w1: ds2760_battery: add support for sleep mode feature

This adds support for ds2760's sleep mode feature. With this feature
enabled, the chip enters a deep sleep mode and disconnects from the
battery when the w1 line is held down for more than 2 seconds.

This new behaviour can be switched on and off using a new module
parameter.

Signed-off-by: Daniel Mack <[e-mail]>
Cc: Szabolcs Gyurko <[e-mail]>
Acked-by: Matt Reimer <[e-mail]>
Acked-by: Evgeniy Polyakov <[e-mail]>
Signed-off-by: Anton Vorontsov <[e-mail]>

drivers/power/ds2760_battery.c

···
 module_param(cache_time, uint, 0644);
 MODULE_PARM_DESC(cache_time, "cache time in milliseconds");
 
+static unsigned int pmod_enabled;
+module_param(pmod_enabled, bool, 0644);
+MODULE_PARM_DESC(pmod_enabled, "PMOD enable bit");
+
 /* Some batteries have their rated capacity stored a N * 10 mAh, while
  * others use an index into this table. */
 static int rated_capacities[] = {
···
 		power_supply_changed(&di->bat);
 }
 
+static void ds2760_battery_write_status(struct ds2760_device_info *di,
+					char status)
+{
+	if (status == di->raw[DS2760_STATUS_REG])
+		return;
+
+	w1_ds2760_write(di->w1_dev, &status, DS2760_STATUS_WRITE_REG, 1);
+	w1_ds2760_store_eeprom(di->w1_dev, DS2760_EEPROM_BLOCK1);
+	w1_ds2760_recall_eeprom(di->w1_dev, DS2760_EEPROM_BLOCK1);
+}
+
 static void ds2760_battery_work(struct work_struct *work)
 {
 	struct ds2760_device_info *di = container_of(work,
···
 
 static int ds2760_battery_probe(struct platform_device *pdev)
 {
+	char status;
 	int retval = 0;
 	struct ds2760_device_info *di;
 
···
 		dev_err(di->dev, "failed to register battery\n");
 		goto batt_failed;
 	}
+
+	/* enable sleep mode feature */
+	ds2760_battery_read_status(di);
+	status = di->raw[DS2760_STATUS_REG];
+	if (pmod_enabled)
+		status |= DS2760_STATUS_PMOD;
+	else
+		status &= ~DS2760_STATUS_PMOD;
+
+	ds2760_battery_write_status(di, status);
 
 	INIT_DELAYED_WORK(&di->monitor_work, ds2760_battery_work);
 	di->monitor_wqueue = create_singlethread_workqueue(dev_name(&pdev->dev));

drivers/w1/slaves/w1_ds2760.h

···
 
 #define DS2760_PROTECTION_REG		0x00
 #define DS2760_STATUS_REG		0x01
+	#define DS2760_STATUS_IE	(1 << 2)
+	#define DS2760_STATUS_SWEN	(1 << 3)
+	#define DS2760_STATUS_RNAOP	(1 << 4)
+	#define DS2760_STATUS_PMOD	(1 << 5)
 #define DS2760_EEPROM_REG		0x07
 #define DS2760_SPECIAL_FEATURE_REG	0x08
 #define DS2760_VOLTAGE_MSB		0x0c
···
 #define DS2760_EEPROM_BLOCK0		0x20
 #define DS2760_ACTIVE_FULL		0x20
 #define DS2760_EEPROM_BLOCK1		0x30
+#define DS2760_STATUS_WRITE_REG		0x31
 #define DS2760_RATED_CAPACITY		0x32
 #define DS2760_CURRENT_OFFSET_BIAS	0x33
 #define DS2760_ACTIVE_EMPTY		0x3b