[PATCH v5 4/4] clk: dt: Introduce binding for always-on clock support

From: Lee Jones
Date: Wed Apr 01 2015 - 08:29:41 EST

Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
.../devicetree/bindings/clock/clock-bindings.txt | 31 ++++++++++++++++++++++
1 file changed, 31 insertions(+)

diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt
index 06fc6d5..94cdda2 100644
--- a/Documentation/devicetree/bindings/clock/clock-bindings.txt
+++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
@@ -44,6 +44,37 @@ For example:
clocks by index. The names should reflect the clock output signal
names for the device.

+clock-always-on: Some hardware contains bunches of clocks which must never be
+ turned off. If drivers a) fail to obtain a reference to any
+ of these or b) give up a previously obtained reference
+ during suspend, the common clk framework will attempt to
+ disable them and a platform can fail irrecoverably as a
+ result. Usually the only way to recover from these failures
+ is to reboot.
+ To avoid either of these two scenarios from catastrophically
+ disabling an otherwise perfectly healthy running system,
+ clocks can be identified as always-on using this property
+ from inside a clocksource's node.
+ This property is not to be abused. It is only to be used to
+ protect platforms from being crippled by gated clocks, not
+ as a convenience function to avoid using the framework
+ correctly inside device drivers.
+For example:
+ oscillator {
+ #clock-cells = <1>;
+ clock-output-names = "ckil", "ckih";
+ clock-always-on = <0>, <1>;
+ };
+- this node defines a device with two clock outputs, just as in the
+ example above. The only difference being that 'ckil' and 'ckih'
+ are now identified as an always-on clocks, so the framework will
+ know to never attempt to gate them.
clock-indices: If the identifying number for the clocks in the node
is not linear from zero, then this allows the mapping of
identifiers into the clock-output-names array.

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