i915 update to Linux 3.8 ready!

[Ed Maste]

On 9 March 2016 at 22:02, Ed Maste <emaste at freebsd.org> wrote:
>
> I found reports that Linux introduced a regression on Sandy Bridge
> power consumption sometime around Linux 3.6 that was fixed after 3.8.
> Those reports are specifically for an increase after a suspend-resume
> cycle; something gets confused and causes the GPU to never enter rc6.
> It's not exactly the same symptom, as I see increased consumption
> after reboot and loading i915 (before starting X), but certainly seems
> related.
>
> Anyhow, with that patch applied after a suspend-resume cycle I'm back
> to a reasonable power consumption -- around 15W in X with Firefox
> running. The patch is in https://reviews.freebsd.org/D5599.

Some further testing suggests the power consumption's back to normal
after a suspend+resume cycle, without the patch in D5599. I may have
mixed up something in my experiment yesterday or perhaps there's some
intermittent behaviour.

If anyone else has Sandy Bridge laptops (Thinkpad X220, T420 etc.) I'd
really appreciate hearing about test results.