On Mon, Oct 17, 2011 at 05:02:05PM +0200, Arnd Bergmann wrote:

On Monday 17 October 2011, Sascha Hauer wrote:

quoted

The following is an attempt to represent the clocktree of a i.MX53 in
the devicetree. I created this to see how it would look like and to
start a discussion whether we want to move in this direction or not.

Very good, thanks for getting this started!

quoted

Some things to consider:

- It seems to be very flexible. A board can customize the clock tree
  by just adding some clk-parent=<phandle> properties to the muxers.
- clocks can easily be associated with devices.

but:

- The following example registers 127 new platform devices and it's
  not even complete. This adds significant overhead to initialization.

I don't understand enough about the clock trees to understand if the
dts representation is good, but it I don't see a reason to represent
it as lots of platform devices in linux. We can have lots of device_nodes
in the device tree that are not a platform_device but we can still
access them through the of_*() functions. Ideally, we would encapsulate
all the clock tree parsing in the clk subsystem and provide high-level
interfaces to clkdev drivers from there.

Still we have to parse the compatible stuff and have to match a clock
entry to the corresponding driver. If we don't use platform devices here
I think we have to be careful to not create something which resembles
the platform devices with similar overhead.

Sascha

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