1 files changed, 16 insertions, 4 deletions

diff --git a/drivers/rtc/rtc-isl12057.c b/drivers/rtc/rtc-isl12057.c
index 8c3f60737df8..b538fabfcfd3 100644
--- a/drivers/rtc/rtc-isl12057.c
+++ b/drivers/rtc/rtc-isl12057.c
@@ -41,6 +41,7 @@
 #define ISL12057_REG_RTC_DW     0x03    /* Day of the Week */
 #define ISL12057_REG_RTC_DT     0x04    /* Date */
 #define ISL12057_REG_RTC_MO     0x05    /* Month */
+#define ISL12057_REG_RTC_MO_CEN BIT(7)  /* Century bit */
 #define ISL12057_REG_RTC_YR     0x06    /* Year */
 #define ISL12057_RTC_SEC_LEN    7
 
@@ -99,24 +100,35 @@ static void isl12057_rtc_regs_to_tm(struct rtc_time *tm, u8 *regs)
         tm->tm_wday = bcd2bin(regs[ISL12057_REG_RTC_DW]) - 1; /* starts at 1 */
         tm->tm_mon  = bcd2bin(regs[ISL12057_REG_RTC_MO] & 0x1f) - 1; /* ditto */
         tm->tm_year = bcd2bin(regs[ISL12057_REG_RTC_YR]) + 100;
+
+        /* Check if years register has overflown from 99 to 00 */
+        if (regs[ISL12057_REG_RTC_MO] & ISL12057_REG_RTC_MO_CEN)
+                tm->tm_year += 100;
 }
 
 static int isl12057_rtc_tm_to_regs(u8 *regs, struct rtc_time *tm)
 {
+        u8 century_bit;
+
         /*
          * The clock has an 8 bit wide bcd-coded register for the year.
+         * It also has a century bit encoded in MO flag which provides
+         * information about overflow of year register from 99 to 00.
          * tm_year is an offset from 1900 and we are interested in the
-         * 2000-2099 range, so any value less than 100 is invalid.
+         * 2000-2199 range, so any value less than 100 or larger than
+         * 299 is invalid.
          */
-        if (tm->tm_year < 100)
+        if (tm->tm_year < 100 || tm->tm_year > 299)
                 return -EINVAL;
 
+        century_bit = (tm->tm_year > 199) ? ISL12057_REG_RTC_MO_CEN : 0;
+
         regs[ISL12057_REG_RTC_SC] = bin2bcd(tm->tm_sec);
         regs[ISL12057_REG_RTC_MN] = bin2bcd(tm->tm_min);
         regs[ISL12057_REG_RTC_HR] = bin2bcd(tm->tm_hour); /* 24-hour format */
         regs[ISL12057_REG_RTC_DT] = bin2bcd(tm->tm_mday);
-        regs[ISL12057_REG_RTC_MO] = bin2bcd(tm->tm_mon + 1);
-        regs[ISL12057_REG_RTC_YR] = bin2bcd(tm->tm_year - 100);
+        regs[ISL12057_REG_RTC_MO] = bin2bcd(tm->tm_mon + 1) | century_bit;
+        regs[ISL12057_REG_RTC_YR] = bin2bcd(tm->tm_year % 100);
         regs[ISL12057_REG_RTC_DW] = bin2bcd(tm->tm_wday + 1);
 
         return 0;