[Sound-open-firmware] Timer implementation: Haswell vs Baytrail

[Pierre-Louis Bossart]

> Can someone explain what is the difference between
> hsw vs byt timer implementation?
>
> It looks like hsw uses a generic xtensa timer
> implementation based on directly reading Xtensa
> special registers while Byt uses some bits in SHIM layer.
>
> What is the advantage of byt implementation?
>
> Also, the implementation for hsw looks generic enough
> so that it can be used by other architectures that do
> not have a shim layer, right?

IIRC in Baytrail we had "external" timer registers available in the 
SHIM, which weren't affected by frequency changes. it's literally a wall 
clock. I don't think Haswell had this.

I don't think there is any hard-set rule for the timer implementations, 
you just select and add support what's best for your hardware.