[PATCH v3] Add LTC2941/LTC2943 Battery Gauge Driver

From: Mike Looijmans
Date: Wed Oct 08 2014 - 02:05:43 EST

Both the LTC2941 and LTC2943 measure battery capacity.
The LTC2943 is compatible with the LTC2941, it adds voltage and
temperature monitoring, and uses a slightly different conversion
formula for the charge counter.

To avoid confusion with e.g. the LTC2945, the driver is called
LTC2941 instead of LTC294X.

v2: Fix units of measurement: uV, uA and centidegrees.
v3: Correctly set configuration register. Allow negative values
for the sense resistor.

Signed-off-by: Mike Looijmans <mike.looijmans@xxxxxxxx>
---
drivers/power/Kconfig | 7 +
drivers/power/Makefile | 1 +
drivers/power/ltc2941-battery-gauge.c | 524 +++++++++++++++++++++++++++++++++
3 files changed, 532 insertions(+)
create mode 100644 drivers/power/ltc2941-battery-gauge.c

diff --git a/drivers/power/Kconfig b/drivers/power/Kconfig
index 73cfcdf..3333bf3 100644
--- a/drivers/power/Kconfig
+++ b/drivers/power/Kconfig
@@ -382,6 +382,13 @@ config CHARGER_TPS65090
Say Y here to enable support for battery charging with TPS65090
PMIC chips.

+config BATTERY_GAUGE_LTC2941
+ tristate "LTC2941/LTC2943 Battery Gauge Driver"
+ depends on I2C
+ help
+ Say Y here to include support for LTC2941 and LTC2943 Battery Gauge
+ IC.
+
config AB8500_BM
bool "AB8500 Battery Management Driver"
depends on AB8500_CORE && AB8500_GPADC
diff --git a/drivers/power/Makefile b/drivers/power/Makefile
index dfa8942..4f8e6c0 100644
--- a/drivers/power/Makefile
+++ b/drivers/power/Makefile
@@ -36,6 +36,7 @@ obj-$(CONFIG_BATTERY_MAX17042) += max17042_battery.o
obj-$(CONFIG_BATTERY_Z2) += z2_battery.o
obj-$(CONFIG_BATTERY_S3C_ADC) += s3c_adc_battery.o
obj-$(CONFIG_BATTERY_TWL4030_MADC) += twl4030_madc_battery.o
+obj-$(CONFIG_BATTERY_GAUGE_LTC2941) += ltc2941-battery-gauge.o
obj-$(CONFIG_CHARGER_88PM860X) += 88pm860x_charger.o
obj-$(CONFIG_CHARGER_PCF50633) += pcf50633-charger.o
obj-$(CONFIG_BATTERY_JZ4740) += jz4740-battery.o
diff --git a/drivers/power/ltc2941-battery-gauge.c b/drivers/power/ltc2941-battery-gauge.c
new file mode 100644
index 0000000..f0c387d
--- /dev/null
+++ b/drivers/power/ltc2941-battery-gauge.c
@@ -0,0 +1,524 @@
+/*
+ * I2C client/driver for the Linear Technology LTC2941 and LTC2943
+ * Battery Gas Gauge IC
+ *
+ * Copyright (C) 2014 Topic Embedded Systems
+ *
+ * Author: Auryn Verwegen
+ * Author: Mike Looijmans
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/swab.h>
+#include <linux/i2c.h>
+#include <linux/delay.h>
+#include <linux/idr.h>
+#include <linux/power_supply.h>
+#include <linux/slab.h>
+
+#define I16_MSB(x) ((x >> 8) & 0xFF)
+#define I16_LSB(x) (x & 0xFF)
+
+#define LTC294X_WORK_DELAY 10 /* Update delay in seconds */
+
+#define LTC294X_MAX_VALUE 0xFFFF
