From patchwork Tue Feb 22 20:49:56 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Stultz X-Patchwork-Id: 202 Return-Path: Delivered-To: unknown Received: from imap.gmail.com (74.125.159.109) by localhost6.localdomain6 with IMAP4-SSL; 08 Jun 2011 14:40:49 -0000 Delivered-To: patches@linaro.org Received: by 10.224.19.208 with SMTP id c16cs257735qab; Tue, 22 Feb 2011 12:50:32 -0800 (PST) Received: by 10.229.182.196 with SMTP id cd4mr2373227qcb.215.1298407831874; Tue, 22 Feb 2011 12:50:31 -0800 (PST) Received: from e35.co.us.ibm.com (e35.co.us.ibm.com [32.97.110.153]) by mx.google.com with ESMTPS id q5si13756615qcs.135.2011.02.22.12.50.31 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 22 Feb 2011 12:50:31 -0800 (PST) Received-SPF: pass (google.com: domain of jstultz@us.ibm.com designates 32.97.110.153 as permitted sender) client-ip=32.97.110.153; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jstultz@us.ibm.com designates 32.97.110.153 as permitted sender) smtp.mail=jstultz@us.ibm.com Received: from d03relay01.boulder.ibm.com (d03relay01.boulder.ibm.com [9.17.195.226]) by e35.co.us.ibm.com (8.14.4/8.13.1) with ESMTP id p1MKZrTt030638; Tue, 22 Feb 2011 13:35:53 -0700 Received: from d03av03.boulder.ibm.com (d03av03.boulder.ibm.com [9.17.195.169]) by d03relay01.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p1MKoMiw087884; Tue, 22 Feb 2011 13:50:22 -0700 Received: from d03av03.boulder.ibm.com (loopback [127.0.0.1]) by d03av03.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p1MKoLRF019157; Tue, 22 Feb 2011 13:50:22 -0700 Received: from kernel.beaverton.ibm.com (kernel.beaverton.ibm.com [9.47.67.96]) by d03av03.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id p1MKoLOn019142; Tue, 22 Feb 2011 13:50:21 -0700 Received: by kernel.beaverton.ibm.com (Postfix, from userid 1056) id 10E561E750E; Tue, 22 Feb 2011 12:50:21 -0800 (PST) From: John Stultz To: LKML Cc: John Stultz , Mark Brown , Marcelo Roberto Jimenez , Thomas Gleixner , Alessandro Zummo , rtc-linux@googlegroups.com, patches@linaro.org Subject: [PATCH][RFC] RTC: Initialize kernel state from RTC Date: Tue, 22 Feb 2011 12:49:56 -0800 Message-Id: <1298407796-28010-1-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.7.3.2.146.gca209 Just wanted to send this out for initial comment. It would be great if someone with RTC hardware that preserves alarm state across resets could test this. I've tested with cmos and we correctly preserve the alarm time value, but because of the hardware the alarm is not enabled after reset. If there's no objections, I'll try to squeeze this fix into 2.6.38 (although its frustratingly large for this late in the cycle, so it might have to wait until 2.6.38.1). thanks -john Mark Brown pointed out a coner case: that RTC alarms should be allowed to be persistent across reboots if the hardware supported it. The rework of the generic layer to virtualize the RTC alarm virtualized much of the alarm handling, and removed the code used to read the alarm time from the hardware. Mark noted if we want the alarm to be persistent across reboots, we need to re-read the alarm value into the virtualized generic layer at boot up, so that the generic layer properly exposes that value. This patch restores much of the earlier removed rtc_read_alarm code and wires it in so that we set the kernel's alarm value to what we find in the hardware at boot time. NOTE: Not all hardware supports persistent RTC alarm state across system reset. rtc-cmos for example will keep the alarm time, but disables the AIE mode irq. Applications should not expect the RTC alarm to be valid after a system reset. We will preserve what we can, to represent the hardware state at boot, but its not guarenteed. Further, in the future, with multiplexed RTC alarms, the soonest alarm to fire may not be the one set via the /dev/rt ioctls. So an application may set the alarm with RTC_ALM_SET, but after a reset find that RTC_ALM_READ returns an earlier time. Again, we preserve what we can, but applications should not expect the RTC alarm state to persist across a system reset. Big thanks to Mark for pointing out the issue! Thanks also to Marcelo for helping think through the solution. CC: Mark Brown CC: Marcelo Roberto Jimenez CC: Thomas Gleixner CC: Alessandro Zummo CC: rtc-linux@googlegroups.com CC: patches@linaro.org Reported-by: Mark Brown Signed-off-by: John Stultz --- drivers/rtc/class.c | 7 ++ drivers/rtc/interface.c | 180 +++++++++++++++++++++++++++++++++++++++++++++++ include/linux/rtc.h | 1 + 3 files changed, 188 insertions(+), 0 deletions(-) diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c index c404b61..09b4437 100644 --- a/drivers/rtc/class.c +++ b/drivers/rtc/class.c @@ -117,6 +117,7 @@ struct rtc_device *rtc_device_register(const char *name, struct device *dev, struct module *owner) { struct rtc_device *rtc; + struct rtc_wkalrm alrm; int id, err; if (idr_pre_get(&rtc_idr, GFP_KERNEL) == 0) { @@ -166,6 +167,12 @@ struct rtc_device *rtc_device_register(const char *name, struct device *dev, rtc->pie_timer.function = rtc_pie_update_irq; rtc->pie_enabled = 0; + /* Check to see if there is an ALARM