[alsa-devel] [PATCH 2/3] ASoC: Blackfin: add multi-channel supporting in Blackfin ASoC driver and AD1980 codec driver
Cliff.Cai at analog.com
Tue Oct 21 11:35:49 CEST 2008
>From: Mark Brown [mailto:broonie at sirena.org.uk]
>Sent: Tuesday, October 21, 2008 5:16 PM
>To: Cai, Cliff
>Cc: Bryan Wu; alsa-devel at alsa-project.org
>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
>> >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
Yes, it's an ideal way,but it's not safe to allocate continuous memory
Since embedded system has limited uncached DMA memory.
More information about the Alsa-devel