Re: [PATCH v2 1/5] hwmon: (max31790) Rework to use regmap

[Václav Kubernát]

Hi Guenter,

Thank you for the comments. I will fix the issues in a V3 patch.

About the mutex: I was looking at regmap and saw it did locking by
itself. But I suppose writing still has to be locked, because the
write function writes more than once. I will add the mutex back.

Václav

út 30. 3. 2021 v 0:27 odesílatel Guenter Roeck <linux@xxxxxxxxxxxx> napsal:
>
> On Tue, Mar 16, 2021 at 06:54:58PM +0100, Václav Kubernát wrote:
> > Converting the driver to use regmap makes it more generic. It also makes
> > it a lot easier to debug through debugfs.
> >
> > Signed-off-by: Václav Kubernát <kubernat@xxxxxxxxx>
>
> Comments are in addition to comments from Dan and 0-day.
>
> > ---
> >  drivers/hwmon/Kconfig    |   1 +
> >  drivers/hwmon/max31790.c | 318 ++++++++++++++++++++-------------------
> >  2 files changed, 163 insertions(+), 156 deletions(-)
> >
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 54f04e61fb83..c2ec57672c4e 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -1092,6 +1092,7 @@ config SENSORS_MAX6697
> >  config SENSORS_MAX31790
> >       tristate "Maxim MAX31790 sensor chip"
> >       depends on I2C
> > +     select REGMAP_I2C
> >       help
> >         If you say yes here you get support for 6-Channel PWM-Output
> >         Fan RPM Controller.
> > diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
> > index 86e6c71db685..4e5add567890 100644
> > --- a/drivers/hwmon/max31790.c
> > +++ b/drivers/hwmon/max31790.c
> > @@ -12,6 +12,7 @@
> >  #include <linux/init.h>
> >  #include <linux/jiffies.h>
> >  #include <linux/module.h>
> > +#include <linux/regmap.h>
> >  #include <linux/slab.h>
> >
> >  /* MAX31790 registers */
> > @@ -46,92 +47,49 @@
> >
> >  #define NR_CHANNEL                   6
> >
> > +#define MAX31790_REG_USER_BYTE_67    0x67
> > +
> > +#define BULK_TO_U16(msb, lsb)                (((msb) << 8) + (lsb))
> > +#define U16_MSB(num)                 (((num) & 0xFF00) >> 8)
> > +#define U16_LSB(num)                 ((num) & 0x00FF)
> > +
> > +static const struct regmap_range max31790_ro_range = {
> > +     .range_min = MAX31790_REG_TACH_COUNT(0),
> > +     .range_max = MAX31790_REG_PWMOUT(0) - 1,
> > +};
> > +
> > +static const struct regmap_access_table max31790_wr_table = {
> > +     .no_ranges = &max31790_ro_range,
> > +     .n_no_ranges = 1,
> > +};
> > +
> > +static const struct regmap_range max31790_volatile_ranges[] = {
> > +     regmap_reg_range(MAX31790_REG_TACH_COUNT(0), MAX31790_REG_TACH_COUNT(12)),
> > +     regmap_reg_range(MAX31790_REG_FAN_FAULT_STATUS2, MAX31790_REG_FAN_FAULT_STATUS1),
> > +};
> > +
> > +static const struct regmap_access_table max31790_volatile_table = {
> > +     .no_ranges = max31790_volatile_ranges,
> > +     .n_no_ranges = 2,
> > +     .n_yes_ranges = 0
> > +};
> > +
> > +static const struct regmap_config max31790_regmap_config = {
> > +     .reg_bits = 8,
> > +     .val_bits = 8,
> > +     .reg_stride = 1,
> > +     .max_register = MAX31790_REG_USER_BYTE_67,
> > +     .wr_table = &max31790_wr_table,
> > +     .volatile_table = &max31790_volatile_table
> > +};
> > +
> >  /*
> >   * Client data (each client gets its own)
> >   */
> >  struct max31790_data {
> > -     struct i2c_client *client;
> > -     struct mutex update_lock;
> > -     bool valid; /* zero until following fields are valid */
> > -     unsigned long last_updated; /* in jiffies */
> > -
> > -     /* register values */
> > -     u8 fan_config[NR_CHANNEL];
> > -     u8 fan_dynamics[NR_CHANNEL];
> > -     u16 fault_status;
> > -     u16 tach[NR_CHANNEL * 2];
> > -     u16 pwm[NR_CHANNEL];
> > -     u16 target_count[NR_CHANNEL];
> > +     struct regmap *regmap;
> >  };
> >
> > -static struct max31790_data *max31790_update_device(struct device *dev)
> > -{
> > -     struct max31790_data *data = dev_get_drvdata(dev);
> > -     struct i2c_client *client = data->client;
> > -     struct max31790_data *ret = data;
> > -     int i;
> > -     int rv;
> > -