+#define LTC294X_MID_SUPPLY 0x7FFF
+
+#define LTC2941_MAX_PRESCALER_EXP 7
+#define LTC2943_MAX_PRESCALER_EXP 6
+
+enum ltc294x_reg {
+ LTC294X_REG_STATUS = 0x00,
+ LTC294X_REG_CONTROL = 0x01,
+ LTC294X_REG_ACC_CHARGE_MSB = 0x02,
+ LTC294X_REG_ACC_CHARGE_LSB = 0x03,
+ LTC294X_REG_THRESH_HIGH_MSB = 0x04,
+ LTC294X_REG_THRESH_HIGH_LSB = 0x05,
+ LTC294X_REG_THRESH_LOW_MSB = 0x06,
+ LTC294X_REG_THRESH_LOW_LSB = 0x07,
+ LTC294X_REG_VOLTAGE_MSB = 0x08,
+ LTC294X_REG_VOLTAGE_LSB = 0x09,
+ LTC294X_REG_CURRENT_MSB = 0x0E,
+ LTC294X_REG_CURRENT_LSB = 0x0F,
+ LTC294X_REG_TEMPERATURE_MSB = 0x14,
+ LTC294X_REG_TEMPERATURE_LSB = 0x15,
+} ;
+
+#define LTC2943_REG_CONTROL_MODE_MASK (BIT(7) | BIT(6))
+#define LTC2943_REG_CONTROL_MODE_SCAN BIT(7)
+#define LTC294X_REG_CONTROL_PRESCALER_MASK (BIT(5) | BIT(4) | BIT(3))
+#define LTC294X_REG_CONTROL_SHUTDOWN_MASK (BIT(0))
+#define LTC294X_REG_CONTROL_PRESCALER_SET(x) ((x << 3) & LTC294X_REG_CONTROL_PRESCALER_MASK)
+#define LTC294X_REG_CONTROL_ALCC_CONFIG_DISABLED 0
+
+#define LTC2941_NUM_REGS 0x08
+#define LTC2943_NUM_REGS 0x18
+
+struct ltc294x_info {
+ struct i2c_client *client; /* I2C Client pointer */
+ struct power_supply supply; /* Supply pointer */
+ struct delayed_work work; /* Work scheduler */
+ int num_regs; /* Number of registers (chip type) */
+ int id; /* Identifier of ltc294x chip */
+ int charge; /* Last charge register content */
+ int r_sense; /* mOhm */
+ int Qlsb; /* nAh */
+};
+
+static DEFINE_IDR(ltc294x_id);
+static DEFINE_MUTEX(ltc294x_lock);
+
+static inline int convert_bin_to_uAh(
+ const struct ltc294x_info *info, int Q)
+{
+ int uAh;
+ uAh = ((Q * (info->Qlsb / 10))) / 100;
+ return uAh;
+}
+
+static inline int convert_uAh_to_bin(
+ const struct ltc294x_info *info, int uAh)
+{
+ int Q;
+ Q = (uAh * 100) / (info->Qlsb/10);
+ return (Q < LTC294X_MAX_VALUE) ? Q : LTC294X_MAX_VALUE;
+}
+
+static int ltc294x_read_regs(struct i2c_client *client,
+ enum ltc294x_reg reg, u8 *buf, int num_regs)
+{
+ int ret;
+ struct i2c_msg msgs[2] = { };
+ u8 reg_start = reg;
+
+ msgs[0].addr = client->addr;
+ msgs[0].len = 1;
+ msgs[0].buf = &reg_start;
+
+ msgs[1].addr = client->addr;
+ msgs[1].len = num_regs;
+ msgs[1].buf = buf;
+ msgs[1].flags = I2C_M_RD;
+
+ ret = i2c_transfer(client->adapter, &msgs[0], 2);
+ if (ret < 0) {
+ dev_err(&client->dev, "ltc2941 read_reg failed!\n");
+ return ret;
+ }
+
+ dev_dbg(&client->dev, "%s (%#x, %d) -> %#x\n",
+ __func__, reg, num_regs, *buf);
+
+ return 0;
+}
+
+static int ltc294x_write_regs(struct i2c_client *client,
+ enum ltc294x_reg reg, const u8* const buf, int num_regs)
+{
+ int ret;
+ u8 reg_start = reg;
+
+ ret = i2c_smbus_write_i2c_block_data(client, reg_start, num_regs, buf);
+ if (ret < 0) {
+ dev_err(&client->dev, "ltc2941 write_reg failed!\n");
+ return ret;
+ }
+
