Re: Driver directory selection for Power Supply Status chip

Re: Driver directory selection for Power Supply Status chip

[Jonathan Cameron]

On 18/04/16 20:43, Thor Thayer wrote:
> 
> 
> On 04/18/2016 11:41 AM, Lars-Peter Clausen wrote:
>> On 04/18/2016 06:14 PM, Thor Thayer wrote:
>>> Hi,
>>>
>>> The Arria10 System Resource chip (A10SR) is a SPI based MFD implementing a
>>> GPIO expander, reset controller, and power supply monitoring. I'm not sure
>>> where the driver for the A10SR power monitoring driver should reside and I'm
>>> hoping someone can offer some advice.
>>>
>>> I'd originally submitted the RFC to the HWMON list but the maintainer
>>> pointed out that it wasn't a good fit because the A10SR only indicates
>>> boolean power supply status - not the voltage level as required by HWMON.
>>>
>>> I read that IIO acts as a bridge between IO and HWMON but I'm also not sure
>>> this fits those drivers (although I did find some power supply supervistors
>>> there). It isn't quite a power supply supervisor - the A10SR is a comparator
>>> instead of an Analog-to-Digital Converter.
>>>
>>> One additional thing, the A10SR also had a number of enable bits for
>>> enabling devices external to Altera's SoC (but still on the development
>>> board). These don't quite fit into the reset controller framework but would
>>> seem to fit a MISC directory driver better.
>>>
>>> If neither IIO or MISC is a good fit, can someone suggest a more appropriate
>>> place?
>>
>> How does the device work, does it generate an interrupt when the voltage
>> level goes below the threshold? I'd like to pass the ball back and say that
>> this sounds like something that should go into hwmon.
>>
> 
> Good question but no, there is no interrupt.
> 
> The chip is actually a power supply sequencer for bringing up the
> power supplies in the correct order. Since the sequence, timings, and
> thresholds are hard coded in the chip and can't be changed
> programatically, I assume it was decided that a power fail interrupt
> was not needed. However, the status of the power (OK/Fail) can be
> read from the chip.
> 
> I was directed to look at Documentation/hwmon/sysfs-interface which
> states the units are in millivolts and I didn't see any references to
> a boolean output so I'm leaning away from hwmon.
That's one impressively uninformative output...  Hmm.
Not obvious where to put it - it doesn't fit in IIO really either.

Could report as a power supply?  There is 'health' support in there.
See Documentation/power/power_supply_class.txt
and include/linux/power_supply.h
though I'm not sure which type a fail on this would count as...
perhaps UNSPEC_FAILURE.

It's intended for batteries really - not sure how far you can stretch
that.

Cc'd linux-pm and maintainers.  Perhaps they will have a better idea!
> 
> Thank you for your reply!
> -- 
> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
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Re: Driver directory selection for Power Supply Status chip

[Guenter Roeck]

On Mon, Apr 18, 2016 at 09:06:02PM +0100, Jonathan Cameron wrote:
> On 18/04/16 20:43, Thor Thayer wrote:
> > 
> > 
> > On 04/18/2016 11:41 AM, Lars-Peter Clausen wrote:
> >> On 04/18/2016 06:14 PM, Thor Thayer wrote:
> >>> Hi,
> >>>
> >>> The Arria10 System Resource chip (A10SR) is a SPI based MFD implementing a
> >>> GPIO expander, reset controller, and power supply monitoring. I'm not sure
> >>> where the driver for the A10SR power monitoring driver should reside and I'm
> >>> hoping someone can offer some advice.
> >>>
> >>> I'd originally submitted the RFC to the HWMON list but the maintainer
> >>> pointed out that it wasn't a good fit because the A10SR only indicates
> >>> boolean power supply status - not the voltage level as required by HWMON.
> >>>
> >>> I read that IIO acts as a bridge between IO and HWMON but I'm also not sure
> >>> this fits those drivers (although I did find some power supply supervistors
> >>> there). It isn't quite a power supply supervisor - the A10SR is a comparator
> >>> instead of an Analog-to-Digital Converter.
> >>>
> >>> One additional thing, the A10SR also had a number of enable bits for
> >>> enabling devices external to Altera's SoC (but still on the development
> >>> board). These don't quite fit into the reset controller framework but would
> >>> seem to fit a MISC directory driver better.
> >>>
> >>> If neither IIO or MISC is a good fit, can someone suggest a more appropriate
> >>> place?
> >>
> >> How does the device work, does it generate an interrupt when the voltage
> >> level goes below the threshold? I'd like to pass the ball back and say that
> >> this sounds like something that should go into hwmon.
> >>
> > 
> > Good question but no, there is no interrupt.
> > 
> > The chip is actually a power supply sequencer for bringing up the
> > power supplies in the correct order. Since the sequence, timings, and
> > thresholds are hard coded in the chip and can't be changed
> > programatically, I assume it was decided that a power fail interrupt
> > was not needed. However, the status of the power (OK/Fail) can be
> > read from the chip.
> > 
> > I was directed to look at Documentation/hwmon/sysfs-interface which
> > states the units are in millivolts and I didn't see any references to
> > a boolean output so I'm leaning away from hwmon.
> That's one impressively uninformative output...  Hmm.