> > -     mutex_lock(&data->update_lock);
> > -
> > -     if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
> > -             rv = i2c_smbus_read_byte_data(client,
> > -                             MAX31790_REG_FAN_FAULT_STATUS1);
> > -             if (rv < 0)
> > -                     goto abort;
> > -             data->fault_status = rv & 0x3F;
> > -
> > -             rv = i2c_smbus_read_byte_data(client,
> > -                             MAX31790_REG_FAN_FAULT_STATUS2);
> > -             if (rv < 0)
> > -                     goto abort;
> > -             data->fault_status |= (rv & 0x3F) << 6;
> > -
> > -             for (i = 0; i < NR_CHANNEL; i++) {
> > -                     rv = i2c_smbus_read_word_swapped(client,
> > -                                     MAX31790_REG_TACH_COUNT(i));
> > -                     if (rv < 0)
> > -                             goto abort;
> > -                     data->tach[i] = rv;
> > -
> > -                     if (data->fan_config[i]
> > -                         & MAX31790_FAN_CFG_TACH_INPUT) {
> > -                             rv = i2c_smbus_read_word_swapped(client,
> > -                                     MAX31790_REG_TACH_COUNT(NR_CHANNEL
> > -                                                             + i));
> > -                             if (rv < 0)
> > -                                     goto abort;
> > -                             data->tach[NR_CHANNEL + i] = rv;
> > -                     } else {
> > -                             rv = i2c_smbus_read_word_swapped(client,
> > -                                             MAX31790_REG_PWMOUT(i));
> > -                             if (rv < 0)
> > -                                     goto abort;
> > -                             data->pwm[i] = rv;
> > -
> > -                             rv = i2c_smbus_read_word_swapped(client,
> > -                                             MAX31790_REG_TARGET_COUNT(i));
> > -                             if (rv < 0)
> > -                                     goto abort;
> > -                             data->target_count[i] = rv;
> > -                     }
> > -             }
> > -
> > -             data->last_updated = jiffies;
> > -             data->valid = true;
> > -     }
> > -     goto done;
> > -
> > -abort:
> > -     data->valid = false;
> > -     ret = ERR_PTR(rv);
> > -
> > -done:
> > -     mutex_unlock(&data->update_lock);
> > -
> > -     return ret;
> > -}
> > -
> >  static const u8 tach_period[8] = { 1, 2, 4, 8, 16, 32, 32, 32 };
> >
> >  static u8 get_tach_period(u8 fan_dynamics)
> > @@ -159,28 +117,89 @@ static u8 bits_for_tach_period(int rpm)
> >       return bits;
> >  }
> >
> > +static int read_reg_byte(struct regmap *regmap, u8 reg)
> > +{
> > +     int rv;
> > +     int val;
> > +
> > +     rv = regmap_read(regmap, reg, &val);
> > +
>
> lease no empty line between assignment and check.
>
> > +     if (rv < 0)
> > +             return rv;
> > +
> > +     return val;
> > +}
> > +
> > +static int read_reg_word(struct regmap *regmap, u8 reg)
> > +{
> > +     int rv;
> > +     u8 val_bulk[2];
> > +
> > +     rv = regmap_bulk_read(regmap, reg, val_bulk, 2);
> > +     if (rv < 0)
> > +             return rv;
> > +
> > +     return BULK_TO_U16(val_bulk[0], val_bulk[1]);
> > +}
> > +
> > +static int write_reg_word(struct regmap *regmap, u8 reg, u16 val)
> > +{
> > +     u8 bulk_val[2];
> > +
> > +     bulk_val[0] = U16_MSB(val);
> > +     bulk_val[1] = U16_LSB(val);
> > +
> > +     return regmap_bulk_write(regmap, reg, bulk_val, 2);
> > +}
> > +
> >  static int max31790_read_fan(struct device *dev, u32 attr, int channel,
> >                            long *val)
> >  {
> > -     struct max31790_data *data = max31790_update_device(dev);
> > -     int sr, rpm;
> > +     struct max31790_data *data = dev_get_drvdata(dev);
> > +     struct regmap *regmap = data->regmap;
> > +     int rpm, dynamics, tach, fault;
> >
> >       if (IS_ERR(data))
> >               return PTR_ERR(data);
>
> Now unnecessary.
