-----Original Message----- From: Takashi Iwai [mailto:tiwai@suse.de] Sent: Tuesday, October 21, 2008 6:02 PM To: Cai, Cliff Cc: Mark Brown; Bryan Wu; alsa-devel@alsa-project.org Subject: Re: [alsa-devel] [PATCH 2/3] ASoC: Blackfin: add multi-channel supporting in Blackfin ASoC driver and AD1980 codec driver
At Tue, 21 Oct 2008 17:48:56 +0800, Cai, Cliff wrote:
-----Original Message----- From: Takashi Iwai [mailto:tiwai@suse.de] Sent: Tuesday, October 21, 2008 5:39 PM To: Cai, Cliff Cc: Mark Brown; Bryan Wu; alsa-devel@alsa-project.org Subject: Re: [alsa-devel] [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@sirena.org.uk] Sent: Tuesday, October 21, 2008 5:16 PM To: Cai, Cliff Cc: Bryan Wu; alsa-devel@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
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
Ah, I see. Then I find this patch OK, at least, changes for blackfin part. Basically MULTICHAN_SUPPORT will require more resources, but it still provides the same functionality as without it.
BTW, are your changes to ad1980.c applicable unconditionally? For example,
--- a/sound/soc/codecs/ad1980.c +++ b/sound/soc/codecs/ad1980.c @@ -145,7 +145,7 @@ struct snd_soc_dai ad1980_dai = { .playback = { .stream_name = "Playback", .channels_min = 2,
.channels_max = 2,
.channels_max = 6,This won't work if the machine side doesn't support the multi-channel. Right now, blackfin is the only one, but the codec driver should be generic.
This is a problem,what's your suggestion? I think if the CPU DAI only supports stereo,alsa will omit the 6 channel support for codec,am I wrong? It works for me,since I provide two choices for CPU DAI,2 or 6 channel(through CONFIG_SND_MULTICHAN_SUPPORT).
Also, the below is dangerous:
@@ -256,6 +256,9 @@ static int ad1980_soc_probe(struct
platform_device
*pdev)
- ac97_write(codec, AC97_EXTENDED_STATUS, 0x0000);/*power on LFE
+CENTER and Surround DACs*/
This will disable all other features, too.
OK, I will only enable the DACs needed.
thanks,
Takashi