-----Original Message----- From: Lars-Peter Clausen [mailto:lars@metafoo.de] Sent: Thursday, August 25, 2011 1:06 AM To: Liam Girdwood Cc: Dong Aisheng-B29396; alsa-devel@alsa-project.org; broonie@opensource.wolfsonmicro.com; s.hauer@pengutronix.de; linux-arm- kernel@lists.infradead.org; w.sang@pengutronix.de Subject: Re: [alsa-devel] [PATCH v2 1/1] ASoC: soc-core: check rate for symmetry only when pcm is active
On 08/24/2011 06:03 PM, Liam Girdwood wrote:
On 24/08/11 12:02, Dong Aisheng wrote:
For the playback and record using different dai links, checking !rtd->rate for symmetry may not be accurate because that pcm may be acutually not running and the default new open rate is 0, then the warning message "Not enforcing symmetric_rates" will happen each time with running arecord | aplay.
Now we only check rate for symmetry when the pcm is really active which seems more sensible.
Signed-off-by: Dong Aisheng b29396@freescale.com Cc: Mark Brown broonie@opensource.wolfsonmicro.com Cc: Liam Girdwood lrg@ti.com Cc: Sascha Hauer s.hauer@pengutronix.de
Acked-by: Liam Girdwood lrg@ti.com
I don't think the patch in it's current form is a good idea. All it does is silencing the warning instead of addressing the real issue. The issue at hand here is, that the same DAI is connected to two other DAIs and the thus shared between two PCMs. The shared DAI requires symmetric rates. This is something that is not covered by the current code, since it assumes that a DAI is not shared between different PCMs. So with this patch the warning will be gone, but it is still possible that the capture and playback stream of the DAI to be configured to run at different rates, which will obviously unwanted behavior.
Although I think that's another issue and it's a special using case. But I think it would be good if we can fix that issue by covering this wrong warning message issue also.
A more sensible solution would in my opinion be to save the current rate in the dai struct itself and not in the pcm struct. Upon opening a stream check for cpu and codec DAI whether they require symmetry. If they do and are active constraint the rate to DAIs rate. This also ensures that if boths DAIs are already active and are running at different rates there will be no valid rate for the new stream.
I have made another patch based on your idea and will send it out as RFC soon. Thanks a lot for your good suggestion.
Regards Dong Aisheng