rtc: bq32000: add trickle charger option, with device tree binding

BQ32000 devices have "trickle chargers".  Introduce a code to enable the
charger, based on device tree.

Without charger, RTC does not keep time after power off.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Pavel Machek <pavel@denx.de>
Cc: Jason Cooper <jason@lakedameon.net>
Cc: Matti Vaittinen <matti.vaittinen@nsn.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 62 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-bq32k.c b/drivers/rtc/rtc-bq32k.c
index c74bf0dc52cc..314129e66d6e 100644
--- a/drivers/rtc/rtc-bq32k.c
+++ b/drivers/rtc/rtc-bq32k.c
@@ -2,10 +2,14 @@
  * Driver for TI BQ32000 RTC.
  *
  * Copyright (C) 2009 Semihalf.
+ * Copyright (C) 2014 Pavel Machek <pavel@denx.de>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
+ *
+ * You can get hardware description at
+ * http://www.ti.com/lit/ds/symlink/bq32000.pdf
  */
 
 #include <linux/module.h>
@@ -27,6 +31,10 @@
 #define BQ32K_CENT              0x40    /* Century flag */
 #define BQ32K_CENT_EN           0x80    /* Century flag enable bit */
 
+#define BQ32K_CALIBRATION       0x07    /* CAL_CFG1, calibration and control */
+#define BQ32K_TCH2              0x08    /* Trickle charge enable */
+#define BQ32K_CFG2              0x09    /* Trickle charger control */
+
 struct bq32k_regs {
         uint8_t         seconds;
         uint8_t         minutes;
@@ -122,6 +130,57 @@ static const struct rtc_class_ops bq32k_rtc_ops = {
         .set_time       = bq32k_rtc_set_time,
 };
 
+static int trickle_charger_of_init(struct device *dev, struct device_node *node)
+{
+        unsigned char reg;
+        int error;
+        u32 ohms = 0;
+
+        if (of_property_read_u32(node, "trickle-resistor-ohms" , &ohms))
+                return 0;
+
+        switch (ohms) {
+        case 180+940:
+                /*
+                 * TCHE[3:0] == 0x05, TCH2 == 1, TCFE == 0 (charging
+                 * over diode and 940ohm resistor)
+                 */
+
+                if (of_property_read_bool(node, "trickle-diode-disable")) {
+                        dev_err(dev, "diode and resistor mismatch\n");
+                        return -EINVAL;
+                }
+                reg = 0x05;
+                break;
+
+        case 180+20000:
+                /* diode disabled */
+
+                if (!of_property_read_bool(node, "trickle-diode-disable")) {
+                        dev_err(dev, "bq32k: diode and resistor mismatch\n");
+                        return -EINVAL;
+                }
+                reg = 0x25;
+                break;
+
+        default:
+                dev_err(dev, "invalid resistor value (%d)\n", ohms);
+                return -EINVAL;
+        }
+
+        error = bq32k_write(dev, &reg, BQ32K_CFG2, 1);
+        if (error)
+                return error;
+
+        reg = 0x20;
+        error = bq32k_write(dev, &reg, BQ32K_TCH2, 1);
+        if (error)
+                return error;
+
+        dev_info(dev, "Enabled trickle RTC battery charge.\n");
+        return 0;
+}
+
 static int bq32k_probe(struct i2c_client *client,
                                 const struct i2c_device_id *id)
 {
@@ -153,6 +212,9 @@ static int bq32k_probe(struct i2c_client *client,
         if (error)
                 return error;
 
+        if (client && client->dev.of_node)
+                trickle_charger_of_init(dev, client->dev.of_node);
+
         rtc = devm_rtc_device_register(&client->dev, bq32k_driver.driver.name,
                                                 &bq32k_rtc_ops, THIS_MODULE);
         if (IS_ERR(rtc))