[Intel-gfx] frame buffer compression and 915GM

[Ben Widawsky]

On Sat, May 28, 2011 at 01:50:12AM -0700, SD wrote:
> 
> 
> --- On Fri, 5/27/11, Ben Widawsky <ben at bwidawsk.net> wrote:
> 
> > From: Ben Widawsky <ben at bwidawsk.net>
> > Subject: Re: [Intel-gfx] frame buffer compression and 915GM
> > To: "SD" <sd.domrep at yahoo.com>
> > Cc: intel-gfx at lists.freedesktop.org
> > Date: Friday, May 27, 2011, 11:48 PM
> > On Fri, May 27, 2011 at 01:51:53AM
> > -0700, SD wrote:
> > > OK, thank you. I checked it, and I got unexpected
> > answer -
> > > 
> > > FBC unsupported on this chipset.
> > 
> > I'd need to know exactly which chipset you have. For
> > example. Ironlake
> > mobile, we disabled FBC because it was actually consuming
> > more power.
> > 
> > You can check your specific chipset, and look at the
> > has_fbc field here:
> > drivers/gpu/drm/i915/i915_drv.c
> > 
> > Ben
> > 
> 
> Thanks.
> I checked it out.
> You threw FBC from i915_drv since 2.6.33, because in 2.6.32 there was not any sign of pci_id detection. And since then I got awful screen picture quality, because I start to test with Fedora 12 and then jumped to Fedora 13 with 33 kernel, and since then never had normal picture - always flickers.
> 
> I know you are all very clever here and are thinking about some Watts, but I am, like a user, thinking about my eyes first and want to tell you that you did mistake.
> May be FBC uses more power (I am not sure about it, as long 3D performance on i915gm is "nothing" anyway), but it looks like FBC helps to produce nice and smooth picture on laptop LSD.

I don't think FBC should have any positive impact on the display, but I
suppose that is a subjective thing.

You should see Jesse's commit in keithp's drm-intel-next
(c1a9f047638b27e481d097910604316b8a0d132b). If you're capable of writing
code, I'd suggest you do the same thing for intel_i915gm_info where fbc
can be enabled, but is off by default. If not, hopefully I, or someone
else will get around to it eventually.

Ben