Messages in this thread | | | Date | Wed, 13 Sep 2017 16:01:48 -0700 | From | Nicolin Chen <> | Subject | Re: [PATCH] ASoC: fsl_ssi: Override bit clock rate based on slot number |
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On Wed, Sep 13, 2017 at 10:02:20AM +0200, Arnaud Mouiche wrote:
> >Could you please give me a few set of examples of how you set > >set_sysclk(), set_tdm_slot() with the current driver? The idea > >here is to figure out a way to calculate the bclk in hw_params > >without getting set_sysclk() involved any more.
> Here is one, where a bclk = 4*16*fs is expected
> In another setup, there are 8 x 16 bits slots, whatever the number > of active channels is. > In this case bclk = 128 * fs > The number of slots is completely arbitrary. Some slots can even be > reserved for communication between codecs that don't communicate > with linux.
In summary, bclk = sample rate * slots * slot_width;
I will update my patch soon.
> >Unfortunately, it looks like a work around to me. I understand > >the idea of leaving set_sysclk() out there to override the bit > >clock is convenient, but it is not a standard ALSA design and > >may eventually introduce new problems like today. > > I agree. I'm not conservative at all concerning this question. > I don't see a way to remove set_sysclk without breaking current TDM > users anyway, at least for those who don't have their code > upstreamed.
Which TDM case would be broken by this removal? The only impact that I can see is that the ASoC core returns an ENOTSUPP for a set_sysclk() call now, which is something that a dai-link driver should have taken care of anyway.
> All information provided through snd_soc_dai_set_tdm_slot( cpu_dai, > mask, mask, slots, width ) should be enough > In this case, for TDM users > > bclk = slots * width * fs (where slots is != channels)
> will manage 99 % of the cases. > And the remaining 1% will concern people who need to hack the kernel > so widely they don't care about the set_sysclk removal.
A patch from those people will be always welcome.
> - fsl-asoc-card.c : *something will break since > snd_soc_dai_set_sysclk returned code is checked*
I've already submitted a patch to ignore all ENOTSUPP.
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