Signed-off-by: Lee Jones <lee.jo...@linaro.org> --- .../devicetree/bindings/clock/clock-bindings.txt | 38 ++++++++++++++++++++++ 1 file changed, 38 insertions(+)
diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt index 06fc6d5..daf3323 100644 --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt @@ -44,6 +44,44 @@ 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. + + Expected values are hardware clock indices. If the + clock-indices property (see below) is used, then supplied + values must correspond to one of the listed identifiers. + Using the clock-indices example below, hardware clock <2> + is missing, therefore it is considered invalid to then + list clock <2> as an always-on clock. + +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. -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/