[lkml]   [2013]   [Jul]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] drm/i915: fix long-standing SNB regression in power consumption after resume
On Sun, Jul 14, 2013 at 09:56:45PM +0400, Konstantin Khlebnikov wrote:
> Daniel Vetter wrote:
> >On Sun, Jul 14, 2013 at 6:30 PM, Konstantin Khlebnikov
> ><> wrote:
> >>This patch fixes regression in power consumtion of sandy bridge gpu, which
> >>exists since v3.6 Sometimes after resuming from s2ram gpu starts thinking that
> >>it's extremely busy. After that it never reaches rc6 state.
> >>
> >>Bug was introduce by commit b4ae3f22d238617ca11610b29fde16cf8c0bc6e0
> >>("drm/i915: load boot context at driver init time"). Without documentation
> >>it's not clear what is happening here, probably this breaks internal state of
> >>hardware ring buffers and confuses RPS engine. Fortunately keeping forcewake
> >>during whole initialization sequence in gen6_init_clock_gating() fixes this bug.
> >>
> >>References:
> >>Signed-off-by: Konstantin Khlebnikov<>
> >
> >We already hold an forcewake reference while setting up the rps stuff,
> >should we maybe hold the forcewake for the entire duration, i.e. grab
> >it here in clock_gating and release it only in gen6/vlv_enable_rps?
> >Can you please test that version, too?
> This will be racy because rps stuff is done in separate work which might be canceled
> if intel_disable_gt_powersave() happens before its completion.

Can be fixed with a flush_delayed_work. And since that has the same
requirements wrt locking to prevent deadlocks as cancel_work_sync it would
be a drop-in replacement. Can I volunteer you to look into testing that
out a bit? Otherwise I could volunteer someone from our team.

In any case I think we should apply this trick to all platforms where
we've added the MBCTL write (i.e. snb, ivb, hsw & vlv) since rps/rc6 works
_very_ similar on all of those.

Thanks, Daniel
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 -

 \ /
  Last update: 2013-07-16 09:01    [W:0.077 / U:0.524 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site