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

[Rob Herring]

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

Please use get_maintainers.pl in the future.

Acked-by: Rob Herring <robh at 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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