>-----Original Message----- >From: Takashi Iwai [mailto:tiwai@xxxxxxx] >Sent: Tuesday, October 21, 2008 5:39 PM >To: Cai, Cliff >Cc: Mark Brown; Bryan Wu; alsa-devel@xxxxxxxxxxxxxxxx >Subject: Re: [PATCH 2/3] ASoC: Blackfin: add >multi-channel supporting in Blackfin ASoC driver and AD1980 >codec driver > >At Tue, 21 Oct 2008 17:35:49 +0800, >Cai, Cliff wrote: >> >> >> >> >-----Original Message----- >> >From: Mark Brown [mailto:broonie@xxxxxxxxxxxxx] >> >Sent: Tuesday, October 21, 2008 5:16 PM >> >To: Cai, Cliff >> >Cc: Bryan Wu; alsa-devel@xxxxxxxxxxxxxxxx >> >Subject: Re: [PATCH 2/3] ASoC: Blackfin: add multi-channel >supporting >> >in Blackfin ASoC driver and AD1980 codec driver >> > >> >On Tue, Oct 21, 2008 at 05:08:31PM +0800, Cai, Cliff wrote: >> > >> >> >To be honest, I'm surprised that the multi-channel support >> >can't only >> >> >incur the extra memory consumpton when playing back a >> >> >multi-channel stream - I'd have expected the hardware to work in >> >> >the same >> >way for a >> >> >normal stereo stream even if multi-channel support is built in. >> > >> >> Yes,hardware almost works in the same way as playing a stereo >> >> stream,except That it need to fill more data to DMA memory >> >> manually,since we just simulate AC97 Controller using serial port. >> > >> >My point is that the configuration of the hardware for >multi-channel >> >playback only needs to be done when actually playing back >> >multi-channel data. When playing back stereo data it should be >> >possible to configure the hardware and do the simulation in >the same >> >way as when multi-channel support is not compiled in and avoid the >> >additional costs which that incurs. >> > >> >As well as saving memory I'd expect configuring this at runtime to >> >also save some power when playing back two or four channel data. >> > >> >> Yes, it's an ideal way,but it's not safe to allocate >continuous memory >> dynamicly, Since embedded system has limited uncached DMA memory. > >But, CONFIG_SND_MULTICHAN_SUPPORT would change any buffer >allocation behavior? I don't find it... It will change the ac97 frame size defined in bf5xx-ac97.h,the frame size the basic unit of the DMA buffer >Anyway, I agree with Mark. The setup can be ideally >dynamically changed. > > >thanks, > >Takashi > _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
