isdn: Use ktime_t instead of 'struct timeval'

'struct timeval' uses 32-bit representation for seconds which will
overflow in year 2038 and beyond. mISDN/clock.c needs to compute and
store elapsed time in intervals of 125 microseconds. This patch replaces
the usage of 'struct timeval' with 64-bit ktime_t which is y2038 safe.
The patch also replaces do_gettimeofday() (wall-clock time) with
ktime_get() (monotonic time) since we only care about elapsed time here.

Signed-off-by: Tina Ruchandani <ruchandani.tina@gmail.com>
Suggested-by: Arnd Bergmnann <arnd@arndb.de>
Suggested-by: David Miller <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 29 insertions, 40 deletions

diff --git a/drivers/isdn/mISDN/clock.c b/drivers/isdn/mISDN/clock.c
index 693fb7c9b59a..f8f659f1ce1b 100644
--- a/drivers/isdn/mISDN/clock.c
+++ b/drivers/isdn/mISDN/clock.c
@@ -37,6 +37,7 @@
 #include <linux/types.h>
 #include <linux/stddef.h>
 #include <linux/spinlock.h>
+#include <linux/ktime.h>
 #include <linux/mISDNif.h>
 #include <linux/export.h>
 #include "core.h"
@@ -45,15 +46,15 @@ static u_int *debug;
 static LIST_HEAD(iclock_list);
 static DEFINE_RWLOCK(iclock_lock);
 static u16 iclock_count;                /* counter of last clock */
-static struct timeval iclock_tv;        /* time stamp of last clock */
-static int iclock_tv_valid;             /* already received one timestamp */
+static ktime_t iclock_timestamp;        /* time stamp of last clock */
+static int iclock_timestamp_valid;      /* already received one timestamp */
 static struct mISDNclock *iclock_current;
 
 void
 mISDN_init_clock(u_int *dp)
 {
         debug = dp;
-        do_gettimeofday(&iclock_tv);
+        iclock_timestamp = ktime_get();
 }
 
 static void
@@ -86,7 +87,7 @@ select_iclock(void)
         }
         if (bestclock != iclock_current) {
                 /* no clock received yet */
-                iclock_tv_valid = 0;
+                iclock_timestamp_valid = 0;
         }
         iclock_current = bestclock;
 }
@@ -139,12 +140,11 @@ mISDN_unregister_clock(struct mISDNclock *iclock)
 EXPORT_SYMBOL(mISDN_unregister_clock);
 
 void
-mISDN_clock_update(struct mISDNclock *iclock, int samples, struct timeval *tv)
+mISDN_clock_update(struct mISDNclock *iclock, int samples, ktime_t *timestamp)
 {
         u_long          flags;
-        struct timeval  tv_now;
-        time_t          elapsed_sec;
-        int             elapsed_8000th;
+        ktime_t         timestamp_now;
+        u16             delta;
 
         write_lock_irqsave(&iclock_lock, flags);
         if (iclock_current != iclock) {
@@ -156,33 +156,27 @@ mISDN_clock_update(struct mISDNclock *iclock, int samples, struct timeval *tv)
                 write_unlock_irqrestore(&iclock_lock, flags);
                 return;
         }
-        if (iclock_tv_valid) {
+        if (iclock_timestamp_valid) {
                 /* increment sample counter by given samples */
                 iclock_count += samples;
-                if (tv) { /* tv must be set, if function call is delayed */
-                        iclock_tv.tv_sec = tv->tv_sec;
-                        iclock_tv.tv_usec = tv->tv_usec;
-                } else
-                        do_gettimeofday(&iclock_tv);
+                if (timestamp) { /* timestamp must be set, if function call is delayed */
+                        iclock_timestamp = *timestamp;
+                } else  {
+                        iclock_timestamp = ktime_get();
+                }
         } else {
                 /* calc elapsed time by system clock */
-                if (tv) { /* tv must be set, if function call is delayed */
-                        tv_now.tv_sec = tv->tv_sec;
-                        tv_now.tv_usec = tv->tv_usec;
-                } else
-                        do_gettimeofday(&tv_now);
-                elapsed_sec = tv_now.tv_sec - iclock_tv.tv_sec;
-                elapsed_8000th = (tv_now.tv_usec / 125)
-                        - (iclock_tv.tv_usec / 125);
-                if (elapsed_8000th < 0) {
-                        elapsed_sec -= 1;
-                        elapsed_8000th += 8000;
+                if (timestamp) { /* timestamp must be set, if function call is delayed */
+                        timestamp_now = *timestamp;
+                } else {
+                        timestamp_now = ktime_get();
                 }
+                delta = ktime_divns(ktime_sub(timestamp_now, iclock_timestamp),
+                                (NSEC_PER_SEC / 8000));
                 /* add elapsed time to counter and set new timestamp */
-                iclock_count += elapsed_sec * 8000 + elapsed_8000th;
-                iclock_tv.tv_sec = tv_now.tv_sec;
-                iclock_tv.tv_usec = tv_now.tv_usec;
-                iclock_tv_valid = 1;
+                iclock_count += delta;
+                iclock_timestamp = timestamp_now;
+                iclock_timestamp_valid = 1;
                 if (*debug & DEBUG_CLOCK)
                         printk("Received first clock from source '%s'.\n",
                                iclock_current ? iclock_current->name : "nothing");
@@ -195,22 +189,17 @@ unsigned short
 mISDN_clock_get(void)
 {
         u_long          flags;
-        struct timeval  tv_now;
-        time_t          elapsed_sec;
-        int             elapsed_8000th;
+        ktime_t         timestamp_now;
+        u16             delta;
         u16             count;
 
         read_lock_irqsave(&iclock_lock, flags);
         /* calc elapsed time by system clock */
-        do_gettimeofday(&tv_now);
-        elapsed_sec = tv_now.tv_sec - iclock_tv.tv_sec;
-        elapsed_8000th = (tv_now.tv_usec / 125) - (iclock_tv.tv_usec / 125);
-        if (elapsed_8000th < 0) {
-                elapsed_sec -= 1;
-                elapsed_8000th += 8000;
-        }
+        timestamp_now = ktime_get();
+        delta = ktime_divns(ktime_sub(timestamp_now, iclock_timestamp),
+                        (NSEC_PER_SEC / 8000));
         /* add elapsed time to counter */
-        count = iclock_count + elapsed_sec * 8000 + elapsed_8000th;
+        count = iclock_count + delta;
         read_unlock_irqrestore(&iclock_lock, flags);
         return count;
 }