>
> >
> >       switch (attr) {
> >       case hwmon_fan_input:
> > -             sr = get_tach_period(data->fan_dynamics[channel]);
> > -             rpm = RPM_FROM_REG(data->tach[channel], sr);
> > +             dynamics = read_reg_byte(regmap, MAX31790_REG_FAN_DYNAMICS(channel));
> > +             if (dynamics < 0)
> > +                     return dynamics;
> > +
> > +             tach = read_reg_word(regmap, MAX31790_REG_TACH_COUNT(channel));
> > +             if (tach < 0)
> > +                     return tach;
> > +
> > +             rpm = RPM_FROM_REG(tach, get_tach_period(dynamics));
> >               *val = rpm;
>
>                 *val = RPM_FROM_REG(tach, get_tach_period(dynamics));
>
> >               return 0;
> >       case hwmon_fan_target:
> > -             sr = get_tach_period(data->fan_dynamics[channel]);
> > -             rpm = RPM_FROM_REG(data->target_count[channel], sr);
> > +             dynamics = read_reg_byte(regmap, MAX31790_REG_FAN_DYNAMICS(channel));
> > +             if (dynamics < 0)
> > +                     return dynamics;
> > +
> > +             tach = read_reg_word(regmap, MAX31790_REG_TARGET_COUNT(channel));
> > +             if (tach < 0)
> > +                     return tach;
> > +
> > +             rpm = RPM_FROM_REG(tach, get_tach_period(dynamics));
> >               *val = rpm;
>
>                 *val = RPM_FROM_REG(tach, get_tach_period(dynamics));
>
> >               return 0;
> >       case hwmon_fan_fault:
> > -             *val = !!(data->fault_status & (1 << channel));
> > +             if (channel > 6)
> > +                     fault = read_reg_byte(regmap, MAX31790_REG_FAN_FAULT_STATUS2);
> > +             else
> > +                     fault = read_reg_byte(regmap, MAX31790_REG_FAN_FAULT_STATUS1);
> > +
> > +             if (fault < 0)
> > +                     return fault;
> > +
> > +             if (channel > 6)
> > +                     *val = !!(fault & (1 << (channel - 6)));
> > +             else
> > +                     *val = !!(fault & (1 << channel));
> >               return 0;
> >       default:
> >               return -EOPNOTSUPP;
> > @@ -191,52 +210,58 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
> >                             long val)
> >  {
> >       struct max31790_data *data = dev_get_drvdata(dev);
> > -     struct i2c_client *client = data->client;
> > +     struct regmap *regmap = data->regmap;
> >       int target_count;
> >       int err = 0;
> >       u8 bits;
> >       int sr;
> > -
> > -     mutex_lock(&data->update_lock);
> > +     int fan_dynamics;
> >
> >       switch (attr) {
> >       case hwmon_fan_target:
> >               val = clamp_val(val, FAN_RPM_MIN, FAN_RPM_MAX);
> >               bits = bits_for_tach_period(val);
> > -             data->fan_dynamics[channel] =
> > -                     ((data->fan_dynamics[channel] &
> > +             fan_dynamics = read_reg_byte(regmap, MAX31790_REG_FAN_DYNAMICS(channel));
> > +
> Unnecessary empty line.
>
> > +             if (fan_dynamics < 0)
> > +                     return fan_dynamics;
> > +
> > +             fan_dynamics =
> > +                     ((fan_dynamics &
> >                         ~MAX31790_FAN_DYN_SR_MASK) |
> >                        (bits << MAX31790_FAN_DYN_SR_SHIFT));
> > -             err = i2c_smbus_write_byte_data(client,
> > -                                     MAX31790_REG_FAN_DYNAMICS(channel),
> > -                                     data->fan_dynamics[channel]);
> > +             err = regmap_write(regmap,
> > +                                MAX31790_REG_FAN_DYNAMICS(channel),
> > +                                fan_dynamics);
> >               if (err < 0)
> >                       break;
> >
> > -             sr = get_tach_period(data->fan_dynamics[channel]);
> > +             sr = get_tach_period(fan_dynamics);
> >               target_count = RPM_TO_REG(val, sr);
> >               target_count = clamp_val(target_count, 0x1, 0x7FF);
> >
> > -             data->target_count[channel] = target_count << 5;
> > +             target_count = target_count << 5;
> >
> > -             err = i2c_smbus_write_word_swapped(client,
> > -                                     MAX31790_REG_TARGET_COUNT(channel),
> > -                                     data->target_count[channel]);
> > +             err = write_reg_word(regmap,
> > +                                  MAX31790_REG_TARGET_COUNT(channel),
> > +                                  target_count);
> >               break;
> >       default:
> >               err = -EOPNOTSUPP;
> >               break;
> >       }
> >
> > -     mutex_unlock(&data->update_lock);
> > -
> Why is this lock no longer required ? There are still multiple writes
> when writing hwmon_fan_target.
>
> >       return err;
> >  }
> >
> >  static umode_t max31790_fan_is_visible(const void *_data, u32 attr, int channel)
> >  {
> >       const struct max31790_data *data = _data;
> > -     u8 fan_config = data->fan_config[channel % NR_CHANNEL];
> > +     struct regmap *regmap = data->regmap;
> > +     u8 fan_config = read_reg_byte(regmap, MAX31790_REG_FAN_CONFIG(channel % NR_CHANNEL));
> > +
> > +     if (fan_config < 0)
> > +             return 0;
>
> fan_config needs to be int. Also, this is a poor way of handling
> this problem. Since fan_config does not change dynamically,
> this is one set of values that would make sense to keep cached
> locally.
>
> >
> >       switch (attr) {
> >       case hwmon_fan_input:
> > @@ -258,22 +283,29 @@ static umode_t max31790_fan_is_visible(const void *_data, u32 attr, int channel)
> >  static int max31790_read_pwm(struct device *dev, u32 attr, int channel,
> >                            long *val)
> >  {
> > -     struct max31790_data *data = max31790_update_device(dev);
> > -     u8 fan_config;
> > +     struct max31790_data *data = dev_get_drvdata(dev);
> > +     struct regmap *regmap = data->regmap;
> > +     int read;
> >
> >       if (IS_ERR(data))
> >               return PTR_ERR(data);
>
> Now unnecessary.
