linux-kernel - Re: [RFC 0/6] Non perf based Gen Graphics OA unit driver

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Message-ID: <20151016100228.GA22732@gmail.com>
Date:	Fri, 16 Oct 2015 12:02:28 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Robert Bragg <robert@...bynine.org>,
	intel-gfx@...ts.freedesktop.org,
	Daniel Vetter <daniel.vetter@...el.com>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	Sourab Gupta <sourab.gupta@...el.com>,
	Zhenyu Wang <zhenyuw@...ux.intel.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	Kan Liang <kan.liang@...el.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Zheng Yan <zheng.z.yan@...el.com>,
	Mark Rutland <mark.rutland@....com>,
	Matt Fleming <matt.fleming@...el.com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [RFC 0/6] Non perf based Gen Graphics OA unit driver


* Peter Zijlstra <peterz@...radead.org> wrote:

> > - We may be making some technical compromises a.t.m for the sake of
> >   using perf.
> > 
> >     perf_event_open() requires events to either relate to a pid or a
> >     specific cpu core, while our device pmu relates to neither.  Events
> >     opened with a pid will be automatically enabled/disabled according
> >     to the scheduling of that process - so not appropriate for us.
> 
> Right; the traditional cpu/pid mapping doesn't work well for devices;
> but maybe, with some work, we can create something like that
> global/local render context from it; although I've no clue what form
> that would need at this time.

Could someone please help with some very basic questions, such as what the 
hardware model of the 'OA' unit model is? How are OA registers set up, how are 
their values made accessible to the host side, etc.

I see some references to 'OA' registers in:

  https://01.org/sites/default/files/documentation/intel-gfx-prm-osrc-bdw-vol03-gpu_overview_1.pdf

and I tried to find a more high level description in:

   https://01.org/linuxgraphics/documentation/hardware-specification-prms/2014-2015-intel-processors-based-broadwell-platform

but couldn't find it. (Maybe it's my fault!)

Thanks,

	Ingo
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