rtc: rtc-m41t80.c: add support for the ST M41T65 RTC

Add support for M41T65 Real Time Clock chip.

The main differences I see between the M41T65 and M41T80 are that:

1) The M41T65 watchdog timer has three bits controlling resolution
   (versus two for the M41T80).

2) There is no register 0x13 for controlling square-wave output.

Signed-off-by: Steven A. Falco <sfalco@harris.com>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>
Acked-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 33 insertions, 10 deletions

diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c
index 24bc1689fc74..470fb2d29545 100644
--- a/drivers/rtc/rtc-m41t80.c
+++ b/drivers/rtc/rtc-m41t80.c
@@ -56,21 +56,27 @@
 #define M41T80_ALHOUR_HT        (1 << 6)        /* HT: Halt Update Bit */
 #define M41T80_FLAGS_AF         (1 << 6)        /* AF: Alarm Flag Bit */
 #define M41T80_FLAGS_BATT_LOW   (1 << 4)        /* BL: Battery Low Bit */
+#define M41T80_WATCHDOG_RB2     (1 << 7)        /* RB: Watchdog resolution */
+#define M41T80_WATCHDOG_RB1     (1 << 1)        /* RB: Watchdog resolution */
+#define M41T80_WATCHDOG_RB0     (1 << 0)        /* RB: Watchdog resolution */
 
-#define M41T80_FEATURE_HT       (1 << 0)
-#define M41T80_FEATURE_BL       (1 << 1)
+#define M41T80_FEATURE_HT       (1 << 0)        /* Halt feature */
+#define M41T80_FEATURE_BL       (1 << 1)        /* Battery low indicator */
+#define M41T80_FEATURE_SQ       (1 << 2)        /* Squarewave feature */
+#define M41T80_FEATURE_WD       (1 << 3)        /* Extra watchdog resolution */
 
 #define DRV_VERSION "0.05"
 
 static const struct i2c_device_id m41t80_id[] = {
-        { "m41t80", 0 },
-        { "m41t81", M41T80_FEATURE_HT },
-        { "m41t81s", M41T80_FEATURE_HT | M41T80_FEATURE_BL },
-        { "m41t82", M41T80_FEATURE_HT | M41T80_FEATURE_BL },
-        { "m41t83", M41T80_FEATURE_HT | M41T80_FEATURE_BL },
-        { "m41st84", M41T80_FEATURE_HT | M41T80_FEATURE_BL },
-        { "m41st85", M41T80_FEATURE_HT | M41T80_FEATURE_BL },
-        { "m41st87", M41T80_FEATURE_HT | M41T80_FEATURE_BL },
+        { "m41t65", M41T80_FEATURE_HT | M41T80_FEATURE_WD },
+        { "m41t80", M41T80_FEATURE_SQ },
+        { "m41t81", M41T80_FEATURE_HT | M41T80_FEATURE_SQ},
+        { "m41t81s", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
+        { "m41t82", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
+        { "m41t83", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
+        { "m41st84", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
+        { "m41st85", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
+        { "m41st87", M41T80_FEATURE_HT | M41T80_FEATURE_BL | M41T80_FEATURE_SQ },
         { }
 };
 MODULE_DEVICE_TABLE(i2c, m41t80_id);
@@ -386,8 +392,12 @@ static ssize_t m41t80_sysfs_show_sqwfreq(struct device *dev,
                                 struct device_attribute *attr, char *buf)
 {
         struct i2c_client *client = to_i2c_client(dev);
+        struct m41t80_data *clientdata = i2c_get_clientdata(client);
         int val;
 
+        if (!(clientdata->features & M41T80_FEATURE_SQ))
+                return -EINVAL;
+
         val = i2c_smbus_read_byte_data(client, M41T80_REG_SQW);
         if (val < 0)
                 return -EIO;
@@ -408,9 +418,13 @@ static ssize_t m41t80_sysfs_set_sqwfreq(struct device *dev,
                                 const char *buf, size_t count)
 {
         struct i2c_client *client = to_i2c_client(dev);
+        struct m41t80_data *clientdata = i2c_get_clientdata(client);
         int almon, sqw;
         int val = simple_strtoul(buf, NULL, 0);
 
+        if (!(clientdata->features & M41T80_FEATURE_SQ))
+                return -EINVAL;
+
         if (val) {
                 if (!is_power_of_2(val))
                         return -EINVAL;
@@ -499,6 +513,8 @@ static void wdt_ping(void)
                         .buf    = i2c_data,
                 },
         };
+        struct m41t80_data *clientdata = i2c_get_clientdata(save_client);
+
         i2c_data[0] = 0x09;             /* watchdog register */
 
         if (wdt_margin > 31)
@@ -509,6 +525,13 @@ static void wdt_ping(void)
                  */
                 i2c_data[1] = wdt_margin<<2 | 0x82;
 
+        /*
+         * M41T65 has three bits for watchdog resolution.  Don't set bit 7, as
+         * that would be an invalid resolution.
+         */
+        if (clientdata->features & M41T80_FEATURE_WD)
+                i2c_data[1] &= ~M41T80_WATCHDOG_RB2;
+
         i2c_transfer(save_client->adapter, msgs1, 1);
 }