| Message ID | 1427891304-20160-5-git-send-email-lee.jones@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Thu, 02 Apr 2015, Geert Uytterhoeven wrote: > On Wed, Apr 1, 2015 at 2:28 PM, Lee Jones <lee.jones@linaro.org> wrote: > > Signed-off-by: Lee Jones <lee.jones@linaro.org> > > --- > > .../devicetree/bindings/clock/clock-bindings.txt | 31 ++++++++++++++++++++++ > > 1 file changed, 31 insertions(+) > > > > diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt > > index 06fc6d5..94cdda2 100644 > > --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt > > +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt > > @@ -44,6 +44,37 @@ 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. > > Please document what are the expected value(s) for this property. > I assume these are clock indices into the array of hardware clocks? > > Do they take into account sparse hardware clocks, cfr. the "clock-indices" > property below (I didn't check)? They must match a valid indices. If the clock-indices property is present, the value identified as always-on must match one of the clocks listed. I'll mention that. > > +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. > > Gr{oetje,eeting}s, > > Geert >
diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt index 06fc6d5..94cdda2 100644 --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt @@ -44,6 +44,37 @@ 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. + +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.
Signed-off-by: Lee Jones <lee.jones@linaro.org> --- .../devicetree/bindings/clock/clock-bindings.txt | 31 ++++++++++++++++++++++ 1 file changed, 31 insertions(+)