1 files changed, 34 insertions, 6 deletions

diff --git a/drivers/rtc/rtc-pcf8563.c b/drivers/rtc/rtc-pcf8563.c
index 4b72b8ef5d66..038118bbfaea 100644
--- a/drivers/rtc/rtc-pcf8563.c
+++ b/drivers/rtc/rtc-pcf8563.c
@@ -53,6 +53,25 @@ I2C_CLIENT_INSMOD;
 #define PCF8563_SC_LV           0x80 /* low voltage */
 #define PCF8563_MO_C            0x80 /* century */
 
+struct pcf8563 {
+        struct i2c_client client;
+        /*
+         * The meaning of MO_C bit varies by the chip type.
+         * From PCF8563 datasheet: this bit is toggled when the years
+         * register overflows from 99 to 00
+         *   0 indicates the century is 20xx
+         *   1 indicates the century is 19xx
+         * From RTC8564 datasheet: this bit indicates change of
+         * century. When the year digit data overflows from 99 to 00,
+         * this bit is set. By presetting it to 0 while still in the
+         * 20th century, it will be set in year 2000, ...
+         * There seems no reliable way to know how the system use this
+         * bit.  So let's do it heuristically, assuming we are live in
+         * 1970...2069.
+         */
+        int c_polarity; /* 0: MO_C=1 means 19xx, otherwise MO_C=1 means 20xx */
+};
+
 static int pcf8563_probe(struct i2c_adapter *adapter, int address, int kind);
 static int pcf8563_detach(struct i2c_client *client);
 
@@ -62,6 +81,7 @@ static int pcf8563_detach(struct i2c_client *client);
  */
 static int pcf8563_get_datetime(struct i2c_client *client, struct rtc_time *tm)
 {
+        struct pcf8563 *pcf8563 = container_of(client, struct pcf8563, client);
         unsigned char buf[13] = { PCF8563_REG_ST1 };
 
         struct i2c_msg msgs[] = {
@@ -94,8 +114,12 @@ static int pcf8563_get_datetime(struct i2c_client *client, struct rtc_time *tm)
         tm->tm_mday = BCD2BIN(buf[PCF8563_REG_DM] & 0x3F);
         tm->tm_wday = buf[PCF8563_REG_DW] & 0x07;
         tm->tm_mon = BCD2BIN(buf[PCF8563_REG_MO] & 0x1F) - 1; /* rtc mn 1-12 */
-        tm->tm_year = BCD2BIN(buf[PCF8563_REG_YR])
-                + (buf[PCF8563_REG_MO] & PCF8563_MO_C ? 0 : 100);
+        tm->tm_year = BCD2BIN(buf[PCF8563_REG_YR]);
+        if (tm->tm_year < 70)
+                tm->tm_year += 100;     /* assume we are in 1970...2069 */
+        /* detect the polarity heuristically. see note above. */
+        pcf8563->c_polarity = (buf[PCF8563_REG_MO] & PCF8563_MO_C) ?
+                (tm->tm_year >= 100) : (tm->tm_year < 100);
 
         dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
                 "mday=%d, mon=%d, year=%d, wday=%d\n",
@@ -114,6 +138,7 @@ static int pcf8563_get_datetime(struct i2c_client *client, struct rtc_time *tm)
 
 static int pcf8563_set_datetime(struct i2c_client *client, struct rtc_time *tm)
 {
+        struct pcf8563 *pcf8563 = container_of(client, struct pcf8563, client);
         int i, err;
         unsigned char buf[9];
 
@@ -135,7 +160,7 @@ static int pcf8563_set_datetime(struct i2c_client *client, struct rtc_time *tm)
 
         /* year and century */
         buf[PCF8563_REG_YR] = BIN2BCD(tm->tm_year % 100);
-        if (tm->tm_year < 100)
+        if (pcf8563->c_polarity ? (tm->tm_year >= 100) : (tm->tm_year < 100))
                 buf[PCF8563_REG_MO] |= PCF8563_MO_C;
 
         buf[PCF8563_REG_DW] = tm->tm_wday & 0x07;
@@ -248,6 +273,7 @@ static struct i2c_driver pcf8563_driver = {
 
 static int pcf8563_probe(struct i2c_adapter *adapter, int address, int kind)
 {
+        struct pcf8563 *pcf8563;
         struct i2c_client *client;
         struct rtc_device *rtc;
 
@@ -260,11 +286,12 @@ static int pcf8563_probe(struct i2c_adapter *adapter, int address, int kind)
                 goto exit;
         }
 
-        if (!(client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL))) {
+        if (!(pcf8563 = kzalloc(sizeof(struct pcf8563), GFP_KERNEL))) {
                 err = -ENOMEM;
                 goto exit;
         }
 
+        client = &pcf8563->client;
         client->addr = address;
         client->driver = &pcf8563_driver;
         client->adapter = adapter;
@@ -301,7 +328,7 @@ exit_detach:
         i2c_detach_client(client);
 
 exit_kfree:
-        kfree(client);
+        kfree(pcf8563);
 
 exit:
         return err;
@@ -309,6 +336,7 @@ exit:
 
 static int pcf8563_detach(struct i2c_client *client)
 {
+        struct pcf8563 *pcf8563 = container_of(client, struct pcf8563, client);
         int err;
         struct rtc_device *rtc = i2c_get_clientdata(client);
 
@@ -318,7 +346,7 @@ static int pcf8563_detach(struct i2c_client *client)
         if ((err = i2c_detach_client(client)))
                 return err;
 
-        kfree(client);
+        kfree(pcf8563);
 
         return 0;
 }