Message-ID: <196d7c83-c5fd-cb85-e7bb-2f1a5ba189ae@roeck-us.net>
Date:   Tue, 11 Jul 2017 06:40:04 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Andrew Jeffery <andrew@...id.au>, linux-hwmon@...r.kernel.org
Cc:     jdelvare@...e.com, linux-kernel@...r.kernel.org, joel@....id.au,
        openbmc@...ts.ozlabs.org, msbarth@...ux.vnet.ibm.com,
        mspinler@...ux.vnet.ibm.com
Subject: Re: [RFC PATCH 2/4] pmbus: Add fan configuration support

On 07/10/2017 06:56 AM, Andrew Jeffery wrote:
> Augment PMBus support to include control of fans via the
> FAN_COMMAND_[1-4] registers, both in RPM and PWM modes. The behaviour
> of FAN_CONFIG_{1_2,3_4} and FAN_COMMAND_[1-4] are tightly coupled, and
> their interactions do not fit the existing use of struct pmbus_sensor.
> The patch introduces struct pmbus_fan_ctrl to distinguish from the
> simple sensor case, along with associated sysfs show/set implementations.
> 
> Further, the interpreting the value of FAN_COMMAND_[1-4] depends on both
> the current fan mode (RPM or PWM, as configured in
> FAN_CONFIG_{1_2,3_4}), and the device-specific behaviour for the
> register. For example, the MAX31785 chip defines the following:
> 
> PWM (m = 1, b = 0, R = 2):
>           0x0000 - 0x2710: 0 - 100% fan PWM duty cycle
>           0x2711 - 0x7fff: 100% fan PWM duty cycle
>           0x8000 - 0xffff: Ignore FAN_COMMAND_[1-4], use automatic fan control
> 
> RPM (m = 1, b = 0, R = 0):
>           0x0000 - 0x7FFF: 0 - 32,767 RPM
>           0x8000 - 0xFFFF: Ignore FAN_COMMAND_[1-4], use automatic fan control
> 
> To handle the device-specific interpretation of the FAN_COMMAND_[1-4],
> add an optional callbacks to the info struct to get/set the 'mode'
> value required for the pwm[1-n]_enable sysfs attribute. A fallback
> calculation exists if the callbacks are not populated; the fallback
> ignores device-specific ranges and tries to determine a reasonable value
> from FAN_CONFIG_{1_2,3_4} and FAN_COMMAND_[1-4].
> 

This seems overly complex, but unfortunately I don't have time for a detailed
analysis right now. Couple of comments below.

Guenter

> Signed-off-by: Andrew Jeffery <andrew@...id.au>
> ---
>   drivers/hwmon/pmbus/pmbus.h      |   7 +
>   drivers/hwmon/pmbus/pmbus_core.c | 335 +++++++++++++++++++++++++++++++++++++++
>   2 files changed, 342 insertions(+)
> 
> diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
> index bfcb13bae34b..927eabc1b273 100644
> --- a/drivers/hwmon/pmbus/pmbus.h
> +++ b/drivers/hwmon/pmbus/pmbus.h
> @@ -223,6 +223,8 @@ enum pmbus_regs {
>   #define PB_FAN_1_RPM			BIT(6)
>   #define PB_FAN_1_INSTALLED		BIT(7)
>   
> +enum pmbus_fan_mode { percent = 0, rpm };
> +
>   /*
>    * STATUS_BYTE, STATUS_WORD (lower)
>    */
> @@ -380,6 +382,11 @@ struct pmbus_driver_info {
>   	int (*identify)(struct i2c_client *client,
>   			struct pmbus_driver_info *info);
>   
> +	/* Allow the driver to interpret the fan command value */
> +	int (*get_pwm_mode)(int id, u8 fan_config, u16 fan_command);
> +	int (*set_pwm_mode)(int id, long mode, u8 *fan_config,
> +			    u16 *fan_command);
> +

It is not entirely obvious to me why this would require new callback functions.
Can you overload PMBUS_FAN_CONFIG_12 / PMBUS_FAN_CONFIG_34 or, if that does not
work for some reason, introduce a virtual register, such as PMBUS_VIRT_PWM_MODE ?

