Subject: Re: ARM clock API to PowerPC

From: Benjamin Herrenschmidt <[email-masked]>
Date: Thu, 13 Aug 2009 09:15:22 +1000

> The problem is that you've got a chip which has a clock tree of its own
> which could benefit from using the clock API internally (in this case
> because it helps generalisation to the case where it's on the CPU for
> the MMC block to be able to just use the clock API for its clocks).

I see.

> Ideally the MFD core for the tmio would be able to extend the clock tree
> so that the MMC driver can work without knowing what sort of device it's
> part of.  Having the platform know about the clocks in the MFD means
> teaching each platform that might use the chip about the clocking
> structure of the chip in some way.  However, there's a concern about
> making the clock API too heavyweight for the on-SoC clocks that are the
> major application.  Things like per-clock memory consumption are an
> issue on bigger chips.

Right. Well, my proposal of linkage of clock providers via the
device-tree would definitely solve that problem for us at least,
provided the various parts of the chip are represented as nodes in the
DT.

> > Having more "generic" clock providers for off-SoC clock chips is an idea
> > that went through my mind but you may be right that it's not necessarily
> > something we need to cater for initially, it can be handled by platform
> > for now easily enough.
> 
> So long as that's clear to device tree users that should be fine.

That's my thought too.

Cheers,
Ben.