linux-kernel - Re: [v4,4/6] pmbus: max31785: Add fan control

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Date:   Fri, 10 Nov 2017 13:40:16 +1030
From:   Andrew Jeffery <andrew@...id.au>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     linux-hwmon@...r.kernel.org, robh+dt@...nel.org,
        mark.rutland@....com, jdelvare@...e.com, corbet@....net,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, joel@....id.au, openbmc@...ts.ozlabs.org
Subject: Re: [v4,4/6] pmbus: max31785: Add fan control

On Sun, 2017-11-05 at 07:04 -0800, Guenter Roeck wrote:
> On Fri, Nov 03, 2017 at 03:53:04PM +1100, Andrew Jeffery wrote:
> > The implementation makes use of the new fan control virtual registers
> > exposed by the pmbus core. It mixes use of the default implementations
> > with some overrides via the read/write handlers to handle FAN_COMMAND_1
> > on the MAX31785, whose definition breaks the value range into various
> > control bands dependent on RPM or PWM mode.
> > 
> > Signed-off-by: Andrew Jeffery <andrew@...id.au>
> > ---
> >  Documentation/hwmon/max31785   |   4 ++
> >  drivers/hwmon/pmbus/max31785.c | 104 ++++++++++++++++++++++++++++++++++++++++-
> >  2 files changed, 107 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/hwmon/max31785 b/Documentation/hwmon/max31785
> > index 45fb6093dec2..e9edbf11948f 100644
> > --- a/Documentation/hwmon/max31785
> > +++ b/Documentation/hwmon/max31785
> > @@ -32,6 +32,7 @@ Sysfs attributes
> >  fan[1-4]_alarm		Fan alarm.
> >  fan[1-4]_fault		Fan fault.
> >  fan[1-4]_input		Fan RPM.
> > +fan[1-4]_target		Fan input target
> >  
> >  in[1-6]_crit		Critical maximum output voltage
> >  in[1-6]_crit_alarm	Output voltage critical high alarm
> > @@ -44,6 +45,9 @@ in[1-6]_max_alarm	Output voltage high alarm
> >  in[1-6]_min		Minimum output voltage
> >  in[1-6]_min_alarm	Output voltage low alarm
> >  
> > +pwm[1-4]		Fan target duty cycle (0..255)
> > +pwm[1-4]_enable		0: full-speed, 1: manual control, 2: automatic
> > +
> >  temp[1-11]_crit		Critical high temperature
> >  temp[1-11]_crit_alarm	Chip temperature critical high alarm
> >  temp[1-11]_input	Measured temperature
> > diff --git a/drivers/hwmon/pmbus/max31785.c b/drivers/hwmon/pmbus/max31785.c
> > index 9313849d5160..0d97ddf67079 100644
> > --- a/drivers/hwmon/pmbus/max31785.c
> > +++ b/drivers/hwmon/pmbus/max31785.c
> > @@ -20,8 +20,102 @@ enum max31785_regs {
> >  
> >  #define MAX31785_NR_PAGES		23
> >  
> > +static int max31785_get_pwm(struct i2c_client *client, int page)
> > +{
> > +	int config;
> > +	int command;
> > +
> > +	config = pmbus_read_byte_data(client, page, PMBUS_FAN_CONFIG_12);
> > +	if (config < 0)
> > +		return config;
> > +
> > +	command = pmbus_read_word_data(client, page, PMBUS_FAN_COMMAND_1);
> > +	if (command < 0)
> > +		return command;
> > +
> > +	if (!(config & PB_FAN_1_RPM)) {
> > +		if (command >= 0x8000)
> > +			return 0;
> > +		else if (command >= 0x2711)
> > +			return 0x2710;
> > +
> > +		return command;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int max31785_get_pwm_mode(struct i2c_client *client, int page)
> > +{
> > +	int config;
> > +	int command;
> > +
> > +	config = pmbus_read_byte_data(client, page, PMBUS_FAN_CONFIG_12);
> > +	if (config < 0)
> > +		return config;
> > +
> > +	command = pmbus_read_word_data(client, page, PMBUS_FAN_COMMAND_1);
> > +	if (command < 0)
> > +		return command;
> > +
> > +	if (!(config & PB_FAN_1_RPM)) {
> > +		if (command >= 0x8000)
> > +			return 2;
> > +		else if (command >= 0x2711)
> > +			return 0;
> > +
> > +		return 1;
> > +	}
> > +
> > +	return (command >= 0x8000) ? 2 : 1;
> > +}
> > +
> > +static int max31785_read_word_data(struct i2c_client *client, int page,
> > +				   int reg)
> > +{
> > +	int rv;
> > +
> > +	switch (reg) {
> > +	case PMBUS_VIRT_PWM_1:
> > +		rv = max31785_get_pwm(client, page);
> > +		if (rv < 0)
> > +			return rv;
> > +
> > +		rv *= 255;
> > +		rv /= 100;
> > +		break;
> > +	case PMBUS_VIRT_PWM_ENABLE_1:
> > +		rv = max31785_get_pwm_mode(client, page);
> > +		break;
> 
> I do wonder ... does it even make sense to specify generic code
> for the new virtual attributes in the pmbus core code, or would
> it be better to have it all in this driver, at least for now ?

I think I'll pull the generic implementations out in light of my
response on 3/6. At best the generic implementation for the PWM virtual
regs is a guess. We can always put it back if others come to need it.

Cheers,

Andrew
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