>
> >
> > -     fan_config = data->fan_config[channel];
> > -
> >       switch (attr) {
> >       case hwmon_pwm_input:
> > -             *val = data->pwm[channel] >> 8;
> > +             read = read_reg_word(regmap, MAX31790_REG_PWMOUT(channel));
> > +             if (read < 0)
> > +                     return read;
> > +
> > +             *val = read >> 8;
> >               return 0;
> >       case hwmon_pwm_enable:
> > -             if (fan_config & MAX31790_FAN_CFG_RPM_MODE)
> > +             read = read_reg_byte(regmap, MAX31790_REG_FAN_CONFIG(channel));
> > +             if (read < 0)
> > +                     return read;
> > +
> > +             if (read & MAX31790_FAN_CFG_RPM_MODE)
> >                       *val = 2;
> > -             else if (fan_config & MAX31790_FAN_CFG_TACH_INPUT_EN)
> > +             else if (read & MAX31790_FAN_CFG_TACH_INPUT_EN)
> >                       *val = 1;
> >               else
> >                       *val = 0;
> > @@ -287,25 +319,24 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel,
> >                             long val)
> >  {
> >       struct max31790_data *data = dev_get_drvdata(dev);
> > -     struct i2c_client *client = data->client;
> > +     struct regmap *regmap = data->regmap;
> >       u8 fan_config;
> >       int err = 0;
> >
> > -     mutex_lock(&data->update_lock);
> > -
> >       switch (attr) {
> >       case hwmon_pwm_input:
> >               if (val < 0 || val > 255) {
> >                       err = -EINVAL;
> >                       break;
> >               }
> > -             data->pwm[channel] = val << 8;
> > -             err = i2c_smbus_write_word_swapped(client,
> > -                                                MAX31790_REG_PWMOUT(channel),
> > -                                                data->pwm[channel]);
> > +             err = write_reg_word(regmap, MAX31790_REG_PWMOUT(channel), val << 8);
> >               break;
> >       case hwmon_pwm_enable:
> > -             fan_config = data->fan_config[channel];
> > +             fan_config = read_reg_byte(regmap, MAX31790_REG_FAN_CONFIG(channel % NR_CHANNEL));
> > +
> > +             if (fan_config < 0)
> > +                     return fan_config;
> > +
> >               if (val == 0) {
> >                       fan_config &= ~(MAX31790_FAN_CFG_TACH_INPUT_EN |
> >                                       MAX31790_FAN_CFG_RPM_MODE);
> > @@ -320,25 +351,26 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel,
> >                       err = -EINVAL;
> >                       break;
> >               }
> > -             data->fan_config[channel] = fan_config;
> > -             err = i2c_smbus_write_byte_data(client,
> > -                                     MAX31790_REG_FAN_CONFIG(channel),
> > -                                     fan_config);
> > +             err = regmap_write(regmap,
> > +                                MAX31790_REG_FAN_CONFIG(channel),
> > +                                fan_config);
> >               break;
> >       default:
> >               err = -EOPNOTSUPP;
> >               break;
> >       }
> >
> > -     mutex_unlock(&data->update_lock);
> > -
> Are you sure this mutex is no longer needed here, ie that there
> can not be an interaction with multiple writes from multiple processes
> at the same time ?
>
> >       return err;
> >  }
> >
> >  static umode_t max31790_pwm_is_visible(const void *_data, u32 attr, int channel)
> >  {
> >       const struct max31790_data *data = _data;
> > -     u8 fan_config = data->fan_config[channel];
> > +     struct regmap *regmap = data->regmap;
> > +     u8 fan_config = read_reg_byte(regmap, MAX31790_REG_FAN_CONFIG(channel % NR_CHANNEL));
> > +
> > +     if (fan_config < 0)
> > +             return 0;
>
> int problem again.
>
> >
> >       switch (attr) {
> >       case hwmon_pwm_input:
> > @@ -426,35 +458,12 @@ static const struct hwmon_chip_info max31790_chip_info = {
> >       .info = max31790_info,
> >  };
> >
> > -static int max31790_init_client(struct i2c_client *client,
> > -                             struct max31790_data *data)
> > -{
> > -     int i, rv;
> > -
> > -     for (i = 0; i < NR_CHANNEL; i++) {
> > -             rv = i2c_smbus_read_byte_data(client,
> > -                             MAX31790_REG_FAN_CONFIG(i));
> > -             if (rv < 0)
> > -                     return rv;
> > -             data->fan_config[i] = rv;
> > -
> > -             rv = i2c_smbus_read_byte_data(client,
> > -                             MAX31790_REG_FAN_DYNAMICS(i));
> > -             if (rv < 0)
> > -                     return rv;
> > -             data->fan_dynamics[i] = rv;
>
> The above "cached" values are static, and it did make sense to keep those
> locally to avoid requiring unnecessary error handling (and to detect issues
> with the chip early).
>
> > -     }
> > -
> > -     return 0;
> > -}
> > -
> >  static int max31790_probe(struct i2c_client *client)
> >  {
> >       struct i2c_adapter *adapter = client->adapter;
> >       struct device *dev = &client->dev;
> >       struct max31790_data *data;
> >       struct device *hwmon_dev;
> > -     int err;
> >
> >       if (!i2c_check_functionality(adapter,
> >                       I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA))
> > @@ -464,15 +473,12 @@ static int max31790_probe(struct i2c_client *client)
> >       if (!data)
> >               return -ENOMEM;
> >
> > -     data->client = client;
> > -     mutex_init(&data->update_lock);
> > +     data->regmap = devm_regmap_init_i2c(client, &max31790_regmap_config);
> >
> > -     /*
> > -      * Initialize the max31790 chip
> > -      */
> > -     err = max31790_init_client(client, data);
> > -     if (err)
> > -             return err;
> > +     if (IS_ERR(data->regmap)) {
> > +             dev_err(dev, "failed to allocate register map\n");
> > +             return PTR_ERR(data->regmap);
> > +     }
> >
> >       hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
> >                                                        data,

út 30. 3. 2021 v 0:27 odesílatel Guenter Roeck <linux@xxxxxxxxxxxx> napsal:
>
> On Tue, Mar 16, 2021 at 06:54:58PM +0100, Václav Kubernát wrote:
> > Converting the driver to use regmap makes it more generic. It also makes
> > it a lot easier to debug through debugfs.
