rtc: ds1307: add trickle charger support

Some DS13XX devices have "trickle chargers".  Its configuration register
is at different locations, the setup is the same, though.  Since the
configuration is board specific, introduce a platform_data to this driver.
Tested with a DS1339 on a custom board.
Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>
Cc: Alessandro Zummo <alessandro.zummo@towertech.it>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-ds1307.c

@@ -17,8 +17,7 @@
 #include <linux/string.h>
 #include <linux/rtc.h>
 #include <linux/bcd.h>
-
-
+#include <linux/rtc/ds1307.h>
 
 /*
  * We can't determine type by probing, but if we expect pre-Linux code
@@ -92,7 +91,8 @@ enum ds_type {
 #	define DS1337_BIT_A2I		0x02
 #	define DS1337_BIT_A1I		0x01
 #define DS1339_REG_ALARM1_SECS	0x07
-#define DS1339_REG_TRICKLE	0x10
+
+#define DS13XX_TRICKLE_CHARGER_MAGIC	0xa0
 
 #define RX8025_REG_CTRL1	0x0e
 #	define RX8025_BIT_2412		0x20
@@ -124,6 +124,7 @@ struct chip_desc {
 	unsigned		alarm:1;
 	u16			nvram_offset;
 	u16			nvram_size;
+	u16			trickle_charger_reg;
 };
 
 static const struct chip_desc chips[last_ds_type] = {
@@ -140,6 +141,13 @@ static const struct chip_desc chips[last_ds_type] = {
 	},
 	[ds_1339] = {
 		.alarm		= 1,
+		.trickle_charger_reg = 0x10,
+	},
+	[ds_1340] = {
+		.trickle_charger_reg = 0x08,
+	},
+	[ds_1388] = {
+		.trickle_charger_reg = 0x0a,
 	},
 	[ds_3231] = {
 		.alarm		= 1,
@@ -619,6 +627,7 @@ static int __devinit ds1307_probe(struct i2c_client *client,
 	struct i2c_adapter	*adapter = to_i2c_adapter(client->dev.parent);
 	int			want_irq = false;
 	unsigned char		*buf;
+	struct ds1307_platform_data *pdata = client->dev.platform_data;
 	static const int	bbsqi_bitpos[] = {
 		[ds_1337] = 0,
 		[ds_1339] = DS1339_BIT_BBSQI,
@@ -638,6 +647,10 @@ static int __devinit ds1307_probe(struct i2c_client *client,
 	ds1307->client	= client;
 	ds1307->type	= id->driver_data;
 
+	if (pdata && pdata->trickle_charger_setup && chip->trickle_charger_reg)
+		i2c_smbus_write_byte_data(client, chip->trickle_charger_reg,
+			DS13XX_TRICKLE_CHARGER_MAGIC | pdata->trickle_charger_setup);
+
 	buf = ds1307->regs;
 	if (i2c_check_functionality(adapter, I2C_FUNC_SMBUS_I2C_BLOCK)) {
 		ds1307->read_block_data = i2c_smbus_read_i2c_block_data;

include/linux/rtc/ds1307.h

+/*
+ * ds1307.h - platform_data for the ds1307 (and variants) rtc driver
+ * (C) Copyright 2012 by Wolfram Sang, Pengutronix e.K.
+ * same license as the driver
+ */
+
+#ifndef _LINUX_DS1307_H
+#define _LINUX_DS1307_H
+
+#include <linux/types.h>
+
+#define DS1307_TRICKLE_CHARGER_250_OHM	0x01
+#define DS1307_TRICKLE_CHARGER_2K_OHM	0x02
+#define DS1307_TRICKLE_CHARGER_4K_OHM	0x03
+#define DS1307_TRICKLE_CHARGER_NO_DIODE	0x04
+#define DS1307_TRICKLE_CHARGER_DIODE	0x08
+
+struct ds1307_platform_data {
+	u8 trickle_charger_setup;
+};
+
+#endif /* _LINUX_DS1307_H */