[alsa-devel] [RFC PATCH 1/4] alsa: make hw_params negotiation infrastructure 'bclk_ratio aware'

[Mark Brown]

On Fri, Mar 08, 2019 at 02:49:48PM -0600, Pierre-Louis Bossart wrote:

> I am not sure I fully understand the ask but wanted to point out that for
> ASoC topology-based solutions the bclk rate is typically passed as a
> parameter from userspace (w/ a request_firmware and topology parsing) and

You mean for x86 systems :)  Well, big DSP really.  It's not really
topology related.

> might be forwarded over IPC to a DSP. On some Intel platforms which can't
> support 32x fs that is typically how we represent a bclk ratio multiple of
> 25. the kernel has no idea of the relationship between the representation of
> the stream in memory and the final bit clock, only the DSP which programs
> the hardware registers knows about the latter.

> It's really quite typical that the DAI is programmed for a fixed
> configuration and the DSP takes care of the conversions. The kernel only
> deals with stream triggers and power management without know all the
> internal details of the audio graph.

I think this is more the issue with not having transitioned fully to
components which we've talked about before I think - it's related but
not quite the same thing.  In the big DSP case there's really two audio
links that aren't really connected but we're currently trying to treat
them as one since the code was designed for much smaller DSPs.
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