Kevin Hilman wrote:
> On Sun, 2007-02-11 at 18:01 +0100, Dirk Behme wrote:
> 
>>Dirk Behme wrote:
>>
>>>Kevin Hilman wrote:
>>>
>>>
>>>>Here is a patch which leaves out the raw_spinlock conversions.  It goes
>>>>on the OMAP git tree on top of -rt5 (ignoring conflicts.)  I've left out
>>>>all the raw_spinlock conversions.  This has been tested on an
>>>>OMAP1623/H2 platform.
>>>
>>>Update of Kevins update. Tested on OSK.
>>>
>>>Changes:
>>>
>>>- Remove kernel/printk.c "+    zap_rt_locks();". It's already in -rt5.
>>>
>>>- Re-add HRTIMER conversion to ads7846.c
>>>
>>>With this patch I get Oops below after playing mp3 via NFS. Add 
>>>raw_spinlock_t to sound/arm/omap/omap-alsa-dma.c like in my original 
>>>patch doesn't seem to help.
>>
>>Re-adding raw_spinlock_t to omap-alsa.h helps against this Oops.
> 
> 
> My guess the oops you sent is that you saw this crash when doing a
> Ctrl-C or otherwise stopping the playback, correct?

Nearly ;)

Even without Ctrl-C this Oops happened. Simply waiting for 
mp3 to finish and coming back to prompt triggered it.

Your patch fixes this.

> This oops is triggered by the same thread trying to take the same
> spinlock (now an rt_mutex under PREEMPT_RT.)  The following patch
> fixes the nested spinlocks,  and removes the raw_spinlock.  It applies
> on top of your latest patch.

Update to patch-2.6.20-rt5-omap3 in attachment.

Changes:

- Add Kevins fix for nested omap-alsa.c spinlocks and remove 
raw_spinlock workaround.

Thanks!

> On my OSK, I do notice however that using -rt (with and without this
> fix) mp3 playback has some audible noise under PREEMPT_RT.  Do you hear
> this too?

 > Another data point...  I only hear the noise when using 
mpg123 to play
 > an .mp3 file.  If I use aplay to play a .wav file, I'm 
not hearing any
 > noise.  I can even ping flood the target and audio plays 
without
 > problems.

I use madplay

MPEG Audio Decoder 0.15.2 (beta) - Copyright (C) 2000-2004 
Robert Leslie et al.

to play mp3. I explicitly checked it again and don't think 
there is any noise. Maybe a mpg123 related issue?

Far from it, I have the feeling that mp3 playback improves 
with -rt. In the past I had some random noise with my mp3 
test song (nobody else seemed to have ;) ). With -rt I have 
the impression that it's better.

Dirk