Messages in this thread | | | From | Fabio Estevam <> | Date | Mon, 26 Sep 2016 14:26:28 -0300 | Subject | Re: Removal of regulator-boot-on/always-on when a consumer exists |
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On Mon, Sep 26, 2016 at 1:57 PM, Mark Brown <broonie@kernel.org> wrote:
> Like I say I can't give you a definitive answer on this without looking > at the actual hardware and what it needs. Based on what you're saying > it sounds like it won't be an issue from the point of view of disrupting > other users but without knowing the hardware I can't tell if the > connected device can safely have power removed, sometimes devices don't > like having only one of many supplies removed.
Ok, let me give you more details: we power the board with an external 5V power supply, then a discrete regulator generates 3.3V to the CAN transceiver chip.
Software has no influence on this 3.3V rail, which stays powered as long as the board is powered.
According to Documentation/devicetree/bindings/regulator/regulator.txt:
- regulator-always-on: boolean, regulator should never be disabled - regulator-boot-on: bootloader/firmware enabled regulator
and the dts looks like:
reg_3p3v: regulator-3p3v { compatible = "regulator-fixed"; regulator-name = "3P3V"; regulator-min-microvolt = <3300000>; regulator-max-microvolt = <3300000>; regulator-boot-on; regulator-always-on; }; };
&can1 { pinctrl-names = "default"; pinctrl-0 = <&pinctrl_flexcan1>; xceiver-supply = <®_3p3v>; };
The flexcan driver (which is the consumer of reg_3p3v) will call regulator_disable() when can1 is not used. Calling regulator_disable on reg_3p3v will not physically remove power from the 3.3V, so should we use "regulator-always-on" or not in this case?
About "regulator-boot-on": since it was not the bootloader/firmware that was responsible for enabling such regulator, I think this could be removed from the dts.
Thanks for the clarification.
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