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[RFC,1/3] dt-bindings: hwmon: Add tachometer interrupt to pwm-fan

Message ID 1548860827-29796-2-git-send-email-stefan.wahren@i2se.com
State Changes Requested, archived
Headers show
Series hwmon: pwm-fan: Add RPM support | expand

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Commit Message

Stefan Wahren Jan. 30, 2019, 3:07 p.m. UTC
This adds the tachometer interrupt to the pwm-fan binding, which is
necessary for RPM support.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
---
 Documentation/devicetree/bindings/hwmon/pwm-fan.txt | 3 +++
 1 file changed, 3 insertions(+)

Comments

Guenter Roeck Jan. 30, 2019, 5:28 p.m. UTC | #1
On Wed, Jan 30, 2019 at 04:07:05PM +0100, Stefan Wahren wrote:
> This adds the tachometer interrupt to the pwm-fan binding, which is
> necessary for RPM support.
> 
> Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
> ---
>  Documentation/devicetree/bindings/hwmon/pwm-fan.txt | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> index 49ca5d8..7f69b0b 100644
> --- a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> +++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> @@ -8,6 +8,9 @@ Required properties:
>  
>  Optional properties:
>  - fan-supply    : phandle to the regulator that provides power to the fan
> +- interrupts    : contains a single interrupt specifier which describes the
> +                  tachometer pin output of a 2 pulse-per-revolution fan.
> +                  See interrupt-controller/interrupts.txt for the format.

So a hypothetical {1,4} pulse-per-revolution fan would explicitly not be
supported ? Why ?

Guenter
Stefan Wahren Jan. 30, 2019, 8:23 p.m. UTC | #2
Hi Guenter,

> Guenter Roeck <linux@roeck-us.net> hat am 30. Januar 2019 um 18:28 geschrieben:
> 
> 
> On Wed, Jan 30, 2019 at 04:07:05PM +0100, Stefan Wahren wrote:
> > This adds the tachometer interrupt to the pwm-fan binding, which is
> > necessary for RPM support.
> > 
> > Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
> > ---
> >  Documentation/devicetree/bindings/hwmon/pwm-fan.txt | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> > index 49ca5d8..7f69b0b 100644
> > --- a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> > +++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> > @@ -8,6 +8,9 @@ Required properties:
> >  
> >  Optional properties:
> >  - fan-supply    : phandle to the regulator that provides power to the fan
> > +- interrupts    : contains a single interrupt specifier which describes the
> > +                  tachometer pin output of a 2 pulse-per-revolution fan.
> > +                  See interrupt-controller/interrupts.txt for the format.
> 
> So a hypothetical {1,4} pulse-per-revolution fan would explicitly not be
> supported ? Why ?

i could add an additional property to specify the pulse per revolution and use the 2 as default (according to the Intel spec for 4 pin pwm fan) which should fit in most cases.

> 
> Guenter
Guenter Roeck Jan. 30, 2019, 8:35 p.m. UTC | #3
On Wed, Jan 30, 2019 at 09:23:31PM +0100, Stefan Wahren wrote:
> Hi Guenter,
> 
> > Guenter Roeck <linux@roeck-us.net> hat am 30. Januar 2019 um 18:28 geschrieben:
> > 
> > 
> > On Wed, Jan 30, 2019 at 04:07:05PM +0100, Stefan Wahren wrote:
> > > This adds the tachometer interrupt to the pwm-fan binding, which is
> > > necessary for RPM support.
> > > 
> > > Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
> > > ---
> > >  Documentation/devicetree/bindings/hwmon/pwm-fan.txt | 3 +++
> > >  1 file changed, 3 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> > > index 49ca5d8..7f69b0b 100644
> > > --- a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> > > +++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> > > @@ -8,6 +8,9 @@ Required properties:
> > >  
> > >  Optional properties:
> > >  - fan-supply    : phandle to the regulator that provides power to the fan
> > > +- interrupts    : contains a single interrupt specifier which describes the
> > > +                  tachometer pin output of a 2 pulse-per-revolution fan.
> > > +                  See interrupt-controller/interrupts.txt for the format.
> > 
> > So a hypothetical {1,4} pulse-per-revolution fan would explicitly not be
> > supported ? Why ?
> 
> i could add an additional property to specify the pulse per revolution and use the 2 as default (according to the Intel spec for 4 pin pwm fan) which should fit in most cases.
> 
That would be a possibility and make sense, but that is not
the point here.  The "interrupts" property does not and should
not care how many pulses per revolution the fan provides.