>   	/* Regulator functionality, if supported by this chip driver. */
>   	int num_regulators;
>   	const struct regulator_desc *reg_desc;
> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> index ba59eaef2e07..3b0a55bbbd2c 100644
> --- a/drivers/hwmon/pmbus/pmbus_core.c
> +++ b/drivers/hwmon/pmbus/pmbus_core.c
> @@ -69,6 +69,38 @@ struct pmbus_sensor {
>   #define to_pmbus_sensor(_attr) \
>   	container_of(_attr, struct pmbus_sensor, attribute)
>   
> +#define PB_FAN_CONFIG_RPM		PB_FAN_2_RPM
> +#define PB_FAN_CONFIG_INSTALLED		PB_FAN_2_INSTALLEDBUS_VIRT_

Something seems odd here. PB_FAN_2_INSTALLEDBUS_VIRT_ ?

> +#define PB_FAN_CONFIG_MASK(i)		(0xff << (4 * !((i) & 1)))
> +#define PB_FAN_CONFIG_GET(i, n)		(((n) >> (4 * !((i) & 1))) & 0xff)
> +#define PB_FAN_CONFIG_PUT(i, n)		(((n) & 0xff) << (4 * !((i) & 1)))
> +

Aren't there standard bit manipulation macros for that ? Either case, this is just to avoid
having to use the existing defines. Ok, but then I think it would make more sense to
make it generic, ie change the core to not use PB_FAN_2_RPM / PB_FAN_1_RPM etc.
but PB_FAN_RPM(index) everywhere.

> +struct pmbus_fan_ctrl_attr {
> +	struct device_attribute attribute;
> +	char name[PMBUS_NAME_SIZE];
> +};
> +
> +struct pmbus_fan_ctrl {
> +	struct pmbus_fan_ctrl_attr fan_target;
> +	struct pmbus_fan_ctrl_attr pwm;
> +	struct pmbus_fan_ctrl_attr pwm_enable;
> +	int index;
> +	u8 page;
> +	u8 id;
> +	u8 config;
> +	u16 command;
> +};
> +#define to_pmbus_fan_ctrl_attr(_attr) \
> +	container_of(_attr, struct pmbus_fan_ctrl_attr, attribute)
> +#define fan_target_to_pmbus_fan_ctrl(_attr) \
> +	container_of(to_pmbus_fan_ctrl_attr(_attr), struct pmbus_fan_ctrl, \
> +			fan_target)
> +#define pwm_to_pmbus_fan_ctrl(_attr) \
> +	container_of(to_pmbus_fan_ctrl_attr(_attr), struct pmbus_fan_ctrl, pwm)
> +#define pwm_enable_to_pmbus_fan_ctrl(_attr) \
> +	container_of(to_pmbus_fan_ctrl_attr(_attr), struct pmbus_fan_ctrl, \
> +			pwm_enable)
> +
>   struct pmbus_boolean {
>   	char name[PMBUS_NAME_SIZE];	/* sysfs boolean name */
>   	struct sensor_device_attribute attribute;
> @@ -806,6 +838,219 @@ static ssize_t pmbus_show_label(struct device *dev,
>   	return snprintf(buf, PAGE_SIZE, "%s\n", label->label);
>   }
>   
> +static ssize_t pmbus_show_fan_command(struct device *dev,
> +				      enum pmbus_fan_mode mode,
> +				      struct pmbus_fan_ctrl *fan, char *buf)
> +{
> +	struct i2c_client *client = to_i2c_client(dev->parent);
> +	struct pmbus_data *data = i2c_get_clientdata(client);
> +	struct pmbus_sensor sensor;
> +	long val;
> +
> +	mutex_lock(&data->update_lock);
> +
> +	if ((mode == percent && (fan->config & PB_FAN_CONFIG_RPM)) ||
> +			(mode == rpm && !(fan->config & PB_FAN_CONFIG_RPM))) {
> +		mutex_unlock(&data->update_lock);
> +		return -ENOTSUPP; /* XXX: This seems dodgy, but what to do? */

Not create the attribute in question in the first place, or return 0. The above
messes up the 'sensors' command.