Please clarify what you mean with "impressively uninformative output".

FWIW, hwmon alarm attributes are boolean.

Thanks,
Guenter

> Not obvious where to put it - it doesn't fit in IIO really either.
> 
> Could report as a power supply?  There is 'health' support in there.
> See Documentation/power/power_supply_class.txt
> and include/linux/power_supply.h
> though I'm not sure which type a fail on this would count as...
> perhaps UNSPEC_FAILURE.
> 
> It's intended for batteries really - not sure how far you can stretch
> that.
> 
> Cc'd linux-pm and maintainers.  Perhaps they will have a better idea!
> > 
> > Thank you for your reply!
> > -- 
> > To unsubscribe from this list: send the line "unsubscribe linux-iio" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: Driver directory selection for Power Supply Status chip

[Thor Thayer]

Hi Guenter,

On 04/18/2016 06:50 PM, Guenter Roeck wrote:
> On Mon, Apr 18, 2016 at 09:06:02PM +0100, Jonathan Cameron wrote:
>> On 18/04/16 20:43, Thor Thayer wrote:
>>>
>>>
>>> On 04/18/2016 11:41 AM, Lars-Peter Clausen wrote:
>>>> On 04/18/2016 06:14 PM, Thor Thayer wrote:
>>>>> Hi,
>>>>>
>>>>> The Arria10 System Resource chip (A10SR) is a SPI based MFD implementing a
>>>>> GPIO expander, reset controller, and power supply monitoring. I'm not sure
>>>>> where the driver for the A10SR power monitoring driver should reside and I'm
>>>>> hoping someone can offer some advice.
>>>>>
>>>>> I'd originally submitted the RFC to the HWMON list but the maintainer
>>>>> pointed out that it wasn't a good fit because the A10SR only indicates
>>>>> boolean power supply status - not the voltage level as required by HWMON.
>>>>>
>>>>> I read that IIO acts as a bridge between IO and HWMON but I'm also not sure
>>>>> this fits those drivers (although I did find some power supply supervistors
>>>>> there). It isn't quite a power supply supervisor - the A10SR is a comparator
>>>>> instead of an Analog-to-Digital Converter.
>>>>>
>>>>> One additional thing, the A10SR also had a number of enable bits for
>>>>> enabling devices external to Altera's SoC (but still on the development
>>>>> board). These don't quite fit into the reset controller framework but would
>>>>> seem to fit a MISC directory driver better.
>>>>>
>>>>> If neither IIO or MISC is a good fit, can someone suggest a more appropriate
>>>>> place?
>>>>
>>>> How does the device work, does it generate an interrupt when the voltage
>>>> level goes below the threshold? I'd like to pass the ball back and say that
>>>> this sounds like something that should go into hwmon.
>>>>
>>>
>>> Good question but no, there is no interrupt.
>>>
>>> The chip is actually a power supply sequencer for bringing up the
>>> power supplies in the correct order. Since the sequence, timings, and
>>> thresholds are hard coded in the chip and can't be changed
>>> programatically, I assume it was decided that a power fail interrupt
>>> was not needed. However, the status of the power (OK/Fail) can be
>>> read from the chip.
>>>
>>> I was directed to look at Documentation/hwmon/sysfs-interface which
>>> states the units are in millivolts and I didn't see any references to
>>> a boolean output so I'm leaning away from hwmon.
>> That's one impressively uninformative output...  Hmm.
>
> Please clarify what you mean with "impressively uninformative output".
>
> FWIW, hwmon alarm attributes are boolean.
>
> Thanks,
> Guenter
>

Thank you for pointing out the alarms - I missed that but they would 
fit. I'll investigate further.

Thanks!

