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SubjectRe: [RFC][PATCH] Unify interface to persistent CMOS/RTC/whatever clock
Date
On Saturday 19 August 2006 9:39 am, David Brownell wrote:
> > So if we go w/ the "it may not be available, so always assume it isn't"
> > way of thinking, it forces us to rely upon the RTC driver(s) to resume
> > time (which means every RTC, no matter how simple has to have
> > suspend/resume hooks and call settimeofday at least).
>
> No, that was the point of my comment about using the new class level
> suspend/resume calls. The RTC drivers wouldn't be responsible for
> that; the RTC framework would be. RTC drivers may still want the
> suspend/resume hooks to make sure they issue system wakeup events,
> and so on, but no longer for maintaining the wall clock. I'll send
> a patch (of the "it compiles" type) later.

Welcome to "later"!

------------------------

Preliminary RTC class suspend/resume support:

- Inlining the same code used by ARM, save and restore the delta between
a selected RTC and the current system time.

- Removes calls to that ARM code from the AT91 and S3C RTCs; the AT91
calls are left as stubs, because a pending patch still needs those
(currently empty) routines to properly issue system wakeup events.

- Selects rtc0 by default, else CONFIG_RTC_HCTOSYS_DEVICE. We expect all RTCs
to be powered during "real" sleep states, but swsusp/hibernation requires
something that's also battery-backed.

Depends on new class suspend/resume methods, added by a patch in the MM tree.

(Preliminary because untested, and because of a FIXME ... nothing recovers
from unregistering the selected RTC; that could happen only with badly written
RTC drivers though.)


Index: g26/drivers/rtc/class.c
===================================================================
--- g26.orig/drivers/rtc/class.c 2006-08-19 09:20:36.000000000 -0700
+++ g26/drivers/rtc/class.c 2006-08-19 09:20:37.000000000 -0700
@@ -29,6 +29,86 @@ static void rtc_device_release(struct cl
kfree(rtc);
}

+#ifdef CONFIG_PM
+
+/*
+ * Re-initialize wall clock on resume, to match the delta (calculated
+ * during suspend) between that and an appropriate RTC.
+ *
+ * We assume any RTC is good enough, meaning it stays running during
+ * system sleep states; but prefer the CONFIG_RTC_HCTOSYS_DEVICE on
+ * the grounds that it's expected to be battery-backed and thus will
+ * stay running even during the "off" states used by swsusp.
+ *
+ * REVISIT ... we should probably have a way to tell if a given RTC
+ * will stay powered during the target system state, rather than just
+ * assume a "valid" configuration (where no RTC that powers off will
+ * be selected, and no selected RTC will be removed). That could let
+ * us get rid of the need for CONFIG_RTC_HCTOSYS_DEVICE too...
+ */
+
+static struct class_device *sleep_rtc;
+static struct timespec delta;
+
+static int rtc_suspend(struct device *dev, pm_message_t mesg)
+{
+ struct rtc_time tm;
+ struct timespec time;
+
+ if (!sleep_rtc || dev != sleep_rtc->dev)
+ return 0;
+
+ time.tv_nsec = 0;
+
+ rtc_read_time(sleep_rtc, &tm);
+ rtc_tm_to_time(&tm, &time.tv_sec);
+
+ set_normalized_timespec(&delta,
+ xtime.tv_sec - time.tv_sec,
+ xtime.tv_nsec - time.tv_nsec);
+
+ pr_debug("%s: %s %4d-%02d-%02d %02d:%02d:%02d\n",
+ sleep_rtc->class_id, "suspend",
+ 1900 + tm.tm_year, tm.tm_mon, tm.tm_mday,
+ tm.tm_hour, tm.tm_min, tm.tm_sec);
+
+ return 0;
+}
+
+static int rtc_resume(struct device *dev)
+{
+ struct rtc_time tm;
+ struct timespec time;
+
+ /* REVISIT some swsusp configurations may feed us an RTC that
+ * lost power ... we should probably try detecting that, and
+ * refuse to update the time using a bogus clock.
+ */
+
+ if (!sleep_rtc || dev != sleep_rtc->dev)
+ return 0;
+
+ time.tv_nsec = 0;
+
+ rtc_read_time(sleep_rtc, &tm);
+ rtc_tm_to_time(&tm, &time.tv_sec);
+
+ set_normalized_timespec(&time,
+ xtime.tv_sec - time.tv_sec,
+ xtime.tv_nsec - time.tv_nsec);
+ do_settimeofday(&time);
+
+ pr_debug("%s: %s %4d-%02d-%02d %02d:%02d:%02d\n",
+ sleep_rtc->class_id, "resume",
+ 1900 + tm.tm_year, tm.tm_mon, tm.tm_mday,
+ tm.tm_hour, tm.tm_min, tm.tm_sec);
+
+ return 0;
+}
+
+#endif
+
+
/**
* rtc_device_register - register w/ RTC class
* @dev: the device to register
@@ -85,6 +165,21 @@ struct rtc_device *rtc_device_register(c
if (err)
goto exit_kfree;