> +	}
> +
> +	sensor.class = PSC_FAN;
> +	if (mode == percent)
> +		sensor.data = fan->command * 255 / 100;
> +	else
> +		sensor.data = fan->command;
> +
> +	val = pmbus_reg2data(data, &sensor);
> +
> +	mutex_unlock(&data->update_lock);
> +
> +	return snprintf(buf, PAGE_SIZE, "%ld\n", val);
> +}
> +
> +static ssize_t pmbus_show_fan_target(struct device *dev,
> +				     struct device_attribute *da, char *buf)
> +{
> +	return pmbus_show_fan_command(dev, rpm,
> +				      fan_target_to_pmbus_fan_ctrl(da), buf);
> +}
> +
> +static ssize_t pmbus_show_pwm(struct device *dev,
> +			      struct device_attribute *da, char *buf)
> +{
> +	return pmbus_show_fan_command(dev, percent, pwm_to_pmbus_fan_ctrl(da),
> +				      buf);
> +}
> +
> +static ssize_t pmbus_set_fan_command(struct device *dev,
> +				     enum pmbus_fan_mode mode,
> +				     struct pmbus_fan_ctrl *fan,
> +				     const char *buf, ssize_t count)
> +{
> +	struct i2c_client *client = to_i2c_client(dev->parent);
> +	struct pmbus_data *data = i2c_get_clientdata(client);
> +	int config_addr, command_addr;
> +	struct pmbus_sensor sensor;
> +	ssize_t rv;
> +	long val;
> +
> +	if (kstrtol(buf, 10, &val) < 0)
> +		return -EINVAL;
> +
> +	mutex_lock(&data->update_lock);
> +
> +	sensor.class = PSC_FAN;
> +
> +	val = pmbus_data2reg(data, &sensor, val);
> +
> +	if (mode == percent)
> +		val = val * 100 / 255;
> +
> +	config_addr = (fan->id < 2) ? PMBUS_FAN_CONFIG_12 : PMBUS_FAN_CONFIG_34;
> +	command_addr = config_addr + 1 + (fan->id & 1);
> +
> +	if (mode == rpm)
> +		fan->config |= PB_FAN_CONFIG_RPM;
> +	else
> +		fan->config &= ~PB_FAN_CONFIG_RPM;
> +
> +	rv = pmbus_update_byte_data(client, fan->page, config_addr,
> +				    PB_FAN_CONFIG_PUT(fan->id, fan->config),
> +				    PB_FAN_CONFIG_MASK(fan->id));
> +	if (rv < 0)
> +		goto done;
> +
> +	fan->command = val;
> +	rv = pmbus_write_word_data(client, fan->page, command_addr,
> +				   fan->command);
> +
> +done:
> +	mutex_unlock(&data->update_lock);
> +
> +	if (rv < 0)
> +		return rv;
> +
> +	return count;
> +}
> +
> +static ssize_t pmbus_set_fan_target(struct device *dev,
> +				    struct device_attribute *da,
> +				    const char *buf, size_t count)
> +{
> +	return pmbus_set_fan_command(dev, rpm,
> +				     fan_target_to_pmbus_fan_ctrl(da), buf,
> +				     count);
> +}
> +
> +static ssize_t pmbus_set_pwm(struct device *dev, struct device_attribute *da,
> +			     const char *buf, size_t count)
> +{
> +	return pmbus_set_fan_command(dev, percent, pwm_to_pmbus_fan_ctrl(da),
> +				     buf, count);
> +}
> +
> +static ssize_t pmbus_show_pwm_enable(struct device *dev,
> +				     struct device_attribute *da, char *buf)
> +{
> +	struct pmbus_fan_ctrl *fan = pwm_enable_to_pmbus_fan_ctrl(da);
> +	struct i2c_client *client = to_i2c_client(dev->parent);
> +	struct pmbus_data *data = i2c_get_clientdata(client);
> +	long mode;
> +
> +	mutex_lock(&data->update_lock);
> +
> +
> +	if (data->info->get_pwm_mode) {