> >
> > Signed-off-by: Václav Kubernát <kubernat@xxxxxxxxx>
>
> Comments are in addition to comments from Dan and 0-day.
>
> > ---
> >  drivers/hwmon/Kconfig    |   1 +
> >  drivers/hwmon/max31790.c | 318 ++++++++++++++++++++-------------------
> >  2 files changed, 163 insertions(+), 156 deletions(-)
> >
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 54f04e61fb83..c2ec57672c4e 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -1092,6 +1092,7 @@ config SENSORS_MAX6697
> >  config SENSORS_MAX31790
> >       tristate "Maxim MAX31790 sensor chip"
> >       depends on I2C
> > +     select REGMAP_I2C
> >       help
> >         If you say yes here you get support for 6-Channel PWM-Output
> >         Fan RPM Controller.
> > diff --git a/drivers/hwmon/max31790.c b/drivers/hwmon/max31790.c
> > index 86e6c71db685..4e5add567890 100644
> > --- a/drivers/hwmon/max31790.c
> > +++ b/drivers/hwmon/max31790.c
> > @@ -12,6 +12,7 @@
> >  #include <linux/init.h>
> >  #include <linux/jiffies.h>
> >  #include <linux/module.h>
> > +#include <linux/regmap.h>
> >  #include <linux/slab.h>
> >
> >  /* MAX31790 registers */
> > @@ -46,92 +47,49 @@
> >
> >  #define NR_CHANNEL                   6
> >
> > +#define MAX31790_REG_USER_BYTE_67    0x67
> > +
> > +#define BULK_TO_U16(msb, lsb)                (((msb) << 8) + (lsb))
> > +#define U16_MSB(num)                 (((num) & 0xFF00) >> 8)
> > +#define U16_LSB(num)                 ((num) & 0x00FF)
> > +
> > +static const struct regmap_range max31790_ro_range = {
> > +     .range_min = MAX31790_REG_TACH_COUNT(0),
> > +     .range_max = MAX31790_REG_PWMOUT(0) - 1,
> > +};
> > +
> > +static const struct regmap_access_table max31790_wr_table = {
> > +     .no_ranges = &max31790_ro_range,
> > +     .n_no_ranges = 1,
> > +};
> > +
> > +static const struct regmap_range max31790_volatile_ranges[] = {
> > +     regmap_reg_range(MAX31790_REG_TACH_COUNT(0), MAX31790_REG_TACH_COUNT(12)),
> > +     regmap_reg_range(MAX31790_REG_FAN_FAULT_STATUS2, MAX31790_REG_FAN_FAULT_STATUS1),
> > +};
> > +
> > +static const struct regmap_access_table max31790_volatile_table = {
> > +     .no_ranges = max31790_volatile_ranges,
> > +     .n_no_ranges = 2,
> > +     .n_yes_ranges = 0
> > +};
> > +
> > +static const struct regmap_config max31790_regmap_config = {
> > +     .reg_bits = 8,
> > +     .val_bits = 8,
> > +     .reg_stride = 1,
> > +     .max_register = MAX31790_REG_USER_BYTE_67,
> > +     .wr_table = &max31790_wr_table,
> > +     .volatile_table = &max31790_volatile_table
> > +};
> > +
> >  /*
> >   * Client data (each client gets its own)
> >   */
> >  struct max31790_data {
> > -     struct i2c_client *client;
> > -     struct mutex update_lock;
> > -     bool valid; /* zero until following fields are valid */
> > -     unsigned long last_updated; /* in jiffies */
> > -
> > -     /* register values */
> > -     u8 fan_config[NR_CHANNEL];
> > -     u8 fan_dynamics[NR_CHANNEL];
> > -     u16 fault_status;
> > -     u16 tach[NR_CHANNEL * 2];
> > -     u16 pwm[NR_CHANNEL];
> > -     u16 target_count[NR_CHANNEL];
> > +     struct regmap *regmap;
> >  };
> >
> > -static struct max31790_data *max31790_update_device(struct device *dev)
> > -{
> > -     struct max31790_data *data = dev_get_drvdata(dev);
> > -     struct i2c_client *client = data->client;
> > -     struct max31790_data *ret = data;
> > -     int i;
> > -     int rv;
> > -
> > -     mutex_lock(&data->update_lock);
> > -
> > -     if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
> > -             rv = i2c_smbus_read_byte_data(client,
> > -                             MAX31790_REG_FAN_FAULT_STATUS1);
> > -             if (rv < 0)
> > -                     goto abort;
> > -             data->fault_status = rv & 0x3F;
> > -
> > -             rv = i2c_smbus_read_byte_data(client,
> > -                             MAX31790_REG_FAN_FAULT_STATUS2);
> > -             if (rv < 0)
> > -                     goto abort;
> > -             data->fault_status |= (rv & 0x3F) << 6;
> > -
> > -             for (i = 0; i < NR_CHANNEL; i++) {
> > -                     rv = i2c_smbus_read_word_swapped(client,
> > -                                     MAX31790_REG_TACH_COUNT(i));
> > -                     if (rv < 0)
> > -                             goto abort;
> > -                     data->tach[i] = rv;
> > -
> > -                     if (data->fan_config[i]
> > -                         & MAX31790_FAN_CFG_TACH_INPUT) {
> > -                             rv = i2c_smbus_read_word_swapped(client,
> > -                                     MAX31790_REG_TACH_COUNT(NR_CHANNEL
> > -                                                             + i));
> > -                             if (rv < 0)
> > -                                     goto abort;
> > -                             data->tach[NR_CHANNEL + i] = rv;
> > -                     } else {
> > -                             rv = i2c_smbus_read_word_swapped(client,
> > -                                             MAX31790_REG_PWMOUT(i));
> > -                             if (rv < 0)
> > -                                     goto abort;
> > -                             data->pwm[i] = rv;
> > -
