[Intel-gfx] Framebuffer compression on GM45 disabled with KMS

[Jesse Barnes]

On Sat, 1 May 2010 01:01:12 +0100
Pedro Ribeiro <pedrib at gmail.com> wrote:

> On 1 May 2010 00:06, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> > On Fri, 30 Apr 2010 13:04:23 +0100
> > Pedro Ribeiro <pedrib at gmail.com> wrote:
> >
> >> Hi all,
> >>
> >> My Xorg.log shows
> >>
> >> (**) intel(0): Kernel mode setting active, disabling FBC.
> >> (**) intel(0): Framebuffer compression disabled
> >>
> >> Is this normal? I'm trying to lower power consumption for my
> >> laptop... Enabling FBC should do it?
> >>
> >> I have
> >> fbpercrtc=0
> >> modeset=1
> >> powersave=1
> >> lvds_downclock=1
> >> enabled on the i915 module.
> >
> > It's just a stale message, I'll remove it.  FBC will be enabled by
> > your kernel if possible (you can check /sys/kernel/debug/dri/0/ for
> > status info if you have debugfs mounted).
> >
> > Jesse
> >
> 
> Thanks for the heads up, actually measuring the power consumption
> between KMS and UMS with FBC enabled it seems that KMS wins by a very
> slim margin.
> 
> Its a great job you guys are doing with this driver!
> I see it improve steadily on every kernel release. The only things I
> still miss is the render reclock support which was removed in 2.6.32.4
> - it worked wonderfully in my machine, reducing power consumption by
> 2w when idle; and multiple ring buffer support(for libva H.264) which
> seems to be coming in the Q3 this year :-)

2W!!?  If so it would be worth resurrecting for you in the form of a
boot option or something.  The main problem is that it's not very
general; may chips will lock up when we try to reclock them this way.
But enabling it by force on specific machines is probably ok.

Jesse