On Tue, 28 Jul 2015, Maxime Ripard wrote: > On Mon, Jul 27, 2015 at 08:31:49AM +0100, Lee Jones wrote: > > On Mon, 27 Jul 2015, Maxime Ripard wrote: > > > > > Hi Lee, > > > > > > On Wed, Jul 22, 2015 at 02:04:15PM +0100, Lee Jones wrote: > > > > Signed-off-by: Lee Jones <[email protected]> > > > > --- > > > > .../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. > > > > Then how would you distinguish between the clocks if the provider > > provides more than a single clock? > > What I had in mind was that, you would have three cases: > > - critical-clocks is not there: no clocks are made critical > > - critical-clocks is there, but doesn't have any values: all the > clocks provided are marked critical > > - critical-clocks is there and it has a list of values: only the > clocks listed are marked critical. > > Does that make sense to you?
Yep, sounds good. -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