+#ifdef CONFIG_PM
+ mutex_lock(&idr_lock);
+#ifdef CONFIG_RTC_HCTOSYS_DEVICE
+ if (sleep_rtc && strncmp(rtc->class_dev.class_id,
+ CONFIG_RTC_HCTOSYS_DEVICE,
+ BUS_ID_SIZE) == 0) {
+ rtc_class_close(sleep_rtc);
+ sleep_rtc = NULL;
+ }
+#endif
+ if (!sleep_rtc)
+ sleep_rtc = rtc_class_open(rtc->class_dev.class_id);
+ mutex_unlock(&idr_lock);
+#endif
+
dev_info(dev, "rtc core: registered %s as %s\n",
rtc->name, rtc->class_dev.class_id);

@@ -113,6 +208,17 @@ EXPORT_SYMBOL_GPL(rtc_device_register);
*/
void rtc_device_unregister(struct rtc_device *rtc)
{
+#ifdef CONFIG_PM
+ mutex_lock(&idr_lock);
+ if (&rtc->class_dev == sleep_rtc) {
+ rtc_class_close(sleep_rtc);
+ sleep_rtc = NULL;
+ /* FIXME */
+ printk(KERN_WARNING "rtc: now what to use during sleep??\n");
+ }
+ mutex_unlock(&idr_lock);
+#endif
+
mutex_lock(&rtc->ops_lock);
rtc->ops = NULL;
mutex_unlock(&rtc->ops_lock);
@@ -134,6 +240,10 @@ static int __init rtc_init(void)
printk(KERN_ERR "%s: couldn't create class\n", __FILE__);
return PTR_ERR(rtc_class);
}
+#ifdef CONFIG_PM
+ rtc_class->suspend = rtc_suspend;
+ rtc_class->resume = rtc_resume;
+#endif
return 0;
}

Index: g26/drivers/rtc/rtc-at91.c
===================================================================
--- g26.orig/drivers/rtc/rtc-at91.c 2006-08-19 09:20:36.000000000 -0700
+++ g26/drivers/rtc/rtc-at91.c 2006-08-19 09:20:37.000000000 -0700
@@ -339,38 +339,13 @@ static struct timespec at91_rtc_delta;

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);
-
- 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);
-
+ /* STUB, pending merge of rtc wakeup patch */
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);
-
- 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);
-
+ /* STUB, pending merge of rtc wakeup patch */
return 0;
}
#else
Index: g26/drivers/rtc/rtc-s3c.c
===================================================================
--- g26.orig/drivers/rtc/rtc-s3c.c 2006-08-19 09:20:36.000000000 -0700
+++ g26/drivers/rtc/rtc-s3c.c 2006-08-19 09:20:37.000000000 -0700
@@ -536,37 +536,15 @@ 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(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, S3C2410_TICNT);
return 0;
}
-
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