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rtc: bq32000: add support to enable disable the trickle charge FET bypass
The bq32000 includes a trickle charge circuit to maintain the charge of the backup supply when a super capacitor is used. You can enable the charging circuit by setting 'trickle-resistor-ohms', additionally you can set TCFE to 1 to bypass the internal diode and boost the charge voltage of the backup supply. You might want to enable/disable the TCFE switch from userspace (e.g when device is only connected to a battery) This patch introduces a new sysfs entry to enable and disable this FET form userspace. Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
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Documentation/ABI/testing/sysfs-bus-i2c-devices-bq32k
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7
Documentation/ABI/testing/sysfs-bus-i2c-devices-bq32k
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@ -0,0 +1,7 @@
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What: /sys/bus/i2c/devices/.../trickle_charge_bypass
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Date: Jan 2017
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KernelVersion: 4.11
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Contact: Enric Balletbo i Serra <eballetbo@gmail.com>
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Description: Attribute for enable/disable the trickle charge bypass
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The trickle_charge_bypass attribute allows the userspace to
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enable/disable the Trickle charge FET bypass.
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@ -34,6 +34,7 @@
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#define BQ32K_CALIBRATION 0x07 /* CAL_CFG1, calibration and control */
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#define BQ32K_TCH2 0x08 /* Trickle charge enable */
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#define BQ32K_CFG2 0x09 /* Trickle charger control */
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#define BQ32K_TCFE BIT(6) /* Trickle charge FET bypass */
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struct bq32k_regs {
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uint8_t seconds;
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@ -188,6 +189,65 @@ static int trickle_charger_of_init(struct device *dev, struct device_node *node)
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return 0;
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}
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static ssize_t bq32k_sysfs_show_tricklecharge_bypass(struct device *dev,
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struct device_attribute *attr,
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char *buf)
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{
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int reg, error;
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error = bq32k_read(dev, ®, BQ32K_CFG2, 1);
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if (error)
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return error;
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return sprintf(buf, "%d\n", (reg & BQ32K_TCFE) ? 1 : 0);
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}
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static ssize_t bq32k_sysfs_store_tricklecharge_bypass(struct device *dev,
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struct device_attribute *attr,
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const char *buf, size_t count)
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{
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int reg, enable, error;
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if (kstrtoint(buf, 0, &enable))
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return -EINVAL;
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error = bq32k_read(dev, ®, BQ32K_CFG2, 1);
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if (error)
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return error;
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if (enable) {
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reg |= BQ32K_TCFE;
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error = bq32k_write(dev, ®, BQ32K_CFG2, 1);
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if (error)
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return error;
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dev_info(dev, "Enabled trickle charge FET bypass.\n");
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} else {
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reg &= ~BQ32K_TCFE;
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error = bq32k_write(dev, ®, BQ32K_CFG2, 1);
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if (error)
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return error;
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dev_info(dev, "Disabled trickle charge FET bypass.\n");
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}
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return count;
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}
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static DEVICE_ATTR(trickle_charge_bypass, 0644,
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bq32k_sysfs_show_tricklecharge_bypass,
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bq32k_sysfs_store_tricklecharge_bypass);
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static int bq32k_sysfs_register(struct device *dev)
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{
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return device_create_file(dev, &dev_attr_trickle_charge_bypass);
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}
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static void bq32k_sysfs_unregister(struct device *dev)
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{
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device_remove_file(dev, &dev_attr_trickle_charge_bypass);
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}
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static int bq32k_probe(struct i2c_client *client,
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const struct i2c_device_id *id)
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{
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@ -224,11 +284,26 @@ static int bq32k_probe(struct i2c_client *client,
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if (IS_ERR(rtc))
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return PTR_ERR(rtc);
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error = bq32k_sysfs_register(&client->dev);
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if (error) {
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dev_err(&client->dev,
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"Unable to create sysfs entries for rtc bq32000\n");
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return error;
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}
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i2c_set_clientdata(client, rtc);
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return 0;
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}
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static int bq32k_remove(struct i2c_client *client)
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{
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bq32k_sysfs_unregister(&client->dev);
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return 0;
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}
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static const struct i2c_device_id bq32k_id[] = {
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{ "bq32000", 0 },
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{ }
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@ -240,6 +315,7 @@ static struct i2c_driver bq32k_driver = {
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.name = "bq32k",
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},
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.probe = bq32k_probe,
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.remove = bq32k_remove,
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.id_table = bq32k_id,
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};
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