radeon issues on MacBook Pro 8,2

[Seth Forshee]

On Fri, Jan 20, 2012 at 11:09:29PM +0200, Pasi Kärkkäinen wrote:
> On Thu, Jan 19, 2012 at 02:53:17PM -0600, Seth Forshee wrote:
> > On Thu, Jan 19, 2012 at 02:48:52PM -0500, Alex Deucher wrote:
> > > On Thu, Jan 19, 2012 at 12:18 PM, Seth Forshee
> > > <seth.forshee at canonical.com> wrote:
> > > > I'm seeing several issues related to the radeon driver on a MacBook Pro
> > > > 8,2 with the following graphics card:
> > > >
> > > >  ATI Technologies Inc Whistler [AMD Radeon HD 6600M Series] [1002:6741]
> > > >
> > > > All problems were observed when using kernel version 3.2.1. None are
> > > > seen when using fglrx.
> > > >
> > > >  1. Excessive power draw. When using the radeon driver ACPI reports a
> > > >    power draw of about 30W on an idle desktop. Using fglrx brings this
> > > >    number down to 15W.
> > > 
> > > The power saving features of the open source driver are not yet as
> > > good as the closed source driver.  Please see the power management
> > > section of this page (http://wiki.x.org/wiki/RadeonFeature) for more
> > > info on the options currently available.
> > 
> > The dynpm option makes a small difference, saving about 2W. I did notice
> > an ocassional flash on the screen with this option, and the same flash
> > each time I changed the power options.
> > 
> 
> Btw how do you measure the power draw? 

You can get the instantaneous rate from the data under
/proc/acpi/battery, but I use a tool called powerstat [1], written by my
colleague Colin King. The advantage of powerstat is that it samples the
ACPI data over a period of time and reports the average and standard
deviation. That way I have a better idea of how much power is really
being drawn and the quality of the value reported.

[1] http://kernel.ubuntu.com/git?p=cking/powerstat.git