+ dev_dbg(&client->dev, "%s (%#x, %d) -> %#x\n",
+ __func__, reg, num_regs, *buf);
+
+ return 0;
+}
+
+static int ltc294x_reset(const struct ltc294x_info *info, int prescaler_exp)
+{
+ int ret;
+ u8 value;
+ u8 control;
+
+ /* Read status and control registers */
+ ret = ltc294x_read_regs(info->client, LTC294X_REG_CONTROL, &value, 1);
+ if(ret < 0) {
+ dev_err(&info->client->dev, "LTC2941: Could not read registers from device!\n");
+ goto error_exit;
+ }
+
+ control = LTC294X_REG_CONTROL_PRESCALER_SET(prescaler_exp) |
+ LTC294X_REG_CONTROL_ALCC_CONFIG_DISABLED;
+ /* Put the 2943 into "monitor" mode, so it measures every 10 sec */
+ if (info->num_regs == LTC2943_NUM_REGS)
+ control |= LTC2943_REG_CONTROL_MODE_SCAN;
+
+ if (value != control) {
+ ret = ltc294x_write_regs(info->client, LTC294X_REG_CONTROL, &control, 1);
+ if(ret < 0){
+ dev_err(&info->client->dev, "Could not write registers!\n");
+ goto error_exit;
+ }
+ }
+
+ return 0;
+
+error_exit:
+ return ret;
+}
+
+static int ltc294x_read_charge_register(const struct ltc294x_info *info)
+{
+ int ret;
+ u8 datar[2];
+
+ ret = ltc294x_read_regs(info->client, LTC294X_REG_ACC_CHARGE_MSB, &datar[0], 2);
+ if (ret < 0)
+ return ret;
+ return (datar[0] << 8) + datar[1];
+}
+
+static int ltc294x_get_charge_now(const struct ltc294x_info *info, int *val)
+{
+ int value = ltc294x_read_charge_register(info);
+ if (value < 0)
+ return value;
+ /* When r_sense < 0, this counts up when the battery discharges */
+ if (info->Qlsb < 0)
+ value -= 0xFFFF;
+ *val = convert_bin_to_uAh(info, value);
+ return 0;
+}
+
+static int ltc294x_set_charge_now(const struct ltc294x_info *info, int val)
+{
+ int ret;
+ u8 dataw[2];
+ u8 ctrl_reg;
+ s32 value;
+
+ value = convert_uAh_to_bin(info, val);
+ if (info->Qlsb < 0) /* Direction depends on how sense+/- were connected */
+ value += 0xFFFF;
+ if ((value < 0) || (value > 0xFFFF)) /* input validation */
+ return -EINVAL;
+
+ /* Read control register */
+ ret = ltc294x_read_regs(info->client, LTC294X_REG_CONTROL, &ctrl_reg, 1);
+ if(ret < 0)
+ return ret;
+ /* Disable analog section */
+ ctrl_reg |= LTC294X_REG_CONTROL_SHUTDOWN_MASK;
+ ret = ltc294x_write_regs(info->client, LTC294X_REG_CONTROL, &ctrl_reg, 1);
+ if(ret < 0)
+ return ret;
+ /* Set new charge value */
+ dataw[0] = I16_MSB(value);
+ dataw[1] = I16_LSB(value);
+ ret = ltc294x_write_regs(info->client, LTC294X_REG_ACC_CHARGE_MSB, &dataw[0], 2);
+ if(ret < 0)
+ goto error_exit;
+ /* Enable analog section */
+error_exit:
+ ctrl_reg &= ~LTC294X_REG_CONTROL_SHUTDOWN_MASK;
+ ret = ltc294x_write_regs(info->client, LTC294X_REG_CONTROL, &ctrl_reg, 1);
+
+ return ret < 0 ? ret : 0;
+}
+
+static int ltc294x_get_charge_counter(const struct ltc294x_info *info, int *val)
+{
+ int value = ltc294x_read_charge_register(info);
