[ARM] Add save_time_delta()/restore_time_delta()

These two functions provide the infrastructure to manage time keeping
across a suspend/resume cycle.

arch/arm/kernel/time.c

@@ -304,6 +304,39 @@ int do_settimeofday(struct timespec *tv)
 
 EXPORT_SYMBOL(do_settimeofday);
 
+/**
+ * save_time_delta - Save the offset between system time and RTC time
+ * @delta: pointer to timespec to store delta
+ * @rtc: pointer to timespec for current RTC time
+ *
+ * Return a delta between the system time and the RTC time, such
+ * that system time can be restored later with restore_time_delta()
+ */
+void save_time_delta(struct timespec *delta, struct timespec *rtc)
+{
+	set_normalized_timespec(delta,
+				xtime.tv_sec - rtc->tv_sec,
+				xtime.tv_nsec - rtc->tv_nsec);
+}
+EXPORT_SYMBOL(save_time_delta);
+
+/**
+ * restore_time_delta - Restore the current system time
+ * @delta: delta returned by save_time_delta()
+ * @rtc: pointer to timespec for current RTC time
+ */
+void restore_time_delta(struct timespec *delta, struct timespec *rtc)
+{
+	struct timespec ts;
+
+	set_normalized_timespec(&ts,
+				delta->tv_sec + rtc->tv_sec,
+				delta->tv_nsec + rtc->tv_nsec);
+
+	do_settimeofday(&ts);
+}
+EXPORT_SYMBOL(restore_time_delta);
+
 void timer_tick(struct pt_regs *regs)
 {
 	profile_tick(CPU_PROFILING, regs);

arch/arm/mach-pxa/pm.c

@@ -21,6 +21,7 @@
 #include <asm/system.h>
 #include <asm/arch/pxa-regs.h>
 #include <asm/arch/lubbock.h>
+#include <asm/mach/time.h>
 
 
 /*
@@ -69,14 +70,16 @@ static int pxa_pm_enter(u32 state)
 {
 	unsigned long sleep_save[SLEEP_SAVE_SIZE];
 	unsigned long checksum = 0;
-	unsigned long delta;
+	struct timespec delta, rtc;
 	int i;
 
 	if (state != PM_SUSPEND_MEM)
 		return -EINVAL;
 
 	/* preserve current time */
-	delta = xtime.tv_sec - RCNR;
+	rtc.tv_sec = RCNR;
+	rtc.tv_nsec = 0;
+	save_time_delta(&delta, &rtc);
 
 	/* save vital registers */
 	SAVE(OSMR0);
@@ -161,7 +164,8 @@ static int pxa_pm_enter(u32 state)
 	RESTORE(ICMR);
 
 	/* restore current time */
-	xtime.tv_sec = RCNR + delta;
+	rtc.tv_sec = RCNR;
+	restore_time_delta(&delta, &rtc);
 
 #ifdef DEBUG
 	printk(KERN_DEBUG "*** made it back from resume\n");

arch/arm/mach-sa1100/pm.c

@@ -30,6 +30,7 @@
 #include <asm/hardware.h>
 #include <asm/memory.h>
 #include <asm/system.h>
+#include <asm/mach/time.h>
 
 extern void sa1100_cpu_suspend(void);
 extern void sa1100_cpu_resume(void);
@@ -58,14 +59,16 @@ enum {	SLEEP_SAVE_SP = 0,
 
 static int sa11x0_pm_enter(u32 state)
 {
-	unsigned long sleep_save[SLEEP_SAVE_SIZE];
-	unsigned long delta, gpio;
+	unsigned long gpio, sleep_save[SLEEP_SAVE_SIZE];
+	struct timespec delta, rtc;
 
 	if (state != PM_SUSPEND_MEM)
 		return -EINVAL;
 
 	/* preserve current time */
-	delta = xtime.tv_sec - RCNR;
+	rtc.tv_sec = RCNR;
+	rtc.tv_nsec = 0;
+	save_time_delta(&delta, &rtc);
 	gpio = GPLR;
 
 	/* save vital registers */
@@ -136,7 +139,8 @@ static int sa11x0_pm_enter(u32 state)
 	OSCR = OSMR0 - LATCH;
 
 	/* restore current time */
-	xtime.tv_sec = RCNR + delta;
+	rtc.tv_sec = RCNR;
+	restore_time_delta(&delta, &rtc);
 
 	return 0;
 }

include/asm-arm/mach/time.h

@@ -13,8 +13,11 @@
 extern void (*init_arch_time)(void);
 
 extern int (*set_rtc)(void);
-extern unsigned long(*gettimeoffset)(void);
+extern unsigned long (*gettimeoffset)(void);
 
-void timer_tick(struct pt_regs *);
+extern void timer_tick(struct pt_regs *);
+
+extern void save_time_delta(struct timespec *delta, struct timespec *rtc);
+extern void restore_time_delta(struct timespec *delta, struct timespec *rtc);
 
 #endif