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Subject[patch 6/6] rtc suspend()/resume() restores system clock
Date
RTC class suspend/resume support, re-initializing the system clock on resume
from the clock used to initialize it at boot time.

- Inlining the same code used by ARM, which saves and restores the
delta between a selected RTC and the current system wall-clock time.

- Removes calls to that ARM code from AT91, OMAP, and S3C RTCs.

This goes on top of the patch series removing "struct class_device" usage
from the RTC framework. That makes class suspend()/resume() work.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

---
drivers/rtc/Kconfig | 24 +++++++++----
drivers/rtc/class.c | 74 +++++++++++++++++++++++++++++++++++++++++++
drivers/rtc/rtc-at91rm9200.c | 30 -----------------
drivers/rtc/rtc-omap.c | 17 ---------
drivers/rtc/rtc-s3c.c | 22 ------------
5 files changed, 91 insertions(+), 76 deletions(-)
Index: at91/drivers/rtc/Kconfig
===================================================================
--- at91.orig/drivers/rtc/Kconfig 2007-02-21 18:47:38.000000000 -0800
+++ at91/drivers/rtc/Kconfig 2007-02-21 18:47:41.000000000 -0800
@@ -21,21 +21,31 @@ config RTC_CLASS
will be called rtc-class.

config RTC_HCTOSYS
- bool "Set system time from RTC on startup"
+ bool "Set system time from RTC on startup and resume"
depends on RTC_CLASS = y
default y
help
- If you say yes here, the system time will be set using
- the value read from the specified RTC device. This is useful
- in order to avoid unnecessary fsck runs.
+ If you say yes here, the system time (wall clock) will be set using
+ the value read from a specified RTC device. This is useful to avoid
+ unnecessary fsck runs at boot time, and to network better.

config RTC_HCTOSYS_DEVICE
- string "The RTC to read the time from"
+ string "RTC used to set the system time"
depends on RTC_HCTOSYS = y
default "rtc0"
help
- The RTC device that will be used as the source for
- the system time, usually rtc0.
+ The RTC device that will be used to (re)initialize the system
+ clock, usually rtc0. Initialization is done when the system
+ starts up, and when it resumes from a low power state.
+
+ This clock should be battery-backed, so that it reads the correct
+ time when the system boots from a power-off state. Otherwise, your
+ system will need an external clock source (like an NTP server).
+
+ If the clock you specify here is not battery backed, it may still
+ be useful to reinitialize system time when resuming from system
+ sleep states. Do not specify an RTC here unless it stays powered
+ during all this system's supported sleep states.

config RTC_DEBUG
bool "RTC debug support"
Index: at91/drivers/rtc/class.c
===================================================================
--- at91.orig/drivers/rtc/class.c 2007-02-21 18:47:39.000000000 -0800
+++ at91/drivers/rtc/class.c 2007-02-21 18:47:41.000000000 -0800
@@ -32,6 +32,78 @@ static void rtc_device_release(struct de
kfree(rtc);
}

+#if defined(CONFIG_PM) && defined(CONFIG_RTC_HCTOSYS_DEVICE)
+
+/*
+ * On suspend(), measure the delta between one RTC and the
+ * system's wall clock; restore it on resume().
+ */
+
+static struct timespec delta;
+static time_t oldtime;
+
+static int rtc_suspend(struct device *dev, pm_message_t mesg)
+{
+ struct rtc_device *rtc = to_rtc_device(dev);
+ struct rtc_time tm;
+
+ if (strncmp(rtc->dev.bus_id,
+ CONFIG_RTC_HCTOSYS_DEVICE,
+ BUS_ID_SIZE) != 0)
+ return 0;
+
+ rtc_read_time(rtc, &tm);
+ rtc_tm_to_time(&tm, &oldtime);
+
+ /* RTC precision is 1 second; adjust delta for avg 1/2 sec err */
+ set_normalized_timespec(&delta,
+ xtime.tv_sec - oldtime,
+ xtime.tv_nsec - (NSEC_PER_SEC >> 1));
+
+ return 0;
+}
+
+static int rtc_resume(struct device *dev)
+{
+ struct rtc_device *rtc = to_rtc_device(dev);
+ struct rtc_time tm;
+ time_t newtime;
+ struct timespec time;
+
+ if (strncmp(rtc->dev.bus_id,
+ CONFIG_RTC_HCTOSYS_DEVICE,
+ BUS_ID_SIZE) != 0)
+ return 0;
+
+ rtc_read_time(rtc, &tm);
+ if (rtc_valid_tm(&tm) != 0) {
+ pr_debug("%s: bogus resume time\n", rtc->dev.bus_id);
+ return 0;
+ }
+ rtc_tm_to_time(&tm, &newtime);
+ if (newtime <= oldtime) {
+ if (newtime < oldtime)
+ pr_debug("%s: time travel!\n", rtc->dev.bus_id);
+ return 0;
+ }
+
+ /* restore wall clock using delta against this RTC;
+ * adjust again for avg 1/2 second RTC sampling error
+ */
+ set_normalized_timespec(&time,
+ newtime + delta.tv_sec,
+ (NSEC_PER_SEC >> 1) + delta.tv_nsec);
+ do_settimeofday(&time);
+
+ return 0;
+}
+
+#else
+#define rtc_suspend NULL
+#define rtc_resume NULL
+#endif
+
+
/**
* rtc_device_register - register w/ RTC class
* @dev: the device to register
@@ -138,6 +210,8 @@ static int __init rtc_init(void)
printk(KERN_ERR "%s: couldn't create class\n", __FILE__);
return PTR_ERR(rtc_class);
}
+ rtc_class->suspend = rtc_suspend;
+ rtc_class->resume = rtc_resume;
rtc_dev_init();
rtc_sysfs_init(rtc_class);
return 0;
Index: at91/drivers/rtc/rtc-at91rm9200.c
===================================================================
--- at91.orig/drivers/rtc/rtc-at91rm9200.c 2007-02-21 18:47:26.000000000 -0800
+++ at91/drivers/rtc/rtc-at91rm9200.c 2007-02-21 18:47:41.000000000 -0800
@@ -348,21 +348,10 @@ static int __exit at91_rtc_remove(struct