+ if (value < 0)
+ return value;
+ value -= LTC294X_MID_SUPPLY;
+ *val = convert_bin_to_uAh(info, value);
+ return 0;
+}
+
+static int ltc294x_get_voltage(const struct ltc294x_info *info, int *val)
+{
+ int ret;
+ u8 datar[2];
+ u32 value;
+
+ ret = ltc294x_read_regs(info->client, LTC294X_REG_VOLTAGE_MSB, &datar[0], 2);
+ value = (datar[0] << 8) | datar[1];
+ *val = ((value * 23600) / 0xFFFF) * 1000; /* in uV */
+ return ret;
+}
+
+static int ltc294x_get_current(const struct ltc294x_info *info, int *val)
+{
+ int ret;
+ u8 datar[2];
+ s32 value;
+
+ ret = ltc294x_read_regs(info->client, LTC294X_REG_CURRENT_MSB, &datar[0], 2);
+ value = (datar[0] << 8) | datar[1];
+ value -= 0x7FFF;
+ /* Value is in range -32k..+32k, r_sense is usually 10..50 mOhm,
+ * the formula below keeps everything in s32 range while preserving
+ * enough digits */
+ *val = 1000 * ((60000 * value) / (info->r_sense * 0x7FFF)); /* in uA */
+ return ret;
+}
+
+static int ltc294x_get_temperature(const struct ltc294x_info *info, int *val)
+{
+ int ret;
+ u8 datar[2];
+ u32 value;
+
+ ret = ltc294x_read_regs(info->client, LTC294X_REG_TEMPERATURE_MSB, &datar[0], 2);
+ value = (datar[0] << 8) | datar[1];
+ /* Full-scale is 510 Kelvin, convert to centidegrees */
+ *val = (((51000 * value) / 0xFFFF) - 27215);
+ return ret;
+}
+
+static int ltc294x_get_property(struct power_supply *psy,
+ enum power_supply_property prop,
+ union power_supply_propval *val)
+{
+ struct ltc294x_info *info = container_of(psy, struct ltc294x_info, supply);
+
+ switch (prop) {
+ case POWER_SUPPLY_PROP_CHARGE_NOW:
+ return ltc294x_get_charge_now(info, &val->intval);
+ case POWER_SUPPLY_PROP_CHARGE_COUNTER:
+ return ltc294x_get_charge_counter(info, &val->intval);
+ case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+ return ltc294x_get_voltage(info, &val->intval);
+ case POWER_SUPPLY_PROP_CURRENT_NOW:
+ return ltc294x_get_current(info, &val->intval);
+ case POWER_SUPPLY_PROP_TEMP:
+ return ltc294x_get_temperature(info, &val->intval);
+ default:
+ return -EINVAL;
+ }
+}
+
+static int ltc294x_set_property(struct power_supply *psy,
+ enum power_supply_property psp,
+ const union power_supply_propval *val)
+{
+ struct ltc294x_info *info =
+ container_of(psy, struct ltc294x_info, supply);
+
+ switch (psp) {
+ case POWER_SUPPLY_PROP_CHARGE_NOW:
+ return ltc294x_set_charge_now(info, val->intval);
+ default:
+ return -EPERM;
+ }
+}
+
+static int ltc294x_property_is_writeable(
+ struct power_supply *psy, enum power_supply_property psp)
+{
+ switch (psp)
+ {
+ case POWER_SUPPLY_PROP_CHARGE_NOW:
+ return 1;
+ default:
+ return 0;
+ }
+}
+
+static void ltc294x_update(struct ltc294x_info *info)
+{
+ int charge = ltc294x_read_charge_register(info);
+ if (charge != info->charge) {
+ info->charge = charge;
