[Intel-gfx] [PATCH] drm/i915: enable memory self refresh on 945GM

[Li Peng]

On Fri, 2009-12-04 at 13:37 -0800, Jesse Barnes wrote:
> On Fri, 4 Dec 2009 12:20:25 -0800
> Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> 
> > On Wed, 02 Dec 2009 23:11:44 +0800
> > Li Peng <peng.li at linux.intel.com> wrote:
> > > > > Thanks for pointing out, I will fix it.
> > > > 
> > > > It seems that we should also use the FIFO_MASK/FIFO_EN on 945G
> > > > platform.
> > > > 
> > > 
> > > Yeah, should add 945G.
> > 
> > Thanks for catching this.  It seems all the chipset variations have
> > slightly different register layouts for this feature.
> > 
> > > > Do you mean that the system can't be booted correctly if we enable
> > > > the SR bit in i9xx_update_wm?
> > > > 
> > > > How about setting the another self-refresh watermark?
> > > 
> > > System boot correctly, I got screen freeze immediately after booting
> > > into desktop, can't click anything, but VT switch and system network
> > > works. 
> > > 
> > > how to calculate another self-refresh watermark ? I tried some
> > > random value, doesn't help.
> > 
> > On 915 I think you'll have to set the SR watermark to a very low
> > value.  But the docs are unclear; it may re-use the existing plane A
> > watermark if INSTPM:12 is set?  In that case you'd need to set both of
> > them to a low value, preferably with a high burst value.
> > 
> > But we should definitely get the 945 fix in ASAP and cc stable, can
> > you re-post with the fixes?
> 
> I'm testing this now on my 945GME and 915GM systems, seems solid on my
> 945GME so far (building on my slow 915 system now).  Peng, can you
> confirm it works for you too?
> 

Hello, Jesse:

Sorry for the late reply, I missed this email.

I've tried your patch on 945, but my screen got frozen after booting
into desktop for a while
I suspect the frozen is due to memory self refresh isn't disabled by H/W
automatically. Disabling 
the SR bit when graphics is busy could avoid this problem.

I also tried this patch on an old eeepc 701 which has 915GM, but don't
see obvious power improvement,
idle power are almost same before and after applying the patch.