omap-mcbsp 49022000.mcbsp: TX Buffer Overflow!

[Dave Young]

Hi Peter
On 07/20/20 at 12:32pm, Peter Ujfalusi wrote:
> Hi,
> 
> On 20/07/2020 12.03, Peter Ujfalusi wrote:
> > Hi,
> > 
> > On 14/07/2020 21.03, Jarkko Nikula wrote:
> >> Hi
> >>
> >> On 7/11/20 6:33 AM, Dave Young wrote:
> >>> Hi,
> >>>
> >>> I'm trying to use g_audio on my Nokia N900 with mainline kernel. Seems
> >>> it does not work.  No sound when I play from a laptop, and also see a
> >>> lot of error like below:
> >>> [ 4729.557647] omap-mcbsp 49022000.mcbsp: TX Buffer Overflow!
> >>> ...
> >>>
> >> Head 0dc589da873b ("Merge tag 'iommu-fixes-v5.8-rc5' of
> >> git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu") records and
> >> plays fine here (arecord -f dat |aplay), although I see some of those
> >> errors but don't hear any glitches etc.
> >>
> >> Peter, does above indicate a serious issue or is it perhaps a false
> >> alarm on OMAP3 (no audible glitches)?
> > 
> > I need to dig out my n900 or beagleXM, but it is hard to believe it is
> > not a result of a glitch.
> > The DMA is triggered by McBSP and it should write exactly what McBSP
> > expects to be receiving.
> > 
> > I can not recall any changes in the past years which would have
> > introduced regressions in McBSP or the sDMA driver.
> 
> I have booted linux-next on my BeagleXM (OMAP3630, McBSP2 <-> twl4030)
> and I don't see the TX overflow print.

Just to clarify, the sound works well on n900 for normal use cases.
The TX overflow only happens when I use it as an usb audio gadget.
Because n900 is old, I tried to use it as an external audio device.

> 
> I have checked element and threshold modes and it looks fine.
> I'm not sure why we have TX Overflow printed on n900.
> 
> >> I believe you don't have some mixer knob on, N900 audio path is somewhat
> >> complex and needs bunch of mixer switches and volumes to be set. I
> >> attached my N900 mixer scripts for you to try.
> > 
> > This could be the reason for the silence, I have asoundrc files
> > somewhere to restore a 'good' mixer config.
> > 
> >> Set first everything off:
> >> ./aic34_scripts/shutdown.sh
> >>
> >> Then enable internal digital microphone and speakers:
> >> ./aic34_scripts/dmic.sh
> >> ./aic34_scripts/speakers.sh
> >>
> >> Hopefully these help you get going :-)
> >>
> > 
> > - Péter
> > 
> > Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> > Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
> > 
> 
> - Péter
> 
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
> 

Thanks
Dave