From b11f3d47c0e74e6c0515e31788651713a3a94a50 Mon Sep 17 00:00:00 2001 From: John Pruitt Date: Thu, 26 Jan 2023 17:32:26 -0500 Subject: [PATCH] hwmon: (ltc2945) Allow setting shunt resistor Add the ability to specify the value of the shunt resistor in the device tree instead of assuming it is 1 milliOhm. The value in the device tree has the name shunt-resistor-micro-ohms and the default value is 1000 micro-ohms in order to preserve the current behavior. Signed-off-by: Jonathan Cormier Signed-off-by: John Pruitt [groeck: Fixed multi-line alignment, squashed last patch of series] Signed-off-by: Guenter Roeck --- drivers/hwmon/ltc2945.c | 119 +++++++++++++++++++++++++--------------- 1 file changed, 76 insertions(+), 43 deletions(-) diff --git a/drivers/hwmon/ltc2945.c b/drivers/hwmon/ltc2945.c index ac15298a6558..3494f7261ebf 100644 --- a/drivers/hwmon/ltc2945.c +++ b/drivers/hwmon/ltc2945.c @@ -64,6 +64,16 @@ static const struct of_device_id __maybe_unused ltc2945_of_match[] = { }; MODULE_DEVICE_TABLE(of, ltc2945_of_match); +/** + * struct ltc2945_data - LTC2945 device data + * @regmap: regmap device + * @shunt_resistor: shunt resistor value in micro ohms (1000 by default) + */ +struct ltc2945_data { + struct regmap *regmap; + u32 shunt_resistor; +}; + static inline bool is_power_reg(u8 reg) { return reg < LTC2945_SENSE_H; @@ -72,7 +82,9 @@ static inline bool is_power_reg(u8 reg) /* Return the value from the given register in uW, mV, or mA */ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) { - struct regmap *regmap = dev_get_drvdata(dev); + struct ltc2945_data *data = dev_get_drvdata(dev); + struct regmap *regmap = data->regmap; + u32 shunt_resistor = data->shunt_resistor; unsigned int control; u8 buf[3]; long long val; @@ -84,10 +96,10 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) return ret; if (is_power_reg(reg)) { - /* power */ + /* 24-bit power */ val = (buf[0] << 16) + (buf[1] << 8) + buf[2]; } else { - /* current, voltage */ + /* 12-bit current, voltage */ val = (buf[0] << 4) + (buf[1] >> 4); } @@ -98,9 +110,7 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) case LTC2945_MAX_POWER_THRES_H: case LTC2945_MIN_POWER_THRES_H: /* - * Convert to uW by assuming current is measured with - * an 1mOhm sense resistor, similar to current - * measurements. + * Convert to uW * Control register bit 0 selects if voltage at SENSE+/VDD * or voltage at ADIN is used to measure power. */ @@ -114,6 +124,14 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) /* 0.5 mV * 25 uV = 0.0125 uV resolution. */ val = (val * 25LL) >> 1; } + val *= 1000; + /* Overflow check: Assuming max 24-bit power, val is at most 53 bits right now. */ + val = DIV_ROUND_CLOSEST_ULL(val, shunt_resistor); + /* + * Overflow check: After division, depending on shunt resistor, + * val can still be > 32 bits so returning long long makes sense + */ + break; case LTC2945_VIN_H: case LTC2945_MAX_VIN_H: @@ -136,14 +154,11 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) case LTC2945_MIN_SENSE_H: case LTC2945_MAX_SENSE_THRES_H: case LTC2945_MIN_SENSE_THRES_H: - /* - * 25 uV resolution. Convert to current as measured with - * an 1 mOhm sense resistor, in mA. If a different sense - * resistor is installed, calculate the actual current by - * dividing the reported current by the sense resistor value - * in mOhm. - */ - val *= 25; + /* 25 uV resolution. Convert to mA. */ + val *= 25 * 1000; + /* Overflow check: Assuming max 12-bit sense, val is at most 27 bits right now */ + val = DIV_ROUND_CLOSEST_ULL(val, shunt_resistor); + /* Overflow check: After division, <= 27 bits */ break; default: return -EINVAL; @@ -151,13 +166,18 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg) return val; } -static int ltc2945_val_to_reg(struct device *dev, u8 reg, - unsigned long val) +static long long ltc2945_val_to_reg(struct device *dev, u8 reg, + unsigned long long val) { - struct regmap *regmap = dev_get_drvdata(dev); + struct ltc2945_data *data = dev_get_drvdata(dev); + struct regmap *regmap = data->regmap; + u32 shunt_resistor = data->shunt_resistor; unsigned int control; int ret; + /* Ensure we don't overflow */ + val = clamp_val(val, 0, U32_MAX); + switch (reg) { case LTC2945_POWER_H: case LTC2945_MAX_POWER_H: @@ -165,9 +185,6 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, case LTC2945_MAX_POWER_THRES_H: