[LAU] OpenMoko FreeRunner and Real Time Kernel

[Ken Restivo]

On Mon, Jul 14, 2008 at 02:46:57PM +0200, Anders Dahnielson wrote:
> On Mon, Jul 14, 2008 at 11:28, Ken Restivo <ken at restivo.org> wrote:
> 
> > I just received my OpenMoko FreeRunner phone and have been poking around in
> > it, trying to learn my way around it.
> >
> > I found this interesting:
> >
> >        root at om-gta02:~# cat /proc/version
> >        Linux version 2.6.24 (build at barbie) (gcc version 4.1.2) #1 PREEMPT
> > Thu Apr 24 08:23:36 CST 2008
> >
> > Hmm... the FreeRunner ships with an Ingo patched RT kernel?
> 
> 
> Nope. It would otherwise say "PREEMPT RT" like this:
> 
> Linux monolith 2.6.24.7-rt8 #2 SMP PREEMPT RT
> 


Really? I've been running a home-made Ingo patched RT kernel on my laptop for over a year now, and I get this:

	[ken at asus ~]$ cat /proc/version 
	Linux version 2.6.21-rt1-1 (root at asus) (gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-21)) #1 SMP PREEMPT Thu May 3 00:41:41 PDT 2007


No "RT" there, but I definitely know it is an RT kernel, because I patched it myself.

But, this whole thing is merely a curiosity anyway, since the FreeRunner doesn't have enough CPU to do much audio stuff. In fact PulseAudio is so slow on this phone that the audio hiccups when just playing an OGG file using ogg123, if the terminal application is open and updating with ogg123's stderr output. I'm told this is to do with the ARM's lack of support for atomic operations, which PulseAudio requires, and the use of interrupt masking and spinlocks as a hack around that.

-ken