> >
>> >> and we always use disaggregated, right?
>> >
>> > No we don't, please see below.
>> >
>> >>
>> >> > change.
>> >> >
>> >> > v2: Minor change to commit message
>> >> >
>> >> > Bspec: 61101
>> >>
>> >> "Note: After enabling desired disaggregation mode/s using this control
>> >> field, PES MODE_SELECT field is used to configure appropriate
>> >> disaggregation mode of corresponding PEC."
>> >>
>> >> Apparently MODE_SELECT == Aggregated is the hw default for xe2. Don't
>> >> we need to program anything else?
>> >
>> > So the code in this patch only enables disaggregation, this additional step
>> > (PES_MODE_SELECT) is still needed to actually use disaggregation. However
>> > this second step is done via OA configurations which come in from userspace
>> > (using add_config observation stream op). So userspace can request either
>> > aggregated or disaggregated data depending on the OA config it programs.
>> >
>> > The goal of this patch is only to enable disaggregation so userspace can
>> > use it if they want, otherwise they can't, they can only use
>> > aggregated.
>>
>> can you add a paragraph to the commit message stating something like
>> above?  Because it was not clear it was intentional to enable it in the
>> control and not in the PES_MODE_SELECT.
>
>I have changed the commit message to the following:
>
>"
>Enable Xe2+ PES disaggregation (for OAG) to retrieve disaggregated metrics
>when disaggregated data is needed. Userspace can select whether to receive
>aggregated or disaggregated metrics via the particular OA configuration it
>uses (programmed via DRM_XE_OBSERVATION_OP_ADD_CONFIG).
>"

looks good to me.

thanks
Lucas De Marchi

>
>I think this provides sufficient high level information, not bringing in
>stuff like PES_MODE_SELECT. Or should I mention PES_MODE_SELECT too?
>Thanks.
>
>
>
>>
>> thanks
>> Lucas De Marchi