On Sun, Nov 18, 2018 at 4:56 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > > On 11/17/18 7:29 AM, Rob Herring wrote: > > On Fri, Nov 09, 2018 at 11:56:06AM +1300, Chris Packham wrote: > >> With the addition of the invert-pwm property the adt7475 needs its own > >> binding documentation rather being captured under trivial-devices.txt. > >> > >> Signed-off-by: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx> > >> --- > >> Changes in v2: > >> - use pwm-polarity attiribute to indicate normal or inverted polarity. > >> > >> .../devicetree/bindings/hwmon/adt7475.txt | 24 +++++++++++++++++++ > >> .../devicetree/bindings/trivial-devices.txt | 4 ---- > >> 2 files changed, 24 insertions(+), 4 deletions(-) > >> create mode 100644 Documentation/devicetree/bindings/hwmon/adt7475.txt > >> > >> diff --git a/Documentation/devicetree/bindings/hwmon/adt7475.txt b/Documentation/devicetree/bindings/hwmon/adt7475.txt > >> new file mode 100644 > >> index 000000000000..d9212b5e9036 > >> --- /dev/null > >> +++ b/Documentation/devicetree/bindings/hwmon/adt7475.txt > >> @@ -0,0 +1,24 @@ > >> +*ADT7475 hwmon sensor. > >> + > >> +Required properties: > >> +- compatible: One of > >> + "adi,adt7473" > >> + "adi,adt7475" > >> + "adi,adt7476" > >> + "adi,adt7490" > >> + > >> +- reg: I2C address > >> + > >> +optional properties: > >> + > >> +- pwm-polarity: This configures the polarity of the PWM. 0 > >> + (PWM_POLARITY_NORMAL) uses logic high for 100% duty cycle. 1 > >> + (PWM_POLARITY_INVERSED) uses logic low for 100% duty cycle. > > > > So we're using part of the PWM binding, but none of the rest of it? What > > is the PWM connection here? > > The chip has a built-in PWM controller to control fan speeds. PWM frequency > as well as PWM polarity are configurable. I had suggested to use the terminology > from Documentation/devicetree/bindings/pwm/pwm.txt. Other than terminology there > is no connection to a standard pwm controller. Ah, a fan controller. Please make that clear. The fan related bindings need a bit of work IMO. We have the start of something somewhat common with aspeed and npcm bindings, but they could use a bit more work. We need the fan and controller bindings to be somewhat separate where a fan node for a given type of fan doesn't depend on the controller node. AIUI, all fans are not the same, so does this controller only work with 1 type of fan and not need any more board level config? Isn't fan speed not linear with PWM duty cycle and need some sort of map. > Another option/possibility would be to use a boolean, such as pwm-polarity-inverted. > We are open to suggestions. > > > It sounds like this is common for sensors, so this should be documented > > somewhere common. > > > Sure, no problem. Any suggestion where ? hwmon/fan.txt (that doesn't exist yet.) Probably all of bindings/hwmon/ should be split up by class of device. Rob