> +		u8 config = PB_FAN_CONFIG_PUT(fan->id, fan->config);
> +
> +		mode = data->info->get_pwm_mode(fan->id, config, fan->command);
> +	} else {
> +		struct pmbus_sensor sensor = {
> +			.class = PSC_FAN,
> +			.data = fan->command,
> +		};
> +		long command;
> +
> +		command = pmbus_reg2data(data, &sensor);
> +
> +		/* XXX: Need to do something sensible */
> +		if (fan->config & PB_FAN_CONFIG_RPM)
> +			mode = 2;
> +		else
> +			mode = (command >= 0 && command < 100);
> +	}
> +
> +	mutex_unlock(&data->update_lock);
> +
> +	return snprintf(buf, PAGE_SIZE, "%ld\n", mode);
> +}
> +
> +static ssize_t pmbus_set_pwm_enable(struct device *dev,
> +				    struct device_attribute *da,
> +				    const char *buf, size_t count)
> +{
> +	struct pmbus_fan_ctrl *fan = pwm_enable_to_pmbus_fan_ctrl(da);
> +	struct i2c_client *client = to_i2c_client(dev->parent);
> +	struct pmbus_data *data = i2c_get_clientdata(client);
> +	int config_addr, command_addr;
> +	struct pmbus_sensor sensor;
> +	ssize_t rv = count;
> +	long mode;
> +
> +	if (kstrtol(buf, 10, &mode) < 0)
> +		return -EINVAL;
> +
> +	mutex_lock(&data->update_lock);
> +
> +	sensor.class = PSC_FAN;
> +
> +	config_addr = (fan->id < 2) ? PMBUS_FAN_CONFIG_12 : PMBUS_FAN_CONFIG_34;
> +	command_addr = config_addr + 1 + (fan->id & 1);
> +
> +	if (data->info->set_pwm_mode) {
> +		u8 config = PB_FAN_CONFIG_PUT(fan->id, fan->config);
> +		u16 command = fan->command;
> +
> +		rv = data->info->set_pwm_mode(fan->id, mode, &config, &command);
> +		if (rv < 0)
> +			goto done;
> +
> +		fan->config = PB_FAN_CONFIG_GET(fan->id, config);
> +		fan->command = command;
> +	} else {
> +		fan->config &= ~PB_FAN_CONFIG_RPM;
> +		switch (mode) {
> +		case 0:
> +		case 1:
> +			/* XXX: Safe at least? */
> +			fan->command = pmbus_data2reg(data, &sensor, 100);
> +			break;
> +		case 2:
> +		default:
> +			/* XXX: Safe at least? */
> +			fan->command = 0xffff;
> +			break;
> +		}
> +	}
> +
> +	rv = pmbus_update_byte_data(client, fan->page, config_addr,
> +				    PB_FAN_CONFIG_PUT(fan->id, fan->config),
> +				    PB_FAN_CONFIG_MASK(fan->id));
> +	if (rv < 0)
> +		goto done;
> +
> +	rv = pmbus_write_word_data(client, fan->page, command_addr,
> +				   fan->command);
> +
> +done:
> +	mutex_unlock(&data->update_lock);
> +
> +	if (rv < 0)
> +		return rv;
> +
> +	return count;
> +}
> +
>   static int pmbus_add_attribute(struct pmbus_data *data, struct attribute *attr)
>   {
>   	if (data->num_attributes >= data->max_attributes - 1) {
> @@ -1094,6 +1339,51 @@ static int pmbus_add_sensor_attrs(struct i2c_client *client,
>   	return 0;
>   }
>   
> +static int pmbus_add_fan_ctrl_attr(struct pmbus_data *data,
> +				   struct pmbus_fan_ctrl_attr *fa,
> +				   const char *name_fmt,
> +				   ssize_t (*show)(struct device *dev,
> +					   struct device_attribute *attr,
> +					   char *buf),
> +				   ssize_t (*store)(struct device *dev,
> +					   struct device_attribute *attr,
> +					   const char *buf, size_t count),
