[alsa-devel] [PATCH] asoc/multi-component: fsl: add support for variable SSI FIFO depth

Tabi Timur-B04825 B04825 at freescale.com
Thu Aug 5 18:21:15 CEST 2010

Mark Brown wrote:
> This doesn't seem like a hardware issue, it seems like an issue with the
> way we've deployed the device tree.

But the FIFO depth *is* a feature of the hardware.  The SSI on the 8610 has a 
depth of 8, and the SSI on the 1022 is identical in every way except that its 
FIFO depth is 15.  Since the FIFO watermark needs to be programmed based on 
the FIFO depth, the drivers need to know that information.  The only way to 
pass that info to the drivers is via the device tree.

> I'd have strongly expected that the
> device tree was able to incoporate all the properties that are standard
> to the CPU by reference somehow (with that data being distributed
> separately to the per system device tree).

Separately?  Why?  Look at the device trees we have today.  They are full of 
nodes with all sorts of device-specific properties that describe minor 
differences among the devices across various SOCs.

Timur Tabi
Linux kernel developer

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