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Message-Id: <20230126-b4-ltc2945_shunt_resistor-v4-4-bb913470d8da@criticallink.com>
Date: Thu, 26 Jan 2023 17:32:26 -0500
From: Jonathan Cormier <jcormier@...ticallink.com>
To: Jean Delvare <jdelvare@...e.com>,
Guenter Roeck <linux@...ck-us.net>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc: linux-hwmon@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, Bob Duke <bduke@...ticallink.com>,
John Pruitt <jpruitt@...ticallink.com>,
Jonathan Cormier <jcormier@...ticallink.com>
Subject: [PATCH v4 4/5] hwmon: ltc2945: Allow setting shunt resistor
From: John Pruitt <jpruitt@...ticallink.com>
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 <jcormier@...ticallink.com>
Signed-off-by: John Pruitt <jpruitt@...ticallink.com>
---
drivers/hwmon/ltc2945.c | 117 +++++++++++++++++++++++++++++++-----------------
1 file changed, 75 insertions(+), 42 deletions(-)
diff --git a/drivers/hwmon/ltc2945.c b/drivers/hwmon/ltc2945.c
index ac15298a6558..0b5e448b4f12 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:
@@ -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);
}
--
2.25.1
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