> +				   int idx)
> +{
> +	struct device_attribute *da;
> +
> +	da = &fa->attribute;
> +
> +	snprintf(fa->name, sizeof(fa->name), name_fmt, idx);
> +	pmbus_dev_attr_init(da, fa->name, 0644, show, store);
> +
> +	return pmbus_add_attribute(data, &da->attr);
> +}
> +
> +static inline int pmbus_add_fan_target_attr(struct pmbus_data *data,
> +					    struct pmbus_fan_ctrl *fan)
> +{
> +	return pmbus_add_fan_ctrl_attr(data, &fan->fan_target, "fan%d_target",
> +				       pmbus_show_fan_target,
> +				       pmbus_set_fan_target, fan->index);
> +}
> +
> +static inline int pmbus_add_pwm_attr(struct pmbus_data *data,
> +				     struct pmbus_fan_ctrl *fan)
> +{
> +
> +	return pmbus_add_fan_ctrl_attr(data, &fan->pwm, "pwm%d", pmbus_show_pwm,
> +				       pmbus_set_pwm, fan->index);
> +}
> +
> +static inline int pmbus_add_pwm_enable_attr(struct pmbus_data *data,
> +					    struct pmbus_fan_ctrl *fan)
> +{
> +	return pmbus_add_fan_ctrl_attr(data, &fan->pwm_enable, "pwm%d_enable",
> +				       pmbus_show_pwm_enable,
> +				       pmbus_set_pwm_enable, fan->index);
> +}
> +
>   static const struct pmbus_limit_attr vin_limit_attrs[] = {
>   	{
>   		.reg = PMBUS_VIN_UV_WARN_LIMIT,
> @@ -1565,6 +1855,13 @@ static const int pmbus_fan_config_registers[] = {
>   	PMBUS_FAN_CONFIG_34
>   };
>   
> +static const int pmbus_fan_command_registers[] = {
> +	PMBUS_FAN_COMMAND_1,
> +	PMBUS_FAN_COMMAND_2,
> +	PMBUS_FAN_COMMAND_3,
> +	PMBUS_FAN_COMMAND_4,
> +};
> +
>   static const int pmbus_fan_status_registers[] = {
>   	PMBUS_STATUS_FAN_12,
>   	PMBUS_STATUS_FAN_12,
> @@ -1587,6 +1884,39 @@ static const u32 pmbus_fan_status_flags[] = {
>   };
>   
>   /* Fans */
> +static int pmbus_add_fan_ctrl(struct i2c_client *client,
> +		struct pmbus_data *data, int index, int page, int id,
> +		u8 config)
> +{
> +	struct pmbus_fan_ctrl *fan;
> +	int rv;
> +
> +	fan = devm_kzalloc(data->dev, sizeof(*fan), GFP_KERNEL);
> +	if (!fan)
> +		return -ENOMEM;
> +
> +	fan->index = index;
> +	fan->page = page;
> +	fan->id = id;
> +	fan->config = config;
> +
> +	rv = _pmbus_read_word_data(client, page,
> +			pmbus_fan_command_registers[id]);
> +	if (rv < 0)
> +		return rv;
> +	fan->command = rv;
> +
> +	rv = pmbus_add_fan_target_attr(data, fan);
> +	if (rv < 0)
> +		return rv;
> +
> +	rv = pmbus_add_pwm_attr(data, fan);
> +	if (rv < 0)
> +		return rv;
> +
> +	return pmbus_add_pwm_enable_attr(data, fan);
> +}
> +
>   static int pmbus_add_fan_attributes(struct i2c_client *client,
>   				    struct pmbus_data *data)
>   {
> @@ -1624,6 +1954,11 @@ static int pmbus_add_fan_attributes(struct i2c_client *client,
>   					     PSC_FAN, true, true) == NULL)
>   				return -ENOMEM;
>   
> +			ret = pmbus_add_fan_ctrl(client, data, index, page, f,
> +						 regval);
> +			if (ret < 0)
> +				return ret;
> +
>   			/*
>   			 * Each fan status register covers multiple fans,
>   			 * so we have to do some magic.
> 

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