Measurements: Massive Display-related power savings

Mike (mwester) mwester at
Wed Oct 15 06:38:01 CEST 2008

Harald Welte wrote:
> Since the patches that I sent implement all this based on the framebuffer
> blanking ioctl(), I could verify that unmodified xglamo (using 'xset s 5')
> confirms the above measurements, i.e. it automatically goes down to 59mA.
> In percent, this is a 40% reduction of idle system power consumption, i.e.
> in the case where you use the device as music player without any screen
> output but CPU running.

Can we borrow any of this technique and apply it to the GTA01, or is the
GTA01 code about as good as it gets?

> The measurements should apply to both ASU and FSO, since both just used
> backlight based blanking so far.  ASU will directly benefit since it uses
> the x screen blanking.
> FSO should switch the backlight control from the sysfs method to the
> fbdev-ioctl method.  It's backwards compatible to old kernels (which will just
> backlight-blank) and future-compatible with kernels that add the jbt6k74
> notifier and glamo fb_blank() patches.

I just checked, and Qt Extended also uses the backlight-based blanking,
so that code should switch to the fbdev-ioctl method too.

Mike (mwester)

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