[alsa-devel] [PATCH] ASoC: tlv320aic3x: Correct S24_3LE support

Mark Brown broonie at kernel.org
Fri Dec 13 15:18:14 CET 2013

On Fri, Dec 13, 2013 at 03:57:24PM +0200, Peter Ujfalusi wrote:
> On 12/13/2013 03:34 PM, Mark Brown wrote:

> > No, I'd expect the wire behaviour to be identical for any 24 bit samples
> > (that's certainly what most drivers are written for).  The memory layout
> > differences shouldn't be visible to CODEC drivers.

> We can not change the HW... for example:

This isn't a hardware issue, this is a software issue.

> twl4030/twl5030: 32 clock cycle/channel and 24 bits used out of that.

These shouldn't be advertising themselves as supporting 24 bit format
for ASoC then since they need 32 bit samples on the bus - this is
actually pretty standard for things that say they support 32 bits, they
usually just discard some of the lower bits but can cope with 32 bit on
the interface.

The reason everything says 24_LE right now is that we're being dumb
about how we do the constraints and CPUs do care about the memory
layout, not because the CODECs require the blank cycles.  Of course this
means that almost anything that does I2S should be able to advertise
arbatrary sample size support which is one of the resons we ought to be
doing stuff in the core to make this nicer.

> tlv320aic3106: 24 clock cycle/channel for 24 bit audio.

This is normal ASoC behaviour.

> The wire behavior is different and this need to be known by the CPU side as well.

This isn't the way to do it, though - if the TWL drivers were ever used
with other CPUs (admittedly unlikely) they'd run into trouble.
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