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

[Lucas De Marchi]

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.

thanks
Lucas De Marchi