Re: [PATCH RFC 1/1] ASoC: fsl_ssi: Make fifo watermark and maxburst settings device tree options

From: Rob Herring
Date: Thu Jan 14 2016 - 22:26:35 EST

On Thu, Jan 14, 2016 at 07:31:19PM -0600, Timur Tabi wrote:
> Nicolin Chen wrote:
> >I think DT maintainers may not give a consent towards these two
> >properties as they are not to describe the hardware but to hack
> >software configurations. (And it seems you haven't CCed them.)
> I admit it's a grey area, but the hardware doesn't work if you use the wrong
> value, and it is a fixed value per device. A p1022ds would use a different
> value than in in i.MX6, and once you pick a value, it's the same no matter
> which sample rate, buffer size, etc you choose.

We've allowed similar properties for other things like SPI controllers.

It really depends on the frequency you expect to change it. The more
often it changes, the higher up the s/w stack it should be controlled
(firmware/DT, kernel, or userspace). A function of the SOC or codec
rate, then yes DT is fine. Every user needs to tune it on the same
platform, then no, don't put it in DT. My recollection from i.MX is this
would be the former case.