-----Original Message----- From: Guenter Roeck <groeck7@xxxxxxxxx> On Behalf Of Guenter Roeck Sent: Thursday, May 4, 2023 4:22 PM To: Matyas, Daniel <Daniel.Matyas@xxxxxxxxxx> Cc: Jean Delvare <jdelvare@xxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; Krzysztof Kozlowski <krzysztof.kozlowski+dt@xxxxxxxxxx>; Jonathan Corbet <corbet@xxxxxxx>; linux-hwmon@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-doc@xxxxxxxxxxxxxxx Subject: Re: [PATCH v4 2/2] hwmon: max31827: add MAX31827 driver [External] On 5/4/23 02:39, Daniel Matyas wrote: > MAX31827 is a low-power temperature switch with I2C interface. > > The device is a ±1°C accuracy from -40°C to +125°C > (12 bits) local temperature switch and sensor with I2C/SM- Bus > interface. The combination of small 6-bump wafer-lev- el package (WLP) > and high accuracy makes this temper- ature sensor/switch ideal for a > wide range of applications. > > Signed-off-by: Daniel Matyas <daniel.matyas@xxxxxxxxxx> Thanks to missing change log, this review is incomplete and just mentions a few obvious problems. Should I write the changelog as a cover letter or should I just add it at the end of the usual commit message? > --- > Documentation/hwmon/index.rst | 1 + > Documentation/hwmon/max31827.rst | 83 ++++++ > MAINTAINERS | 2 + > drivers/hwmon/Kconfig | 11 + > drivers/hwmon/Makefile | 2 +- > drivers/hwmon/max31827.c | 428 +++++++++++++++++++++++++++++++ > 6 files changed, 526 insertions(+), 1 deletion(-) > create mode 100644 Documentation/hwmon/max31827.rst > create mode 100644 drivers/hwmon/max31827.c > > diff --git a/Documentation/hwmon/index.rst > b/Documentation/hwmon/index.rst index f1fe75f596a5..965a830ea766 > 100644 > --- a/Documentation/hwmon/index.rst > +++ b/Documentation/hwmon/index.rst > @@ -139,6 +139,7 @@ Hardware Monitoring Kernel Drivers > max31760 > max31785 > max31790 > + max31827 > max34440 > max6620 > max6639 > diff --git a/Documentation/hwmon/max31827.rst > b/Documentation/hwmon/max31827.rst > new file mode 100644 > index 000000000000..5b94ad62baa3 > --- /dev/null > +++ b/Documentation/hwmon/max31827.rst > @@ -0,0 +1,83 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +Kernel driver max31827 > +====================== > + > +Supported chips: > + > + * Maxim MAX31827 > + > + Prefix: 'max31827' > + > + Addresses scanned: I2C 0x40 - 0x5f > + > + Datasheet: Publicly available at the Analog Devices website > + > + * Maxim MAX31828 > + > + Prefix: 'max31828' > + > + Addresses scanned: I2C 0x40 - 0x5f > + > + Datasheet: Publicly available at the Analog Devices website > + > + * Maxim MAX31829 > + > + Prefix: 'max31829' > + > + Addresses scanned: I2C 0x40 - 0x5f > + > + Datasheet: Publicly available at the Analog Devices website > + > + > +Authors: > + - Daniel Matyas <daniel.matyas@xxxxxxxxxx> > + > +Description > +----------- > + > +The chips supported by this driver are quite similar. The only > +difference between them is found in the default power-on behaviour of > +the chips. While the MAX31827's fault queue is set to 1, the other > +two chip's fault queue is set to 4. Besides this, the MAX31829's > +alarm active state is high, while the other two chip's alarms are > +active on low. It is important to note that the chips can be > +configured to operate in the same manner with 1 write operation to > +the configuration register. From here on, we will refer to all these chips as MAX31827. > + > +MAX31827 implements a temperature sensor with a 6 WLP packaging > +scheme. This sensor measures the temperature of the chip itself. > + > +MAX31827 has low and over temperature alarms with an effective value > +and a hysteresis value: -40 and -30 degrees for under temperature > +alarm and +100 and > ++90 degrees for over temperature alarm. > + > +The alarm can be configured in comparator and interrupt mode. > +Currently only comparator mode is