m68k: Use read_persistent_clock64() consistently

We have two ways of getting the current time from a platform at boot
or during suspend: either using read_persistent_clock() or the rtc
class operation. We never need both, so I'm hiding the
read_persistent_clock variant when the generic RTC is enabled.

Since read_persistent_clock() and mktime() are deprecated because of
the y2038 overflow of time_t, we should use the time64_t based
replacements here.

Finally, the dependency on CONFIG_ARCH_USES_GETTIMEOFFSET looks
completely bogus in this case, so let's remove that. It was
added in commit b13b3f5 ("m68k: fix inclusion of
arch_gettimeoffset for non-MMU 68k classic CPU types") to deal
with arch_gettimeoffset(), which has since been removed from
this file and is unrelated to the RTC functions.

The rtc accessors are only used by classic machines, while
coldfire uses proper RTC drivers, so we can put the old
ifdef back around both functions.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

arch/m68k/kernel/time.c

@@ -71,7 +71,9 @@ static irqreturn_t timer_interrupt(int irq, void *dummy)
 	return IRQ_HANDLED;
 }
 
-void read_persistent_clock(struct timespec *ts)
+#ifdef CONFIG_M68KCLASSIC
+#if !IS_BUILTIN(CONFIG_RTC_DRV_GENERIC)
+void read_persistent_clock64(struct timespec64 *ts)
 {
 	struct rtc_time time;
 
@@ -83,11 +85,12 @@ void read_persistent_clock(struct timespec *ts)
 
 	mach_hwclk(0, &time);
 
-	ts->tv_sec = mktime(time.tm_year + 1900, time.tm_mon + 1, time.tm_mday,
-			    time.tm_hour, time.tm_min, time.tm_sec);
+	ts->tv_sec = mktime64(time.tm_year + 1900, time.tm_mon + 1, time.tm_mday,
+			      time.tm_hour, time.tm_min, time.tm_sec);
 }
+#endif
 
-#if defined(CONFIG_ARCH_USES_GETTIMEOFFSET) && IS_ENABLED(CONFIG_RTC_DRV_GENERIC)
+#if IS_ENABLED(CONFIG_RTC_DRV_GENERIC)
 static int rtc_generic_get_time(struct device *dev, struct rtc_time *tm)
 {
 	mach_hwclk(0, tm);
@@ -145,8 +148,8 @@ static int __init rtc_init(void)
 }
 
 module_init(rtc_init);
-
-#endif /* CONFIG_ARCH_USES_GETTIMEOFFSET */
+#endif /* CONFIG_RTC_DRV_GENERIC */
+#endif /* CONFIG M68KCLASSIC */
 
 void __init time_init(void)
 {