> > -                             rv = i2c_smbus_read_word_swapped(client,
> > -                                             MAX31790_REG_TARGET_COUNT(i));
> > -                             if (rv < 0)
> > -                                     goto abort;
> > -                             data->target_count[i] = rv;
> > -                     }
> > -             }
> > -
> > -             data->last_updated = jiffies;
> > -             data->valid = true;
> > -     }
> > -     goto done;
> > -
> > -abort:
> > -     data->valid = false;
> > -     ret = ERR_PTR(rv);
> > -
> > -done:
> > -     mutex_unlock(&data->update_lock);
> > -
> > -     return ret;
> > -}
> > -
> >  static const u8 tach_period[8] = { 1, 2, 4, 8, 16, 32, 32, 32 };
> >
> >  static u8 get_tach_period(u8 fan_dynamics)
> > @@ -159,28 +117,89 @@ static u8 bits_for_tach_period(int rpm)
> >       return bits;
> >  }
> >
> > +static int read_reg_byte(struct regmap *regmap, u8 reg)
> > +{
> > +     int rv;
> > +     int val;
> > +
> > +     rv = regmap_read(regmap, reg, &val);
> > +
>
> lease no empty line between assignment and check.
>
> > +     if (rv < 0)
> > +             return rv;
> > +
> > +     return val;
> > +}
> > +
> > +static int read_reg_word(struct regmap *regmap, u8 reg)
> > +{
> > +     int rv;
> > +     u8 val_bulk[2];
> > +
> > +     rv = regmap_bulk_read(regmap, reg, val_bulk, 2);
> > +     if (rv < 0)
> > +             return rv;
> > +
> > +     return BULK_TO_U16(val_bulk[0], val_bulk[1]);
> > +}
> > +
> > +static int write_reg_word(struct regmap *regmap, u8 reg, u16 val)
> > +{
> > +     u8 bulk_val[2];
> > +
> > +     bulk_val[0] = U16_MSB(val);
> > +     bulk_val[1] = U16_LSB(val);
> > +
> > +     return regmap_bulk_write(regmap, reg, bulk_val, 2);
> > +}
> > +
> >  static int max31790_read_fan(struct device *dev, u32 attr, int channel,
> >                            long *val)
> >  {
> > -     struct max31790_data *data = max31790_update_device(dev);
> > -     int sr, rpm;
> > +     struct max31790_data *data = dev_get_drvdata(dev);
> > +     struct regmap *regmap = data->regmap;
> > +     int rpm, dynamics, tach, fault;
> >
> >       if (IS_ERR(data))
> >               return PTR_ERR(data);
>
> Now unnecessary.
>
> >
> >       switch (attr) {
> >       case hwmon_fan_input:
> > -             sr = get_tach_period(data->fan_dynamics[channel]);
> > -             rpm = RPM_FROM_REG(data->tach[channel], sr);
> > +             dynamics = read_reg_byte(regmap, MAX31790_REG_FAN_DYNAMICS(channel));
> > +             if (dynamics < 0)
> > +                     return dynamics;
> > +
> > +             tach = read_reg_word(regmap, MAX31790_REG_TACH_COUNT(channel));
> > +             if (tach < 0)
> > +                     return tach;
> > +
> > +             rpm = RPM_FROM_REG(tach, get_tach_period(dynamics));
> >               *val = rpm;
>
>                 *val = RPM_FROM_REG(tach, get_tach_period(dynamics));
>
> >               return 0;
> >       case hwmon_fan_target:
> > -             sr = get_tach_period(data->fan_dynamics[channel]);
> > -             rpm = RPM_FROM_REG(data->target_count[channel], sr);
> > +             dynamics = read_reg_byte(regmap, MAX31790_REG_FAN_DYNAMICS(channel));
> > +             if (dynamics < 0)
> > +                     return dynamics;
> > +
> > +             tach = read_reg_word(regmap, MAX31790_REG_TARGET_COUNT(channel));
> > +             if (tach < 0)
> > +                     return tach;
> > +
> > +             rpm = RPM_FROM_REG(tach, get_tach_period(dynamics));
> >               *val = rpm;
>
>                 *val = RPM_FROM_REG(tach, get_tach_period(dynamics));
>
> >               return 0;
> >       case hwmon_fan_fault:
> > -             *val = !!(data->fault_status & (1 << channel));
> > +             if (channel > 6)
> > +                     fault = read_reg_byte(regmap, MAX31790_REG_FAN_FAULT_STATUS2);
> > +             else
> > +                     fault = read_reg_byte(regmap, MAX31790_REG_FAN_FAULT_STATUS1);
> > +
> > +             if (fault < 0)
> > +                     return fault;
> > +
> > +             if (channel > 6)
> > +                     *val = !!(fault & (1 << (channel - 6)));
> > +             else
> > +                     *val = !!(fault & (1 << channel));
> >               return 0;
> >       default:
> >               return -EOPNOTSUPP;
> > @@ -191,52 +210,58 @@ static int max31790_write_fan(struct device *dev, u32 attr, int channel,
> >                             long val)
> >  {
> >       struct max31790_data *data = dev_get_drvdata(dev);
> > -     struct i2c_client *client = data->client;
> > +     struct regmap *regmap = data->regmap;
> >       int target_count;
> >       int err = 0;
> >       u8 bits;
> >       int sr;
> > -
> > -     mutex_lock(&data->update_lock);
> > +     int fan_dynamics;
> >
> >       switch (attr) {
> >       case hwmon_fan_target:
> >               val = clamp_val(val, FAN_RPM_MIN, FAN_RPM_MAX);
> >               bits = bits_for_tach_period(val);
> > -             data->fan_dynamics[channel] =
> > -                     ((data->fan_dynamics[channel] &
> > +             fan_dynamics = read_reg_byte(regmap, MAX31790_REG_FAN_DYNAMICS(channel));
> > +
> Unnecessary empty line.