Guenter
Stefan Wahren Jan. 31, 2019, 8:02 a.m. UTC | #4
Hi Guenter,

Am 30.01.19 um 21:35 schrieb Guenter Roeck:
> On Wed, Jan 30, 2019 at 09:23:31PM +0100, Stefan Wahren wrote:
>> Hi Guenter,
>>
>>> Guenter Roeck <linux@roeck-us.net> hat am 30. Januar 2019 um 18:28 geschrieben:
>>>
>>>
>>> On Wed, Jan 30, 2019 at 04:07:05PM +0100, Stefan Wahren wrote:
>>>> This adds the tachometer interrupt to the pwm-fan binding, which is
>>>> necessary for RPM support.
>>>>
>>>> Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
>>>> ---
>>>>  Documentation/devicetree/bindings/hwmon/pwm-fan.txt | 3 +++
>>>>  1 file changed, 3 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
>>>> index 49ca5d8..7f69b0b 100644
>>>> --- a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
>>>> +++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
>>>> @@ -8,6 +8,9 @@ Required properties:
>>>>  
>>>>  Optional properties:
>>>>  - fan-supply    : phandle to the regulator that provides power to the fan
>>>> +- interrupts    : contains a single interrupt specifier which describes the
>>>> +                  tachometer pin output of a 2 pulse-per-revolution fan.
>>>> +                  See interrupt-controller/interrupts.txt for the format.
>>> So a hypothetical {1,4} pulse-per-revolution fan would explicitly not be
>>> supported ? Why ?
>> i could add an additional property to specify the pulse per revolution and use the 2 as default (according to the Intel spec for 4 pin pwm fan) which should fit in most cases.
>>
> That would be a possibility and make sense, but that is not
> the point here.  The "interrupts" property does not and should
> not care how many pulses per revolution the fan provides.

sorry, i'm not sure what's the problem about. Do you want me to use a
GPIO instead of interrupt?

Or is it the wording here?

Suggestion:

contains a single interrupt specifier which is describes the tachometer
output of the fan as an input

Stefan

>
> Guenter
Guenter Roeck Jan. 31, 2019, 5:19 p.m. UTC | #5
On Thu, Jan 31, 2019 at 09:02:33AM +0100, Stefan Wahren wrote:
> Hi Guenter,
> 
> Am 30.01.19 um 21:35 schrieb Guenter Roeck:
> > On Wed, Jan 30, 2019 at 09:23:31PM +0100, Stefan Wahren wrote:
> >> Hi Guenter,
> >>
> >>> Guenter Roeck <linux@roeck-us.net> hat am 30. Januar 2019 um 18:28 geschrieben:
> >>>
> >>>
> >>> On Wed, Jan 30, 2019 at 04:07:05PM +0100, Stefan Wahren wrote:
> >>>> This adds the tachometer interrupt to the pwm-fan binding, which is
> >>>> necessary for RPM support.
> >>>>
> >>>> Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
> >>>> ---
> >>>>  Documentation/devicetree/bindings/hwmon/pwm-fan.txt | 3 +++
> >>>>  1 file changed, 3 insertions(+)
> >>>>
> >>>> diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> >>>> index 49ca5d8..7f69b0b 100644
> >>>> --- a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> >>>> +++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
> >>>> @@ -8,6 +8,9 @@ Required properties:
> >>>>  
> >>>>  Optional properties:
> >>>>  - fan-supply    : phandle to the regulator that provides power to the fan
> >>>> +- interrupts    : contains a single interrupt specifier which describes the
> >>>> +                  tachometer pin output of a 2 pulse-per-revolution fan.
> >>>> +                  See interrupt-controller/interrupts.txt for the format.
> >>> So a hypothetical {1,4} pulse-per-revolution fan would explicitly not be
> >>> supported ? Why ?
> >> i could add an additional property to specify the pulse per revolution and use the 2 as default (according to the Intel spec for 4 pin pwm fan) which should fit in most cases.
> >>
> > That would be a possibility and make sense, but that is not
> > the point here.  The "interrupts" property does not and should
> > not care how many pulses per revolution the fan provides.
> 
> sorry, i'm not sure what's the problem about. Do you want me to use a
> GPIO instead of interrupt?
> 
> Or is it the wording here?
> 

You wording limits the use of interrupts with pwm fans to fans with
2 pulses per revolution. You do not explain why that restriction would
be required or even make sense, or why it should be associated with
the 'interrupts' property.

Logically I assume that is because you expect an interrupt per pulse,
but that is not explained (or what the interrupt is expected to be
used for in the first place - it might, after all, be some kind of
error interrupt).

Guenter
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
index 49ca5d8..7f69b0b 100644
--- a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
+++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt
@@ -8,6 +8,9 @@  Required properties:
 
 Optional properties:
 - fan-supply    : phandle to the regulator that provides power to the fan
+- interrupts    : contains a single interrupt specifier which describes the
+                  tachometer pin output of a 2 pulse-per-revolution fan.
+                  See interrupt-controller/interrupts.txt for the format.
 
 Example:
 	fan0: pwm-fan {