>> Not obvious where to put it - it doesn't fit in IIO really either.
>>
>> Could report as a power supply?  There is 'health' support in there.
>> See Documentation/power/power_supply_class.txt
>> and include/linux/power_supply.h
>> though I'm not sure which type a fail on this would count as...
>> perhaps UNSPEC_FAILURE.
>>
>> It's intended for batteries really - not sure how far you can stretch
>> that.
>>
>> Cc'd linux-pm and maintainers.  Perhaps they will have a better idea!
>>>
>>> Thank you for your reply!
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
>>> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>

Re: Driver directory selection for Power Supply Status chip

[Jonathan Cameron]

On 19 April 2016 00:50:15 BST, Guenter Roeck <linux@roeck-us.net> wrote:
>On Mon, Apr 18, 2016 at 09:06:02PM +0100, Jonathan Cameron wrote:
>> On 18/04/16 20:43, Thor Thayer wrote:
>> > 
>> > 
>> > On 04/18/2016 11:41 AM, Lars-Peter Clausen wrote:
>> >> On 04/18/2016 06:14 PM, Thor Thayer wrote:
>> >>> Hi,
>> >>>
>> >>> The Arria10 System Resource chip (A10SR) is a SPI based MFD
>implementing a
>> >>> GPIO expander, reset controller, and power supply monitoring. I'm
>not sure
>> >>> where the driver for the A10SR power monitoring driver should
>reside and I'm
>> >>> hoping someone can offer some advice.
>> >>>
>> >>> I'd originally submitted the RFC to the HWMON list but the
>maintainer
>> >>> pointed out that it wasn't a good fit because the A10SR only
>indicates
>> >>> boolean power supply status - not the voltage level as required
>by HWMON.
>> >>>
>> >>> I read that IIO acts as a bridge between IO and HWMON but I'm
>also not sure
>> >>> this fits those drivers (although I did find some power supply
>supervistors
>> >>> there). It isn't quite a power supply supervisor - the A10SR is a
>comparator
>> >>> instead of an Analog-to-Digital Converter.
>> >>>
>> >>> One additional thing, the A10SR also had a number of enable bits
>for
>> >>> enabling devices external to Altera's SoC (but still on the
>development
>> >>> board). These don't quite fit into the reset controller framework
>but would
>> >>> seem to fit a MISC directory driver better.
>> >>>
>> >>> If neither IIO or MISC is a good fit, can someone suggest a more
>appropriate
>> >>> place?
>> >>
>> >> How does the device work, does it generate an interrupt when the
>voltage
>> >> level goes below the threshold? I'd like to pass the ball back and
>say that
>> >> this sounds like something that should go into hwmon.
>> >>
>> > 
>> > Good question but no, there is no interrupt.
>> > 
>> > The chip is actually a power supply sequencer for bringing up the
>> > power supplies in the correct order. Since the sequence, timings,
>and
>> > thresholds are hard coded in the chip and can't be changed
>> > programatically, I assume it was decided that a power fail
>interrupt
>> > was not needed. However, the status of the power (OK/Fail) can be
>> > read from the chip.
>> > 
>> > I was directed to look at Documentation/hwmon/sysfs-interface which
>> > states the units are in millivolts and I didn't see any references
>to
>> > a boolean output so I'm leaning away from hwmon.
>> That's one impressively uninformative output...  Hmm.

It's not an alarm on anything in particular but rather simply means 'something is wrong somewhere in the power supply startup'.

>
>Please clarify what you mean with "impressively uninformative output".
>
>FWIW, hwmon alarm attributes are boolean.
>
>Thanks,
>Guenter
>
>> Not obvious where to put it - it doesn't fit in IIO really either.
>> 
>> Could report as a power supply?  There is 'health' support in there.
>> See Documentation/power/power_supply_class.txt
>> and include/linux/power_supply.h
>> though I'm not sure which type a fail on this would count as...
>> perhaps UNSPEC_FAILURE.
>> 
>> It's intended for batteries really - not sure how far you can stretch
>> that.
>> 
>> Cc'd linux-pm and maintainers.  Perhaps they will have a better idea!
>> > 
>> > Thank you for your reply!
>> > -- 
>> > To unsubscribe from this list: send the line "unsubscribe
>linux-iio" in
>> > the body of a message to majordomo@vger.kernel.org
>> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> 
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>To unsubscribe from this list: send the line "unsubscribe linux-iio" in
>the body of a message to majordomo@vger.kernel.org
>More majordomo info at  http://vger.kernel.org/majordomo-info.html

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