>
> > +             if (fan_dynamics < 0)
> > +                     return fan_dynamics;
> > +
> > +             fan_dynamics =
> > +                     ((fan_dynamics &
> >                         ~MAX31790_FAN_DYN_SR_MASK) |
> >                        (bits << MAX31790_FAN_DYN_SR_SHIFT));
> > -             err = i2c_smbus_write_byte_data(client,
> > -                                     MAX31790_REG_FAN_DYNAMICS(channel),
> > -                                     data->fan_dynamics[channel]);
> > +             err = regmap_write(regmap,
> > +                                MAX31790_REG_FAN_DYNAMICS(channel),
> > +                                fan_dynamics);
> >               if (err < 0)
> >                       break;
> >
> > -             sr = get_tach_period(data->fan_dynamics[channel]);
> > +             sr = get_tach_period(fan_dynamics);
> >               target_count = RPM_TO_REG(val, sr);
> >               target_count = clamp_val(target_count, 0x1, 0x7FF);
> >
> > -             data->target_count[channel] = target_count << 5;
> > +             target_count = target_count << 5;
> >
> > -             err = i2c_smbus_write_word_swapped(client,
> > -                                     MAX31790_REG_TARGET_COUNT(channel),
> > -                                     data->target_count[channel]);
> > +             err = write_reg_word(regmap,
> > +                                  MAX31790_REG_TARGET_COUNT(channel),
> > +                                  target_count);
> >               break;
> >       default:
> >               err = -EOPNOTSUPP;
> >               break;
> >       }
> >
> > -     mutex_unlock(&data->update_lock);
> > -
> Why is this lock no longer required ? There are still multiple writes
> when writing hwmon_fan_target.
>
> >       return err;
> >  }
> >
> >  static umode_t max31790_fan_is_visible(const void *_data, u32 attr, int channel)
> >  {
> >       const struct max31790_data *data = _data;
> > -     u8 fan_config = data->fan_config[channel % NR_CHANNEL];
> > +     struct regmap *regmap = data->regmap;
> > +     u8 fan_config = read_reg_byte(regmap, MAX31790_REG_FAN_CONFIG(channel % NR_CHANNEL));
> > +
> > +     if (fan_config < 0)
> > +             return 0;
>
> fan_config needs to be int. Also, this is a poor way of handling
> this problem. Since fan_config does not change dynamically,
> this is one set of values that would make sense to keep cached
> locally.
>
> >
> >       switch (attr) {
> >       case hwmon_fan_input:
> > @@ -258,22 +283,29 @@ static umode_t max31790_fan_is_visible(const void *_data, u32 attr, int channel)
> >  static int max31790_read_pwm(struct device *dev, u32 attr, int channel,
> >                            long *val)
> >  {
> > -     struct max31790_data *data = max31790_update_device(dev);
> > -     u8 fan_config;
> > +     struct max31790_data *data = dev_get_drvdata(dev);
> > +     struct regmap *regmap = data->regmap;
> > +     int read;
> >
> >       if (IS_ERR(data))
> >               return PTR_ERR(data);
>
> Now unnecessary.