case LTC2945_MIN_POWER_THRES_H: /* - * Convert to register value by assuming current is measured - * with an 1mOhm sense resistor, similar to current - * measurements. * Control register bit 0 selects if voltage at SENSE+/VDD * or voltage at ADIN is used to measure power, which in turn * determines register calculations. @@ -177,14 +194,16 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, return ret; if (control & CONTROL_MULT_SELECT) { /* 25 mV * 25 uV = 0.625 uV resolution. */ - val = DIV_ROUND_CLOSEST(val, 625); + val *= shunt_resistor; + /* Overflow check: Assuming 32-bit val and shunt resistor, val <= 64bits */ + val = DIV_ROUND_CLOSEST_ULL(val, 625 * 1000); + /* Overflow check: val is now <= 44 bits */ } else { - /* - * 0.5 mV * 25 uV = 0.0125 uV resolution. - * Divide first to avoid overflow; - * accept loss of accuracy. - */ - val = DIV_ROUND_CLOSEST(val, 25) * 2; + /* 0.5 mV * 25 uV = 0.0125 uV resolution. */ + val *= shunt_resistor; + /* Overflow check: Assuming 32-bit val and shunt resistor, val <= 64bits */ + val = DIV_ROUND_CLOSEST_ULL(val, 25 * 1000) * 2; + /* Overflow check: val is now <= 51 bits */ } break; case LTC2945_VIN_H: @@ -193,7 +212,7 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, case LTC2945_MAX_VIN_THRES_H: case LTC2945_MIN_VIN_THRES_H: /* 25 mV resolution. */ - val /= 25; + val = DIV_ROUND_CLOSEST_ULL(val, 25); break; case LTC2945_ADIN_H: case LTC2945_MAX_ADIN_H: @@ -208,14 +227,11 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg, case LTC2945_MIN_SENSE_H: case LTC2945_MAX_SENSE_THRES_H: case LTC2945_MIN_SENSE_THRES_H: - /* - * 25 uV resolution. Convert to current as measured with - * an 1 mOhm sense resistor, in mA. If a different sense - * resistor is installed, calculate the actual current by - * dividing the reported current by the sense resistor value - * in mOhm. - */ - val = DIV_ROUND_CLOSEST(val, 25); + /* 25 uV resolution. Convert to mA. */ + val *= shunt_resistor; + /* Overflow check: Assuming 32-bit val and 32-bit shunt resistor, val is 64bits */ + val = DIV_ROUND_CLOSEST_ULL(val, 25 * 1000); + /* Overflow check: val is now <= 50 bits */ break; default: return -EINVAL; @@ -240,15 +256,16 @@ static ssize_t ltc2945_value_store(struct device *dev, const char *buf, size_t count) { struct sensor_device_attribute *attr = to_sensor_dev_attr(da); - struct regmap *regmap = dev_get_drvdata(dev); + struct ltc2945_data *data = dev_get_drvdata(dev); + struct regmap *regmap = data->regmap; u8 reg = attr->index; - unsigned long val; + unsigned int val; u8 regbuf[3]; int num_regs; - int regval; + long long regval; int ret; - ret = kstrtoul(buf, 10, &val); + ret = kstrtouint(buf, 10, &val); if (ret) return ret; @@ -277,7 +294,8 @@ static ssize_t ltc2945_history_store(struct device *dev, const char *buf, size_t count) { struct sensor_device_attribute *attr = to_sensor_dev_attr(da); - struct regmap *regmap = dev_get_drvdata(dev); + struct ltc2945_data *data = dev_get_drvdata(dev); + struct regmap *regmap = data->regmap; u8 reg = attr->index; int num_regs = is_power_reg(reg) ? 3 : 2; u8 buf_min[3] = { 0xff, 0xff, 0xff }; @@ -329,7 +347,8 @@ static ssize_t ltc2945_bool_show(struct device *dev, struct device_attribute *da, char *buf) { struct sensor_device_attribute *attr = to_sensor_dev_attr(da); - struct regmap *regmap = dev_get_drvdata(dev); + struct ltc2945_data *data = dev_get_drvdata(dev); + struct regmap *regmap = data->regmap; unsigned int fault; int ret; @@ -458,6 +477,12 @@ static int ltc2945_probe(struct i2c_client *client) struct device *dev = &client->dev; struct device *hwmon_dev; struct regmap *regmap; + struct ltc2945_data *data; + + data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL); + if (!data) + return -ENOMEM; + dev_set_drvdata(dev, data); regmap = devm_regmap_init_i2c(client, <c2945_regmap_config); if (IS_ERR(regmap)) { @@ -465,11 +490,19 @@ static int ltc2945_probe(struct i2c_client *client) return PTR_ERR(regmap); } + data->regmap = regmap; + if (device_property_read_u32(dev, "shunt-resistor-micro-ohms", + &data->shunt_resistor)) + data->shunt_resistor = 1000; + + if (data->shunt_resistor == 0) + return -EINVAL; + /* Clear faults */ regmap_write(regmap, LTC2945_FAULT, 0x00); hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name, - regmap, + data, ltc2945_groups); return PTR_ERR_OR_ZERO(hwmon_dev); }