[PATCH 1/5] powerpc: generic time suspend/resume code

[Guennadi Liakhovetski]

On Mon, 19 Mar 2007, Johannes Berg wrote:

> It's not just the generic RTC suspend code that is relevant but also the
> ppc_md rtc hooks, ultimately they probably should be removed totally
> once powerpc completely migrates to genrtc everywhere. In the patch you
> showed me to this file you actually circumvented the ppc_md rtc hooks
> because you're already using genrtc, in that case the genrtc suspend
> code is obviously much more appropriate.

Just to make it easier for everyone to follow below is my patch I showed 
Johannes today on IRC. I use it atm on the top of his patch to save / 
restore system time. Notice, it is not thought for upstream in any way - 
just for reference.

Another point I forgot to mention in my first reply - why does this patch 
use a special mechanism to restore the time like saving the rtc time on 
suspend, re-reading it on resume, calculating the difference and adding it 
to the current timeofday, which is, presumably, equal to suspend time? 
Isn't re-using the same method as on poweron of setting the timeofday from 
rtc more logical? Which is exactly what David's patch does?

Thanks
Guennadi
---
Guennadi Liakhovetski

(not for inclusion, for reference only, hence no "Signed-off-by")

--- a/arch/powerpc/sysdev/timer.c	2007-03-19 22:26:12.000000000 +0100
+++ b/arch/powerpc/sysdev/timer.c	2007-03-03 01:19:01.000000000 +0100
@@ -11,6 +11,24 @@
 
 static unsigned long suspend_rtc_time;
 
+static int timer_get_rtc_time(struct rtc_time *time)
+{
+	int err = 0;
+
+	if (ppc_md.get_rtc_time)
+		get_rtc_time(time);
+	else {
+		struct class_device *class_dev = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);
+
+		WARN_ON(!class_dev);
+
+		err = rtc_read_time(class_dev, time);
+		rtc_class_close(class_dev);
+	}
+
+	return err;
+}
+
 /*
  * Reset the time after a sleep.
  */
@@ -20,9 +38,12 @@
 	struct timespec ts;
 	struct rtc_time cur_rtc_tm;
 	unsigned long cur_rtc_time, diff;
+	int err;
 
 	/* get current RTC time and convert to seconds */
-	get_rtc_time(&cur_rtc_tm);
+	err = timer_get_rtc_time(&cur_rtc_tm);
+	if (err)
+		return err;
 	rtc_tm_to_time(&cur_rtc_tm, &cur_rtc_time);
 
 	diff = cur_rtc_time - suspend_rtc_time;
@@ -40,9 +61,11 @@
 static int timer_suspend(struct sys_device *dev, pm_message_t state)
 {
 	struct rtc_time suspend_rtc_tm;
-	WARN_ON(!ppc_md.get_rtc_time);
+	int err;
 
-	get_rtc_time(&suspend_rtc_tm);
+	err = timer_get_rtc_time(&suspend_rtc_tm);
+	if (err)
+		return err;
 	rtc_tm_to_time(&suspend_rtc_tm, &suspend_rtc_time);
 
 	return 0;