+ power_supply_changed(&info->supply);
+ }
+}
+
+static void ltc294x_work(struct work_struct *work)
+{
+ struct ltc294x_info *info;
+
+ info = container_of(work, struct ltc294x_info, work.work);
+ ltc294x_update(info);
+ schedule_delayed_work(&info->work, LTC294X_WORK_DELAY * HZ);
+}
+
+static enum power_supply_property ltc294x_properties[] = {
+ POWER_SUPPLY_PROP_CHARGE_COUNTER,
+ POWER_SUPPLY_PROP_CHARGE_NOW,
+ POWER_SUPPLY_PROP_VOLTAGE_NOW,
+ POWER_SUPPLY_PROP_CURRENT_NOW,
+ POWER_SUPPLY_PROP_TEMP,
+};
+
+static int ltc294x_i2c_remove(struct i2c_client *client)
+{
+ struct ltc294x_info *info = i2c_get_clientdata(client);
+
+ cancel_delayed_work(&info->work);
+ power_supply_unregister(&info->supply);
+ kfree(info->supply.name);
+ mutex_lock(&ltc294x_lock);
+ idr_remove(&ltc294x_id, info->id);
+ mutex_unlock(&ltc294x_lock);
+ return 0;
+}
+
+static int ltc294x_i2c_probe(struct i2c_client *client, const struct i2c_device_id *id)
+{
+ struct ltc294x_info *info;
+ int ret;
+ int num;
+ u32 prescaler_exp;
+ s32 r_sense;
+ struct device_node *np;
+
+ mutex_lock(&ltc294x_lock);
+ ret = idr_alloc(&ltc294x_id, client, 0, 0, GFP_KERNEL);
+ mutex_unlock(&ltc294x_lock);
+ if(ret < 0)
+ goto fail_id;
+
+ num = ret;
+
+ info = devm_kzalloc(&client->dev, sizeof(*info), GFP_KERNEL);
+ if(info == NULL) {
+ dev_err(&client->dev, "Could not allocate memory for device structure!\n");
+ ret = -ENOMEM;
+ goto fail_info;
+ }
+
+ i2c_set_clientdata(client, info);
+
+ info->num_regs = id->driver_data;
+ info->supply.name = kasprintf(GFP_KERNEL, "%s-%d", client->name, num);
+ if(!info->supply.name) {
+ dev_err(&client->dev, "Could not allocate memory for device name!\n");
+ ret = -ENOMEM;
+ goto fail_name;
+ }
+
+ np = of_node_get(client->dev.of_node);
+
+ /* r_sense can be negative, when sense+ is connected to the battery
+ * instead of the sense-. This results in reversed measurements. */
+ ret = of_property_read_u32(np, "resistor-sense", &r_sense);
+ if(ret < 0) {
+ dev_err(&client->dev, "Could not find resistor-sense in devicetree!\n");
+ goto fail_name;
+ }
+ info->r_sense = r_sense;
+
+ ret = of_property_read_u32(np, "prescaler-exponent", &prescaler_exp);
+ if(ret < 0) {
+ dev_err(&client->dev, "PrescalerExponent not in devicetree, assume max.\n");
+ prescaler_exp = LTC2941_MAX_PRESCALER_EXP;
+ }
+
+ if (info->num_regs == LTC2943_NUM_REGS) {
+ if (prescaler_exp > LTC2943_MAX_PRESCALER_EXP)
+ prescaler_exp = LTC2943_MAX_PRESCALER_EXP;
+ info->Qlsb = ((340 * 50000) / r_sense) / (4096 / (1 << (2*prescaler_exp)));
+ } else {
+ if (prescaler_exp > LTC2941_MAX_PRESCALER_EXP)
+ prescaler_exp = LTC2941_MAX_PRESCALER_EXP;
+ info->Qlsb = ((58 * 50000) / r_sense) / (128 / (1 << prescaler_exp));
+ }
+
+ info->client = client;
+ info->id = num;