implemented. In Comparator mode, > +the OT/UT status bits have a value of 1 when the temperature rises > +above the TH value or falls below TL, which is also subject to the > +Fault Queue selection. OT status returns to 0 when the temperature drops below the TH_HYST value or when shutdown mode is entered. > +Similarly, UT status returns to 0 when the temperature rises above > +TL_HYST value or when shutdown mode is entered. > + > +Putting the MAX31827 into shutdown mode also resets the OT/UT status > +bits. Note that if the mode is changed while OT/UT status bits are > +set, an OT/UT status reset may be required before it begins to behave > +normally. To prevent this, it is recommended to perform a read of the > +configuration/status register to clear the status bits before changing the operating mode. > + > +The conversions can be manual with the one-shot functionality and > +automatic with a set frequency. When powered on, the chip measures temperatures with 1 conv/s. > +Enabling the device when it is already enabled has the side effect of > +setting the conversion frequency to 1 conv/s. The conversion time > +varies depending on the resolution. The conversion time doubles with > +every bit of increased resolution. For 10 bit resolution 35ms are > +needed, while for 12 bit resolution > +(default) 140ms. When chip is in shutdown mode and a read operation > +is requested, one-shot is triggered, the device waits for 140 > +(conversion time) + 1 > +(error) ms, and only after that is the temperature value register read. > + > +Notes > +----- > + > +Currently fault queue, alarm polarity and resolution cannot be modified. > +PEC is not implemented either. > diff --git a/MAINTAINERS b/MAINTAINERS index > 0997a0490c97..fabc8869b13b 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -12541,6 +12541,8 @@ L: linux-hwmon@xxxxxxxxxxxxxxx > S: Supported > W: http://ez.analog.com/community/linux-device-drivers > F: Documentation/devicetree/bindings/hwmon/adi,max31827.yaml > +F: Documentation/hwmon/max31827.rst > +F: drivers/hwmon/max31827.c > > MAX6650 HARDWARE MONITOR AND FAN CONTROLLER DRIVER > L: linux-hwmon@xxxxxxxxxxxxxxx > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig index > 5b3b76477b0e..1e8546b3a8f2 100644 > --- a/drivers/hwmon/Kconfig > +++ b/drivers/hwmon/Kconfig > @@ -1097,6 +1097,17 @@ config SENSORS_MAX31760 > This driver can also be built as a module. If so, the module > will be called max31760. > > +config MAX31827 > + tristate "MAX31827 low-power temperature switch and similar devices" > + depends on I2C > + select REGMAP_I2C > + help > + If you say yes here you get support for MAX31827, MAX31828 and > + MAX31829 low-power temperature switches and sensors connected with I2C. > + > + This driver can also be built as a module. If so, the module > + will be called max31827. > + > config SENSORS_MAX6620 > tristate "Maxim MAX6620 fan controller" > depends on I2C > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile index > 88712b5031c8..dfb9aaf979bb 100644 > --- a/drivers/hwmon/Makefile > +++ b/drivers/hwmon/Makefile > @@ -149,6 +149,7 @@ obj-$(CONFIG_SENSORS_MAX6642) += max6642.o > obj-$(CONFIG_SENSORS_MAX6650) += max6650.o > obj-$(CONFIG_SENSORS_MAX6697) += max6697.o > obj-$(CONFIG_SENSORS_MAX31790) += max31790.o > +obj-$(CONFIG_MAX31827) += max31827.o > obj-$(CONFIG_SENSORS_MC13783_ADC)+= mc13783-adc.o > obj-$(CONFIG_SENSORS_MC34VR500) += mc34vr500.o > obj-$(CONFIG_SENSORS_MCP3021) += mcp3021.o > @@ -223,4 +224,3 @@ obj-$(CONFIG_SENSORS_PECI) += peci/ > obj-$(CONFIG_PMBUS) += pmbus/ > > ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG > - > diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c new > file mode 100644 index 000000000000..48ab62f76f7b > --- /dev/null > +++ b/drivers/hwmon/max31827.c > @@ -0,0 +1,428 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * max31827.c - Support for Maxim Low-Power Switch > + * > + * Copyright (c) 2023 Daniel Matyas <daniel.matyas@xxxxxxxxxx> */ > + > +#include <linux/bitfield.h> > +#include <linux/delay.h> > +#include <linux/hwmon.h> > +#include <linux/i2c.h> > +#include <linux/mutex.h> > +#include <linux/regmap.h> > + > +#define MAX31827_T_REG 0x0 > +#define MAX31827_CONFIGURATION_REG 0x2 > +#define MAX31827_TH_REG 0x4 > +#define MAX31827_TL_REG 0x6 > +#define MAX31827_TH_HYST_REG 0x8 > +#define MAX31827_TL_HYST_REG 0xA > + > +#define MAX31827_CONFIGURATION_1SHOT_MASK BIT(0) > +#define MAX31827_CONFIGURATION_CNV_RATE_MASK GENMASK(3, 1) > +#define MAX31827_CONFIGURATION_U_TEMP_STAT_MASK BIT(14) #define > +MAX31827_CONFIGURATION_O_TEMP_STAT_MASK BIT(15) > + > +#define MAX31827_12_BIT_CNV_TIME 141 > + > +#define MAX31827_CNV_1_DIV_64_HZ 0x1 > +#define MAX31827_CNV_1_DIV_32_HZ 0x2 > +#define MAX31827_CNV_1_DIV_16_HZ 0x3 > +#define MAX31827_CNV_1_DIV_4_HZ 0x4 > +#define MAX31827_CNV_1_HZ 0x5 > +#define MAX31827_CNV_4_HZ 0x6 > +#define MAX31827_CNV_8_HZ 0x7 > + > +#define LONG_MASK 0xFFFFFFFFFFFFFFFF > + This would be ULLONG_MAX, but I don't really see .. > +#define MAX31827_16_BIT_TO_M_DGR(x) ((long)(~(~(x) & LONG_MASK)) * 1000 >> 4) ... the point here. Masking anything against 0xFFFFFFFFFFFFFFFF doesn't do any good, and the register values are really 13 bit wide with the upper 4 bit reflecting the sign. Using one of the sign_extend() variants would be more appropriate to calculate the temperature. I also don't understand the shift since temperature values are supposedly - per datasheet - aligned to bit 0. > +#define MAX31827_M_DGR_TO_16_BIT(x) (((x) << 4) / 1000) Same here. This seems to drop the lower 4 temperature bits (fractions) for no good reason. I am doing the shift, because the value of LSB is not 1, but 0.0625. Thus, I am dividing by 16 (>> 4) when converting to milli-degrees, and I am multiplying by 16 (<< 4), when converting to 16 bit format. > +#define MAX31827_DEVICE_ENABLE(x) ((x) ? 0xA : 0x0) > + > +struct max31827_state { > + /* > + * Prevent simultaneous access to the i2c client. > + */ > + struct mutex lock; > + struct regmap *regmap; > + bool enable; > +}; > + > +static const struct regmap_config max31827_regmap = { > + .reg_bits = 8, > + .val_bits = 16, > + .max_register = 0xA, > +}; > + > +static int write_alarm_val(struct max31827_state *st, unsigned int reg, > + long val) > +{ > + unsigned int cfg; > + unsigned int tmp; > + int ret; > + > + val = MAX31827_M_DGR_TO_16_BIT(val); > + > + /* > + * Before the Temperature Threshold Alarm and Alarm Hysteresis Threshold > + * register values are changed over I2C, the part must be in shutdown > + * mode. > + * > + * Mutex is used to ensure, that some other process doesn't change the > + * configuration register. > + */ > + mutex_lock(&st->lock); > + > + if (!st->enable) > + return regmap_write(st->regmap, reg, val); > + Hang guaranteed here. > + ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &cfg); > + if (ret) > + return ret; ... and here and everywhere else where the function returns without releasing the mutex. > + > + tmp = cfg & ~(MAX31827_CONFIGURATION_1SHOT_MASK | > + MAX31827_CONFIGURATION_CNV_RATE_MASK); > + ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, tmp); > + if (ret) > + return ret; > + > + ret = regmap_write(st->regmap, reg, val); > + if (ret) > + return ret; > + > + ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, cfg); > + > + mutex_unlock(&st->lock); > + > + return ret; > +} > + > +static umode_t max31827_is_visible(const void *state, > + enum hwmon_sensor_types type, u32 attr, > + int channel) > +{ > + if (type == hwmon_temp) { > + switch (attr) { > + case hwmon_temp_enable: > + case hwmon_temp_max: > + case hwmon_temp_min: > + case hwmon_temp_max_hyst: > + case hwmon_temp_min_hyst: > + return 0644; > + case hwmon_temp_input: > + case