Re: Re: au8830 - front / rear channels swapped after first play and Surround40

[Raymond <rayau@netvigator.com>]

> >  No, thats not a bug. Thats normal.
>
>
> AFAIK the FIFO error occurs only one time, the first time data is
> being DMA'ed. It could be that this error is some kind of data
> underrun, and it does only happen once, because we never flush the
> FIFO's when stopping a stream. Remaining data in the FIFO's may be
> messing the channel deinterlacer, because the amount of data loaded in
> the fifo is random, generating a random offset. Since the the PCI bus
> is 32 bit wide, that problem would not affect stereo streams, because
> one 32 bit transaction maps to two 16 bit samples. Only where a frame
> is more that 32bits, this problem would become apparent. This is just
> a theory, but maybe it could be worth a try, to enforce a absolute
> flush of the FIFO data when stopping a DMA stream.

The "vortex: IRQ fifo error" message happen once when the first play is
a stereo or 4 channels sound and it do not happen when the first play is
a MONO sound on my au8830.

Using "vortex_adbdma_stopfifo()" instead of vortex_adbdma_pausefifo()"
in snd_vortex_pcm_trigger() (just like the last version of au88x0 in
alsa-driver before it merged into alsa-kernel) seem to fix the
front/rear channels swap when playing 4 channels sound in au8830.

However the message "vortex: IRQ fifo error" will appear more than once
in the kernel log, it is quite annoying when a lot of these message is
displayed on the screen (not always) during the shutdown of the linux.






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