[PATCH] scsi: arcmsr: avoid do_gettimeofday

[Arnd Bergmann <arnd@arndb.de>]

The arcmsr uses its own implementation of time_to_tm(), along with do_gettimeofday()
to read the current time. While the algoritm used here is fine in principle, it
suffers from two problems:

- it assigns the seconds portion of the timeval to a 32-bit unsigned integer that
  overflows in 2106 even on 64-bit architectures.
- do_gettimeofday() returns a time_t that overflows in 2038 on all 32-bit systems.

This changes the time retrieval function to ktime_get_real_seconds(), which returns
a proper 64-bit value, and replaces the open-coded time_to_tm() algorithm with
a call to the safe time64_to_tm().

I checked way all numbers are indexed and found that months are given in range
0..11 while the days are in range 1..31, same as 'struct tm', but the year value
that the firmware expects starts in 2000 while 'struct tm' is based on year 1900,
so it needs a small adjustment.

Fixes: b416c099472a ("scsi: arcmsr: Add a function to set date and time to firmware")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/scsi/arcmsr/arcmsr_hba.c | 37 ++++++++++---------------------------
 1 file changed, 10 insertions(+), 27 deletions(-)

diff --git a/drivers/scsi/arcmsr/arcmsr_hba.c b/drivers/scsi/arcmsr/arcmsr_hba.c
index 47745592cff4..75e828bd30e3 100644
--- a/drivers/scsi/arcmsr/arcmsr_hba.c
+++ b/drivers/scsi/arcmsr/arcmsr_hba.c
@@ -3489,8 +3489,9 @@ static int arcmsr_polling_ccbdone(struct AdapterControlBlock *acb,
 static void arcmsr_set_iop_datetime(struct timer_list *t)
 {
 	struct AdapterControlBlock *pacb = from_timer(pacb, t, refresh_timer);
-	unsigned int days, j, i, a, b, c, d, e, m, year, mon, day, hour, min, sec, secs, next_time;
-	struct timeval tv;
+	unsigned int next_time;
+	struct tm tm;
+
 	union {
 		struct	{
 		uint16_t	signature;
@@ -3506,33 +3507,15 @@ static void arcmsr_set_iop_datetime(struct timer_list *t)
 		} b;
 	} datetime;
 
-	do_gettimeofday(&tv);
-	secs = (u32)(tv.tv_sec - (sys_tz.tz_minuteswest * 60));
-	days = secs / 86400;
-	secs = secs - 86400 * days;
-	j = days / 146097;
-	i = days - 146097 * j;
-	a = i + 719468;
-	b = ( 4 * a + 3 ) / 146097;
-	c = a - ( 146097 * b ) / 4;
-	d = ( 4 * c + 3 ) / 1461 ;
-	e = c - ( 1461 * d ) / 4 ;
-	m = ( 5 * e + 2 ) / 153 ;
-	year = 400 * j + 100 * b + d + m / 10 - 2000;
-	mon = m + 3 - 12 * ( m /10 );
-	day = e - ( 153 * m + 2 ) / 5 + 1;
-	hour = secs / 3600;
-	secs = secs - 3600 * hour;
-	min = secs / 60;
-	sec = secs - 60 * min;
+	time64_to_tm(ktime_get_real_seconds(), -sys_tz.tz_minuteswest * 60, &tm);
 
 	datetime.a.signature = 0x55AA;
-	datetime.a.year = year;
-	datetime.a.month = mon;
-	datetime.a.date = day;
-	datetime.a.hour = hour;
-	datetime.a.minute = min;
-	datetime.a.second = sec;
+	datetime.a.year = tm.tm_year - 100; /* base 2000 instead of 1900 */
+	datetime.a.month = tm.tm_mon;
+	datetime.a.date = tm.tm_mday;
+	datetime.a.hour = tm.tm_hour;
+	datetime.a.minute = tm.tm_min;
+	datetime.a.second = tm.tm_sec;
 
 	switch (pacb->adapter_type) {
 		case ACB_ADAPTER_TYPE_A: {
-- 
2.9.0