Re: [PATCH v3] drm/i915/bdw: BDW Software Turbo

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Mon, 11 Aug 2014 23:33:57 +0200
Daniel Vetter <daniel@ffwll.ch> wrote:

> On Mon, Aug 11, 2014 at 11:08:38AM -0700, Daisy Sun wrote:
> > BDW supports GT C0 residency reporting in constant time unit. Driver
> > calculates GT utilization based on C0 residency and adjusts RP
> > frequency up/down accordingly. For offscreen workload specificly,
> > set frequency to RP0.
> > 
> > Offscreen task is not restricted by frame rate, it can be
> > executed as soon as possible. Transcoding and serilized workload
> > between CPU and GPU both need high GT performance, RP0 is a good
> > option in this case. RC6 will kick in to compensate power
> > consumption when GT is not active.
> > 
> > v2: Rebase on recent drm-intel-nightly
> > v3: Add flip timerout monitor, when no flip is deteced within
> > 100ms, set frequency to RP0.
> 
> Ok, let's make this really clear:
> 
> If you wire this into the flip handling in any way, I will not merge your
> patch. The timer should be fully independant and tie into the gpu
> busy/idle handling we already have.

Sounds like Daisy won't be able to spend any more time on this either.

So we're left with this patch, which does improve things for most
cases, or no patch, which leaves things universally bad.

Unless someone wants to pick up the additional work and testing of
using a timer scheme, making sure we don't have needless wakeups, and
generally improve power/perf across even more cases than this patch.

-- 
Jesse Barnes, Intel Open Source Technology Center