[PATCH linux dev-4.10 v3 3/5] Documentation: hwmon: Add IBM power supply documentation

[Andrew Jeffery]

On Wed, 2017-08-02 at 21:23 -0500, Eddie James wrote:
> 
> On 08/02/2017 05:11 PM, Brandon Wyman wrote:
> > On Wed, Aug 2, 2017 at 3:25 PM, Eddie James <eajames at linux.vnet.ibm.com> wrote:
> > > > > > From: "Edward A. James" <eajames at us.ibm.com>
> > > 
> > > > > > Signed-off-by: Edward A. James <eajames at us.ibm.com>
> > > ---
> > >   Documentation/hwmon/ibmps | 53 +++++++++++++++++++++++++++++++++++++++++++++++
> > >   1 file changed, 53 insertions(+)
> > >   create mode 100644 Documentation/hwmon/ibmps
> > > 
> > > diff --git a/Documentation/hwmon/ibmps b/Documentation/hwmon/ibmps
> > > new file mode 100644
> > > index 0000000..7f13fd4
> > > --- /dev/null
> > > +++ b/Documentation/hwmon/ibmps
> > > @@ -0,0 +1,53 @@
> > > +Kernel driver ibmps
> > > +====================
> > > +
> > > +Supported chips:
> > > +  * IBM Witherspoon power supply
> > > +
> > > > > > +Author: Eddie James <eajames at us.ibm.com>
> > > +
> > > +Description
> > > +-----------
> > > +
> > > +This driver supports the IBM power supply. This driver is a client to the core
> > > +PMBus driver.
> > > +
> > > +Usage Notes
> > > +-----------
> > > +
> > > +This driver should auto-detect devices. In the event that it does not, you will
> > > +have to instantiate the devices explicitly. Please see
> > > +Documentation/i2c/instantiating-devices for details.
> > > +
> > > +Sysfs entries
> > > +-------------
> > > +
> > > +The following attributes are supported:
> > > +
> > > +curr1_alarm            Output current over-current fault.
> > > +curr1_input            Measured output current in mA.
> > > +curr1_label            "iout1"
> > > +
> > > +fan1_alarm             Fan 1 warning.
> > > +fan1_fault             Fan 1 fault.
> > > +fan1_input             Fan 1 speed in RPM.
> > > +fan2_alarm             Fan 2 warning.
> > > +fan2_fault             Fan 2 fault.
> > > +fan2_input             Fan 2 speed in RPM.
> > > +
> > > +in1_alarm              Input voltage under-voltage fault.
> > 
> > Is this the normal/regular file to put this under-voltage fault in? I
> > noticed that the UCD9200 device driver appears to be the only one
> > looking for that right now, and it has it updating in1_lcrit_alarm:
> > ucd9200:in1_lcrit_alarm         Voltage critical low alarm. From
> > VIN_UV_FAULT status.
> 
> Since this is "vin" this will provide the status of VIN_UV_FAULT. 
> Similarly, VOUT_OV_FAULT will be provided by the in2_alarm ("vout"). The 
> power supply doesn't provide limit ranges for it's values, so in order 
> to get lcrit_alarm or similar I'd have to "trick" pmbus into thinking 
> limits are being provided by the PS. This seems more simple.

I'm not across the context, but tricking pmbus is straight forward:
Implement the {read,write}_{byte,word}_data callbacks, and provide an
implementation of the register whose value you want to to fake out.

However, from Documentation/hwmon/sysfs-interface:


    Each channel or limit may have an associated alarm file, containing a
    boolean value. 1 means than an alarm condition exists, 0 means no alarm.

    Usually a given chip will either use channel-related alarms, or
    limit-related alarms, not both. The driver should just reflect the hardware.

Sounds like what Eddie's describing maybe fits the channel-related
case? Again, I haven't read though the whole series so take that with a
grain of salt.

Andrew

> 
> Thanks,
> Eddie
> 
> > 
> > > +in1_input              Measured input voltage in mV.
> > > +in1_label              "vin"
> > > +in2_alarm              Output voltage over-voltage fault.
> > > +in2_input              Measured output voltage in mV.
> > > +in2_label              "vout1"
> > > +
> > > +power1_input           Measured input power in uW.
> > > +power1_label           "pin"
> > > +
> > > +temp1_alarm            PSU inlet ambient temperature over-temperature fault.
> > > +temp1_input            Measured PSU inlet ambient temp in millidegrees C.
> > > +temp2_alarm            Secondary rectifier temp over-temperature fault.
> > > +temp2_input            Measured secondary rectifier temp in millidegrees C.
> > > +temp3_alarm            ORing FET temperature over-temperature fault.
> > > +temp3_input            Measured ORing FET temperature in millidegrees C.
> > > --
> > > 1.8.3.1
> > > 
> 
> 
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