On 12/02/2013 05:20 PM, Lorenzo Pieralisi wrote:
ARM based platforms implement a variety of power management schemes that
allow processors to enter at run-time low-power states, aka C-states
in ACPI jargon. The parameters defining these C-states vary on a per-platform
basis forcing the OS to hardcode the state parameters in platform
specific static tables whose size grows as the number of platforms supported
in the kernel increases and hampers device drivers standardization.
Therefore, this patch aims at standardizing C-state device tree bindings for
ARM platforms. Bindings define C-state parameters inclusive of entry methods
and state latencies, to allow operating systems to retrieve the
configuration entries from the device tree and initialize the related
power management drivers, paving the way for common code in the kernel
to deal with power states and removing the need for static data in current
and previous kernel versions.
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Hi Lorenzo,
thanks for the detailed description.
Just a couple of typos below.
[ ... ]
+- cpu-power-states node
+
+ Usage: Optional - On ARM systems, is a container of processor C-state
+ nodes. If the system does not provide CPU power
+ management capabilities or the processor just
+ supports WFI (C1 state) a cpu-power-states node is
+ not required.
+
+ Description: cpu-power-states node is a container node, where its
+ subnodes describe the CPU low-power C-states.
+
+ Node name must be "cpu-power-states".
+
+ The cpu-power-states node's parent node must be cpus node.
+
+ The cpu-power-states node's child nodes can be:
+
+ - one or more state nodes
+
+ The cpu-power-states node must contain the following properties:
+
+ - compatible
+ Value type: <stringlist>
+ Usage: Required
Invert the field above to be consistent with the definitions below.
[ ... ]
+ - power-depth
+ Usage: Required
+ Value type: <u32>
+ Definition: Integer value, starting from 2 (value 0 meaning
+ running and value 1 representing power depth of
+ wfi (C1)), that defines the level of depth of a
+ power state.
+ The system denotes power states with different
+ depths, an increasing value meaning less power
+ consumption and might involve powering down more
+ components. Devices that are affected by
^^^ extra space
[ ... ]
Thanks
-- Daniel
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