[PATCH v6 4/4] clk: dt: Introduce binding for always-on clock support

Rob Herring
2015-04-07T20:32:02Z

On Tue, Apr 7, 2015 at 1:43 PM, Lee Jones <lee.jones@linaro.org> wrote:
> Signed-off-by: Lee Jones <lee.jones@linaro.org>

Please use get_maintainers.pl in the future.

Acked-by: Rob Herring <robh@kernel.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
>
>
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