>
> >
> > -     fan_config = data->fan_config[channel];
> > -
> >       switch (attr) {
> >       case hwmon_pwm_input:
> > -             *val = data->pwm[channel] >> 8;
> > +             read = read_reg_word(regmap, MAX31790_REG_PWMOUT(channel));
> > +             if (read < 0)
> > +                     return read;
> > +
> > +             *val = read >> 8;
> >               return 0;
> >       case hwmon_pwm_enable:
> > -             if (fan_config & MAX31790_FAN_CFG_RPM_MODE)
> > +             read = read_reg_byte(regmap, MAX31790_REG_FAN_CONFIG(channel));
> > +             if (read < 0)
> > +                     return read;
> > +
> > +             if (read & MAX31790_FAN_CFG_RPM_MODE)
> >                       *val = 2;
> > -             else if (fan_config & MAX31790_FAN_CFG_TACH_INPUT_EN)
> > +             else if (read & MAX31790_FAN_CFG_TACH_INPUT_EN)
> >                       *val = 1;
> >               else
> >                       *val = 0;
> > @@ -287,25 +319,24 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel,
> >                             long val)
> >  {
> >       struct max31790_data *data = dev_get_drvdata(dev);
> > -     struct i2c_client *client = data->client;
> > +     struct regmap *regmap = data->regmap;
> >       u8 fan_config;
> >       int err = 0;
> >
> > -     mutex_lock(&data->update_lock);
> > -
> >       switch (attr) {
> >       case hwmon_pwm_input:
> >               if (val < 0 || val > 255) {
> >                       err = -EINVAL;
> >                       break;
> >               }
> > -             data->pwm[channel] = val << 8;
> > -             err = i2c_smbus_write_word_swapped(client,
> > -                                                MAX31790_REG_PWMOUT(channel),
> > -                                                data->pwm[channel]);
> > +             err = write_reg_word(regmap, MAX31790_REG_PWMOUT(channel), val << 8);
> >               break;
> >       case hwmon_pwm_enable:
> > -             fan_config = data->fan_config[channel];
> > +             fan_config = read_reg_byte(regmap, MAX31790_REG_FAN_CONFIG(channel % NR_CHANNEL));
> > +
> > +             if (fan_config < 0)
> > +                     return fan_config;
> > +
> >               if (val == 0) {
> >                       fan_config &= ~(MAX31790_FAN_CFG_TACH_INPUT_EN |
> >                                       MAX31790_FAN_CFG_RPM_MODE);
> > @@ -320,25 +351,26 @@ static int max31790_write_pwm(struct device *dev, u32 attr, int channel,
> >                       err = -EINVAL;
> >                       break;
> >               }
> > -             data->fan_config[channel] = fan_config;
> > -             err = i2c_smbus_write_byte_data(client,
> > -                                     MAX31790_REG_FAN_CONFIG(channel),
> > -                                     fan_config);
> > +             err = regmap_write(regmap,
> > +                                MAX31790_REG_FAN_CONFIG(channel),
> > +                                fan_config);
> >               break;
> >       default:
> >               err = -EOPNOTSUPP;
> >               break;
> >       }
> >
> > -     mutex_unlock(&data->update_lock);
> > -
> Are you sure this mutex is no longer needed here, ie that there
> can not be an interaction with multiple writes from multiple processes
> at the same time ?
>
> >       return err;
> >  }
> >
> >  static umode_t max31790_pwm_is_visible(const void *_data, u32 attr, int channel)
> >  {
> >       const struct max31790_data *data = _data;
> > -     u8 fan_config = data->fan_config[channel];
> > +     struct regmap *regmap = data->regmap;
> > +     u8 fan_config = read_reg_byte(regmap, MAX31790_REG_FAN_CONFIG(channel % NR_CHANNEL));
> > +
> > +     if (fan_config < 0)
> > +             return 0;
>
> int problem again.
>
> >
> >       switch (attr) {
> >       case hwmon_pwm_input:
> > @@ -426,35 +458,12 @@ static const struct hwmon_chip_info max31790_chip_info = {
> >       .info = max31790_info,
> >  };
> >
> > -static int max31790_init_client(struct i2c_client *client,
> > -                             struct max31790_data *data)
> > -{
> > -     int i, rv;
> > -
> > -     for (i = 0; i < NR_CHANNEL; i++) {
> > -             rv = i2c_smbus_read_byte_data(client,
> > -                             MAX31790_REG_FAN_CONFIG(i));
> > -             if (rv < 0)
> > -                     return rv;
> > -             data->fan_config[i] = rv;
> > -
> > -             rv = i2c_smbus_read_byte_data(client,
> > -                             MAX31790_REG_FAN_DYNAMICS(i));
> > -             if (rv < 0)
> > -                     return rv;
> > -             data->fan_dynamics[i] = rv;
>
> The above "cached" values are static, and it did make sense to keep those
> locally to avoid requiring unnecessary error handling (and to detect issues
> with the chip early).
>
> > -     }
> > -
> > -     return 0;
> > -}
> > -
> >  static int max31790_probe(struct i2c_client *client)
> >  {
> >       struct i2c_adapter *adapter = client->adapter;
> >       struct device *dev = &client->dev;
> >       struct max31790_data *data;
> >       struct device *hwmon_dev;
> > -     int err;
> >
> >       if (!i2c_check_functionality(adapter,
> >                       I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA))
> > @@ -464,15 +473,12 @@ static int max31790_probe(struct i2c_client *client)
> >       if (!data)
> >               return -ENOMEM;
> >
> > -     data->client = client;
> > -     mutex_init(&data->update_lock);
> > +     data->regmap = devm_regmap_init_i2c(client, &max31790_regmap_config);
> >
> > -     /*
> > -      * Initialize the max31790 chip
> > -      */
> > -     err = max31790_init_client(client, data);
> > -     if (err)
> > -             return err;
> > +     if (IS_ERR(data->regmap)) {
> > +             dev_err(dev, "failed to allocate register map\n");
> > +             return PTR_ERR(data->regmap);
> > +     }
> >
> >       hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
> >                                                        data,