[Intel-gfx] [PATCH 2/2] drm/i915: re-enable rc6 by default

[Daniel Vetter]

On Mon, Nov 14, 2011 at 21:39, Eugeni Dodonov <eugeni.dodonov at intel.com> wrote:
> Most of the rc6-related hangs and major issues were addressed for the past
> months.
>
> Let's re-enable it by default to provide a more wider testing, and catch
> the remaining problems.
>
> According to tests, enablement of rc6 results in up to +50% improvements
> in power usage and battery life, so it certainly would be a nice feature
> to have enabled by default.
>
> Also, most of the issues related to rc6 seem to came from VTd, so if you
> are experiencing any problems with it, try disabling VTd in bios or using
> intel_iommu=off kernel parameter to investigate whether it solves the
> issue.
>
> Acked-by: Keith Packard <keithp at keithp.com>
> CC: Daniel Vetter <daniel.vetter at ffwll.ch>
> CC: Jesse Barnes <jbarnes at virtuousgeek.org>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=38567
> Signed-off-by: Eugeni Dodonov <eugeni.dodonov at intel.com>

Iirc the same applies to rc6 as to semaphores. We have bug reports
that it causes hard-hangs in combination with DMAR. I haven't yet
gotten around to poking the relevant reporters whether ppgtt changes
anything, because internet access here at the Intel Poland site sucks.
So again I think we need to disable this on snb when DMAR is on.
-Daniel
-- 
Daniel Vetter
daniel.vetter at ffwll.ch - +41 (0) 79 365 57 48 - http://blog.ffwll.ch