Re: [RFC/PATCH] dt: bindings: Define bindings for device idle states

[Pavel Machek <pavel@ucw.cz>]

Hi!

> @@ -0,0 +1,102 @@
> +Device idle states
> +========================
> +
> +A device are often capable of entering a low power state(s) when it becomes
> +idle, hence the terminology of device idle states. Entering an idle state for a
> +device helps it to avoid wasting power and reduces the leakage of current.

First things first: what do these states _really_ represent? We have
GPIOs in device tree, we have clock domains. What are these?

Actually I don't think I like this. We should describe the hardware,
not particular use case.

On what hardware would you use these new bindings?

> +Required properties:
> +- compatible:		Must contain "simple-dev, idle-state".
> +- entry-latency-ns:	An u32 value in nano-seconds representing the worst case
> +			latency required for the device to enter the idle state.
> +- exit-latency-ns:	An u32 value in nano-seconds representing the worst case
> +			wakeup latency of the device, after entry-latency-ns has
> +			passed.

u32 nanoseconds have 4sec limit, right? So anything with spinning
harddrive is out?

> +== Assigning idle states to devices ==
> +
> +Required properties:
> + - dev-idle-states:	A list of phandles pointing to the supported
> +			device idle states nodes. The list must be ordered as
> +			the shallower state - the earlier in the list.

Does such ordering really neccessarily exist?

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