Hi Lee, On Wed, Jul 22, 2015 at 02:04:15PM +0100, Lee Jones wrote: > Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx> > --- > .../devicetree/bindings/clock/clock-bindings.txt | 39 ++++++++++++++++++++++ > 1 file changed, 39 insertions(+) > > diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt > index 06fc6d5..4137034 100644 > --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt > +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt > @@ -44,6 +44,45 @@ For example: > clocks by index. The names should reflect the clock output signal > names for the device. > > +critical-clock: Some hardware contains bunches of clocks which, in normal > + circumstances, 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, it is possible that some > + Operating Systems might attempt to disable them to save power. > + If this happens 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 'critical' 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 a critical clock. I think we should also consider having it simply as a boolean. Using indices for clocks that don't have any (for example because it only provides a single clock) seem to not really make much sense. Also, since you can have a bunch of them, using critical-clocks seem more appropriate. Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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