+ info->supply.type = POWER_SUPPLY_TYPE_BATTERY;
+ info->supply.properties = ltc294x_properties;
+ if (info->num_regs >= LTC294X_REG_TEMPERATURE_LSB)
+ info->supply.num_properties = ARRAY_SIZE(ltc294x_properties);
+ else if (info->num_regs >= LTC294X_REG_CURRENT_LSB)
+ info->supply.num_properties = ARRAY_SIZE(ltc294x_properties) - 1;
+ else if (info->num_regs >= LTC294X_REG_VOLTAGE_LSB)
+ info->supply.num_properties = ARRAY_SIZE(ltc294x_properties) - 2;
+ else
+ info->supply.num_properties = ARRAY_SIZE(ltc294x_properties) - 3;
+ info->supply.get_property = ltc294x_get_property;
+ info->supply.set_property = ltc294x_set_property;
+ info->supply.property_is_writeable = ltc294x_property_is_writeable;
+ info->supply.external_power_changed = NULL;
+
+ INIT_DELAYED_WORK(&info->work, ltc294x_work);
+
+ ret = ltc294x_reset(info, prescaler_exp);
+ if (ret < 0) {
+ dev_err(&client->dev, "Communication with chip failed!\n");
+ goto fail_comm;
+ }
+
+ ret = power_supply_register(&client->dev, &info->supply);
+ if (ret) {
+ dev_err(&client->dev, "failed to register ltc2941\n");
+ goto fail_register;
+ } else {
+ schedule_delayed_work(&info->work, LTC294X_WORK_DELAY * HZ);
+ }
+
+ return 0;
+
+fail_register:
+ kfree(info->supply.name);
+fail_comm:
+fail_name:
+fail_info:
+ mutex_lock(&ltc294x_lock);
+ idr_remove(&ltc294x_id, num);
+ mutex_unlock(&ltc294x_lock);
+fail_id:
+ return ret;
+}
+
+#ifdef CONFIG_PM_SLEEP
+
+static int ltc294x_suspend(struct device *dev)
+{
+ struct i2c_client *client = to_i2c_client(dev);
+ struct ltc294x_info *info = i2c_get_clientdata(client);
+
+ cancel_delayed_work(&info->work);
+ return 0;
+}
+
+static int ltc294x_resume(struct device *dev)
+{
+ struct i2c_client *client = to_i2c_client(dev);
+ struct ltc294x_info *info = i2c_get_clientdata(client);
+
+ schedule_delayed_work(&info->work, LTC294X_WORK_DELAY * HZ);
+ return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(ltc294x_pm_ops, ltc294x_suspend, ltc294x_resume);
+#define LTC294X_PM_OPS (&ltc294x_pm_ops)
+
+#else
+#define LTC294X_PM_OPS NULL
+#endif /* CONFIG_PM_SLEEP */
+
+
+static const struct i2c_device_id ltc294x_i2c_id[] = {
+ {"ltc2941", LTC2941_NUM_REGS},
+ {"ltc2943", LTC2943_NUM_REGS},
+ { },
+};
+MODULE_DEVICE_TABLE(i2c, ltc294x_i2c_id);
+
+static struct i2c_driver ltc294x_driver = {
+ .driver = {
+ .name = "LTC2941",
+ .owner = THIS_MODULE,
+ .pm = LTC294X_PM_OPS,
+ },
+ .probe = ltc294x_i2c_probe,
+ .remove = ltc294x_i2c_remove,
+ .id_table = ltc294x_i2c_id,
+};
+module_i2c_driver(ltc294x_driver);
+
+MODULE_AUTHOR("Auryn Verwegen, Topic Embedded Systems");
+MODULE_AUTHOR("Mike Looijmans, Topic Embedded Products");
+MODULE_DESCRIPTION("LTC2941/LTC2943 Battery Gas Gauge IC driver");
+MODULE_LICENSE("GPL");
--
1.7.9.5

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