[Intel-gfx] [PATCH] add LVDS downclocking support

[Erik Andrén]

Jesse Barnes wrote:
> On Fri, 7 Aug 2009 20:35:36 +0200
> Erik Andrén <erik.andren at gmail.com> wrote:
> 
>> 2009/8/7 Jesse Barnes <jbarnes at virtuousgeek.org>:
>>> On Mon, 23 Mar 2009 00:30:11 +0000
>>> Steven J Newbury <steve at snewbury.org.uk> wrote:
>>>
>>>> On Sun, 2009-03-22 at 20:18 +0100, Erik Andrén wrote:
>>>>> -----BEGIN PGP SIGNED MESSAGE-----
>>>>> Hash: SHA1
>>>>>
>>>>>
>>>>>
>>>>> Jesse Barnes wrote:
>>>>>> This is a refreshed patch from Matthew Garrett to enable LVDS
>>>>>> downclocking. 965+ hardware can do this automatically, but
>>>>>> other 9xx chips need some help. So this patch adds some damage
>>>>>> code to track idle time.  If we're idle for more than 500ms we
>>>>>> downclock the display based on the value calculated at mode
>>>>>> set time.
>>>>>>
>>>>>> Comments & testing appreciated.  I've only tested on my GM45 so
>>>>>> far, and I think to fully realize the benefits we'll need to
>>>>>> enable self refresh, but it should help on many platforms
>>>>>> as-is.
>>>>>>
>>>>> Hi,
>>>>> I've tested this on my 965GM laptop applied on top of Ubuntu
>>>>> Jauntys 2.6.3 version of the intel driver. When measuring with
>>>>> my Energy Monitor 3000 [1] I did not record any power savings at
>>>>> all. In fact, I saw an increase of a couple of deciwatts. (Could
>>>>> be a measuring error though).
>>>>> Otherwise the system seemed stable and functioned as expected.
>>>>>
>>>>> What is the expected power decrease when using this patch?
>>>>>
>>>>> Best regards,
>>>>> Erik Andrén
>>>>>
>>>>>
>>>>> [1]
>>>>> http://www.alamaison.com.au/p/361923/voltcraft-plus-energy-monitor-3000.html
>>>> I'm not surprised you didn't see any change measuring power usage
>>>> at the outlet.  Laptop power supplies are rarely switched mode, and
>>>> typically provide their full rating while in use.  They aren't
>>>> typically designed with energy efficiency in mind.
>>>>
>>>> If you want to measure the energy efficiency of a laptop, your best
>>>> bet is powertop when running from battery.
>>> Have you guys had a chance to test the latest patchset from Matthew
>>> and myself?  Seems to save quite a bit of power on my GM45 and
>>> 915GM test machines...
>>>
>> What are the software requirements to test these patches out?
> 
> We've been testing & developing against Eric's drm-intel-next branch as
> of a couple of weeks ago...  If you have a KMS setup working, you'd
> just need to load the i915 driver with the patch built in.
> 

Hi,
I just cloned Eric's drm-intel tree from git.kernel.org and applied
the patch. It didn't apply cleanly, some small bits were rejected.
Anyway, with the patch I experience constant flashes when in Xorg mode.

Matthew, against what tree is the patch supposed to build against?

Best regards,
Erik