hwmon_temp_min_alarm: > + case hwmon_temp_max_alarm: > + return 0444; > + default: > + return 0; > + } > + } else if (type == hwmon_chip) { > + if (attr == hwmon_chip_update_interval) > + return 0644; > + } > + > + return 0; > +} > + > +static int max31827_read(struct device *dev, enum hwmon_sensor_types type, > + u32 attr, int channel, long *val) { > + struct max31827_state *st = dev_get_drvdata(dev); > + unsigned int uval; > + int ret; > + > + switch (type) { > + case hwmon_temp: > + switch (attr) { > + case hwmon_temp_enable: > + ret = regmap_read(st->regmap, > + MAX31827_CONFIGURATION_REG, &uval); > + uval = FIELD_GET(MAX31827_CONFIGURATION_1SHOT_MASK | > + MAX31827_CONFIGURATION_CNV_RATE_MASK, > + uval); > + *val = !!uval; > + > + break; > + case hwmon_temp_input: > + mutex_lock(&st->lock); > + > + if (!st->enable) { > + /* > + * This operation requires mutex protection, > + * because the chip configuration should not > + * be changed during the conversion process. > + */ > + > + ret = regmap_update_bits(st->regmap, > + MAX31827_CONFIGURATION_REG, > + MAX31827_CONFIGURATION_1SHOT_MASK, > + 1); > + if (ret) > + return ret; Another hang due to lacking mutex_unlock(). > + > + msleep(MAX31827_12_BIT_CNV_TIME); > + } > + ret = regmap_read(st->regmap, MAX31827_T_REG, &uval); > + > + mutex_unlock(&st->lock); > + > + *val = MAX31827_16_BIT_TO_M_DGR(uval); > + > + break; > + case hwmon_temp_max: > + ret = regmap_read(st->regmap, MAX31827_TH_REG, &uval); > + *val = MAX31827_16_BIT_TO_M_DGR(uval); > + break; > + case hwmon_temp_max_hyst: > + ret = regmap_read(st->regmap, MAX31827_TH_HYST_REG, > + &uval); > + *val = MAX31827_16_BIT_TO_M_DGR(uval); > + break; > + case hwmon_temp_max_alarm: > + ret = regmap_read(st->regmap, > + MAX31827_CONFIGURATION_REG, &uval); > + *val = FIELD_GET(MAX31827_CONFIGURATION_O_TEMP_STAT_MASK, > + uval); > + break; > + case hwmon_temp_min: > + ret = regmap_read(st->regmap, MAX31827_TL_REG, &uval); > + *val = MAX31827_16_BIT_TO_M_DGR(uval); > + break; > + case hwmon_temp_min_hyst: > + ret = regmap_read(st->regmap, MAX31827_TL_HYST_REG, > + &uval); > + *val = MAX31827_16_BIT_TO_M_DGR(uval); > + break; > + case hwmon_temp_min_alarm: > + ret = regmap_read(st->regmap, > + MAX31827_CONFIGURATION_REG, &uval); > + *val = FIELD_GET(MAX31827_CONFIGURATION_U_TEMP_STAT_MASK, > + uval); > + break; > + default: > + ret = -EOPNOTSUPP; > + break; > + } > + > + break; > + > + case hwmon_chip: > + if (attr == hwmon_chip_update_interval) { > + ret = regmap_read(st->regmap, > + MAX31827_CONFIGURATION_REG, &uval); > + uval = FIELD_GET(MAX31827_CONFIGURATION_CNV_RATE_MASK, > + uval); > + switch (uval) { > + case MAX31827_CNV_1_DIV_64_HZ: > + *val = 64000; > + break; > + case MAX31827_CNV_1_DIV_32_HZ: > + *val = 32000; > + break; > + case MAX31827_CNV_1_DIV_16_HZ: > + *val = 16000; > + break; > + case MAX31827_CNV_1_DIV_4_HZ: > + *val = 4000; > + break; > + case MAX31827_CNV_1_HZ: > + *val = 1000; > + break; > + case MAX31827_CNV_4_HZ: > + *val = 250; > + break; > + case MAX31827_CNV_8_HZ: > + *val = 125; > + break; > + default: > + *val = 0; > + break; > + } > + } > + break; > + > + default: > + ret = -EOPNOTSUPP; > + break; > + } > + > + if (ret) > + return ret; > + > + return 0; just return ret; would do the same. > +} > + > +static int max31827_write(struct device *dev, enum hwmon_sensor_types type, > + u32 attr, int channel, long val) { > + struct max31827_state *st = dev_get_drvdata(dev); > + > + switch (type) { > + case hwmon_temp: > + switch (attr) { > + case hwmon_temp_enable: > + if (val >> 1) > + return -EOPNOTSUPP; > + > + st->enable = val; > + > + return regmap_update_bits(st->regmap, > + MAX31827_CONFIGURATION_REG, > + MAX31827_CONFIGURATION_1SHOT_MASK | > + MAX31827_CONFIGURATION_CNV_RATE_MASK, > + MAX31827_DEVICE_ENABLE(val)); > + > + case hwmon_temp_max: > + return