/* AT91RM9200 RTC Power management control */

-static struct timespec at91_rtc_delta;
static u32 at91_rtc_imr;

static int at91_rtc_suspend(struct platform_device *pdev, pm_message_t state)
{
- struct rtc_time tm;
- struct timespec time;
-
- time.tv_nsec = 0;
-
- /* calculate time delta for suspend */
- at91_rtc_readtime(&pdev->dev, &tm);
- rtc_tm_to_time(&tm, &time.tv_sec);
- save_time_delta(&at91_rtc_delta, &time);
-
/* this IRQ is shared with DBGU and other hardware which isn't
* necessarily doing PM like we are...
*/
@@ -374,36 +363,17 @@ static int at91_rtc_suspend(struct platf
else
at91_sys_write(AT91_RTC_IDR, at91_rtc_imr);
}
-
- pr_debug("%s(): %4d-%02d-%02d %02d:%02d:%02d\n", __FUNCTION__,
- 1900 + tm.tm_year, tm.tm_mon, tm.tm_mday,
- tm.tm_hour, tm.tm_min, tm.tm_sec);
-
return 0;
}

static int at91_rtc_resume(struct platform_device *pdev)
{
- struct rtc_time tm;
- struct timespec time;
-
- time.tv_nsec = 0;
-
- at91_rtc_readtime(&pdev->dev, &tm);
- rtc_tm_to_time(&tm, &time.tv_sec);
- restore_time_delta(&at91_rtc_delta, &time);
-
if (at91_rtc_imr) {
if (device_may_wakeup(&pdev->dev))
disable_irq_wake(AT91_ID_SYS);
else
at91_sys_write(AT91_RTC_IER, at91_rtc_imr);
}
-
- pr_debug("%s(): %4d-%02d-%02d %02d:%02d:%02d\n", __FUNCTION__,
- 1900 + tm.tm_year, tm.tm_mon, tm.tm_mday,
- tm.tm_hour, tm.tm_min, tm.tm_sec);
-
return 0;
}
#else
Index: at91/drivers/rtc/rtc-omap.c
===================================================================
--- at91.orig/drivers/rtc/rtc-omap.c 2007-02-21 18:47:39.000000000 -0800
+++ at91/drivers/rtc/rtc-omap.c 2007-02-21 18:47:41.000000000 -0800
@@ -488,19 +488,10 @@ static int __devexit omap_rtc_remove(str

#ifdef CONFIG_PM

-static struct timespec rtc_delta;
static u8 irqstat;

static int omap_rtc_suspend(struct platform_device *pdev, pm_message_t state)
{
- struct rtc_time rtc_tm;
- struct timespec time;
-
- time.tv_nsec = 0;
- omap_rtc_read_time(NULL, &rtc_tm);
- rtc_tm_to_time(&rtc_tm, &time.tv_sec);
-
- save_time_delta(&rtc_delta, &time);
irqstat = rtc_read(OMAP_RTC_INTERRUPTS_REG);

/* FIXME the RTC alarm is not currently acting as a wakeup event
@@ -517,14 +508,6 @@ static int omap_rtc_suspend(struct platf

static int omap_rtc_resume(struct platform_device *pdev)
{
- struct rtc_time rtc_tm;
- struct timespec time;
-
- time.tv_nsec = 0;
- omap_rtc_read_time(NULL, &rtc_tm);
- rtc_tm_to_time(&rtc_tm, &time.tv_sec);
-
- restore_time_delta(&rtc_delta, &time);
if (device_may_wakeup(&pdev->dev))
disable_irq_wake(omap_rtc_alarm);
else
Index: at91/drivers/rtc/rtc-s3c.c
===================================================================
--- at91.orig/drivers/rtc/rtc-s3c.c 2007-02-21 18:47:26.000000000 -0800
+++ at91/drivers/rtc/rtc-s3c.c 2007-02-21 18:47:41.000000000 -0800
@@ -548,37 +548,15 @@ static int ticnt_save;

static int s3c_rtc_suspend(struct platform_device *pdev, pm_message_t state)
{
- struct rtc_time tm;
- struct timespec time;
-
- time.tv_nsec = 0;
-
/* save TICNT for anyone using periodic interrupts */
-
ticnt_save = readb(s3c_rtc_base + S3C2410_TICNT);
-
- /* calculate time delta for suspend */
-
- s3c_rtc_gettime(&pdev->dev, &tm);
- rtc_tm_to_time(&tm, &time.tv_sec);
- save_time_delta(&s3c_rtc_delta, &time);
s3c_rtc_enable(pdev, 0);
-
return 0;
}

static int s3c_rtc_resume(struct platform_device *pdev)
{
- struct rtc_time tm;
- struct timespec time;
-
- time.tv_nsec = 0;
-
s3c_rtc_enable(pdev, 1);
- s3c_rtc_gettime(&pdev->dev, &tm);
- rtc_tm_to_time(&tm, &time.tv_sec);
- restore_time_delta(&s3c_rtc_delta, &time);
-
writeb(ticnt_save, s3c_rtc_base + S3C2410_TICNT);
return 0;
}
-
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