write_alarm_val(st, MAX31827_TH_REG, val); > + > + case hwmon_temp_max_hyst: > + return write_alarm_val(st, MAX31827_TH_HYST_REG, val); > + > + case hwmon_temp_min: > + return write_alarm_val(st, MAX31827_TL_REG, val); > + > + case hwmon_temp_min_hyst: > + return write_alarm_val(st, MAX31827_TL_HYST_REG, val); > + > + default: > + return -EOPNOTSUPP; > + } > + > + case hwmon_chip: > + if (attr == hwmon_chip_update_interval) { > + switch (val) { > + case 125: > + val = MAX31827_CNV_8_HZ; > + break; > + case 250: > + val = MAX31827_CNV_4_HZ; > + break; > + case 1000: > + val = MAX31827_CNV_1_HZ; > + break; > + case 4000: > + val = MAX31827_CNV_1_DIV_4_HZ; > + break; > + case 16000: > + val = MAX31827_CNV_1_DIV_16_HZ; > + break; > + case 32000: > + val = MAX31827_CNV_1_DIV_32_HZ; > + break; > + case 64000: > + val = MAX31827_CNV_1_DIV_64_HZ; > + break; > + default: > + val = 0; > + break; > + } > + > + if (!val) > + return -EOPNOTSUPP; Might as well return from default: above. True, but I wrote it like this for consistency: in a switch statement I am either returning, either breaking. Should I still change it? > + > + val = FIELD_PREP(MAX31827_CONFIGURATION_CNV_RATE_MASK, > + val); > + > + return regmap_update_bits(st->regmap, > + MAX31827_CONFIGURATION_REG, > + MAX31827_CONFIGURATION_CNV_RATE_MASK, > + val); > + } > + break; > + > + default: > + return -EOPNOTSUPP; > + } > + > + return -EOPNOTSUPP; > +} > + > +static int max31827_init_client(struct max31827_state *st) { > + st->enable = true; > + > + return regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG, > + MAX31827_CONFIGURATION_1SHOT_MASK | > + MAX31827_CONFIGURATION_CNV_RATE_MASK, > + MAX31827_DEVICE_ENABLE(1)); > +} > + > +static const struct hwmon_channel_info *max31827_info[] = { > + HWMON_CHANNEL_INFO(temp, HWMON_T_ENABLE | HWMON_T_INPUT | HWMON_T_MIN | > + HWMON_T_MIN_HYST | HWMON_T_MIN_ALARM | > + HWMON_T_MAX | HWMON_T_MAX_HYST | > + HWMON_T_MAX_ALARM), > + HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL), > + NULL, > +}; > + > +static const struct hwmon_ops max31827_hwmon_ops = { > + .is_visible = max31827_is_visible, > + .read = max31827_read, > + .write = max31827_write, > +}; > + > +static const struct hwmon_chip_info max31827_chip_info = { > + .ops = &max31827_hwmon_ops, > + .info = max31827_info, > +}; > + > +static int max31827_probe(struct i2c_client *client) { > + struct device *dev = &client->dev; > + struct device *hwmon_dev; > + struct max31827_state *st; > + int err; > + > + if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA)) > + return -EOPNOTSUPP; > + > + st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL); > + if (!st) > + return -ENOMEM; > + > + mutex_init(&st->lock); > + > + st->regmap = devm_regmap_init_i2c(client, &max31827_regmap); > + if (IS_ERR(st->regmap)) > + return dev_err_probe(dev, PTR_ERR(st->regmap), > + "Failed to allocate regmap.\n"); > + > + err = max31827_init_client(st); > + if (err) > + return err; > + > + hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, st, > + &max31827_chip_info, > + NULL); > + > + return PTR_ERR_OR_ZERO(hwmon_dev); > +} > + > +static const struct i2c_device_id max31827_i2c_ids[] = { > + { "max31827", 0 }, > + { } > +}; > +MODULE_DEVICE_TABLE(i2c, max31827_i2c_ids); > + > +static const struct of_device_id max31827_of_match[] = { > + { .compatible = "max31827" }, > + { } > +}; > +MODULE_DEVICE_TABLE(of, max31827_of_match); > + > +static struct i2c_driver max31827_driver = { > + .class = I2C_CLASS_HWMON, > + .driver = { > + .name = "max31827", > + .of_match_table = max31827_of_match, > + }, > + .probe_new = max31827_probe, > + .id_table = max31827_i2c_ids, > +}; > +module_i2c_driver(max31827_driver); > + > +MODULE_AUTHOR("Daniel Matyas <daniel.matyas@xxxxxxxxxx>"); > +MODULE_DESCRIPTION("Maxim MAX31827 low-power temperature switch > +driver"); MODULE_LICENSE("GPL");