already set in hw */ + err = __rtc_read_alarm(rtc, &alrm); + + if (!err && !rtc_valid_tm(&alrm.time)) + rtc_set_alarm(rtc, &alrm); + strlcpy(rtc->name, name, RTC_DEVICE_NAME_SIZE); dev_set_name(&rtc->dev, "rtc%d", id); diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c index cb2f072..8ec6b06 100644 --- a/drivers/rtc/interface.c +++ b/drivers/rtc/interface.c @@ -116,6 +116,186 @@ int rtc_set_mmss(struct rtc_device *rtc, unsigned long secs) } EXPORT_SYMBOL_GPL(rtc_set_mmss); +static int rtc_read_alarm_internal(struct rtc_device *rtc, struct rtc_wkalrm *alarm) +{ + int err; + + err = mutex_lock_interruptible(&rtc->ops_lock); + if (err) + return err; + + if (rtc->ops == NULL) + err = -ENODEV; + else if (!rtc->ops->read_alarm) + err = -EINVAL; + else { + memset(alarm, 0, sizeof(struct rtc_wkalrm)); + err = rtc->ops->read_alarm(rtc->dev.parent, alarm); + } + + mutex_unlock(&rtc->ops_lock); + return err; +} + +int __rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm) +{ + int err; + struct rtc_time before, now; + int first_time = 1; + unsigned long t_now, t_alm; + enum { none, day, month, year } missing = none; + unsigned days; + + /* The lower level RTC driver may return -1 in some fields, + * creating invalid alarm->time values, for reasons like: + * + * - The hardware may not be capable of filling them in; + * many alarms match only on time-of-day fields, not + * day/month/year calendar data. + * + * - Some hardware uses illegal values as "wildcard" match + * values, which non-Linux firmware (like a BIOS) may try + * to set up as e.g. "alarm 15 minutes after each hour". + * Linux uses only oneshot alarms. + * + * When we see that here, we deal with it by using values from + * a current RTC timestamp for any missing (-1) values. The + * RTC driver prevents "periodic alarm" modes. + * + * But this can be racey, because some fields of the RTC timestamp + * may have wrapped in the interval since we read the RTC alarm, + * which would lead to us inserting inconsistent values in place + * of the -1 fields. + * + * Reading the alarm and timestamp in the reverse sequence + * would have the same race condition, and not solve the issue. + * + * So, we must first read the RTC timestamp, + * then read the RTC alarm value, + * and then read a second RTC timestamp. + * + * If any fields of the second timestamp have changed + * when compared with the first timestamp, then we know + * our timestamp may be inconsistent with that used by + * the low-level rtc_read_alarm_internal() function. + * + * So, when the two timestamps disagree, we just loop and do + * the process again to get a fully consistent set of values. + * + * This could all instead be done in the lower level driver, + * but since more than one lower level RTC implementation needs it, + * then it's probably best best to do it here instead of there.. + */ + + /* Get the "before" timestamp */ + err = rtc_read_time(rtc, &before); + if (err < 0) + return err; + do { + if (!first_time) + memcpy(&before, &now, sizeof(struct rtc_time)); + first_time = 0; + + /* get the RTC alarm values, which may be incomplete */ + err = rtc_read_alarm_internal(rtc, alarm); + if (err) + return err; + + /* full-function RTCs won't have such missing fields */ + if (rtc_valid_tm(&alarm->time) == 0) + return 0; + + /* get the "after" timestamp, to detect wrapped fields */ + err = rtc_read_time(rtc, &now); + if (err < 0) + return err; + + /* note that tm_sec is a "don't care" value here: */ + } while ( before.tm_min != now.tm_min + || before.tm_hour != now.tm_hour + || before.tm_mon != now.tm_mon + || before.tm_year != now.tm_year); + + /* Fill in the missing alarm fields using the timestamp; we + * know there's at least one since alarm->time is invalid. + */ + if (alarm->time.tm_sec == -1) + alarm->time.tm_sec = now.tm_sec; + if (alarm->time.tm_min == -1) + alarm->time.tm_min = now.tm_min; + if (alarm->time.tm_hour == -1) + alarm->time.tm_hour = now.tm_hour; + + /* For simplicity, only support date rollover for now */ + if (alarm->time.tm_mday == -1) { + alarm->time.tm_mday = now.tm_mday; + missing = day; + } + if (alarm->time.tm_mon == -1) { + alarm->time.tm_mon = now.tm_mon; + if (missing == none) + missing = month; + } + if (alarm->time.tm_year == -1) { + alarm->time.tm_year = now.tm_year; + if (missing == none) + missing = year; + } + + /* with luck, no rollover is needed */ + rtc_tm_to_time(&now, &t_now); + rtc_tm_to_time(&alarm->time, &t_alm); + if (t_now < t_alm) + goto done; + + switch (missing) { + + /* 24 hour rollover ... if it's now 10am Monday, an alarm that + * that will trigger at 5am will do so at 5am Tuesday, which + * could also be in the next month or year. This is a common + * case, especially for PCs. + */ + case day: + dev_dbg(&rtc->dev, "alarm rollover: %s\n", "day"); + t_alm += 24 * 60 * 60; + rtc_time_to_tm(t_alm, &alarm->time); + break; + + /* Month rollover ... if it's the 31th, an alarm on the 3rd will + * be next month. An alarm matching on the 30th, 29th, or 28th + * may end up in the month after that! Many newer PCs support + * this type of alarm. + */ + case month: + dev_dbg(&rtc->dev, "alarm rollover: %s\n", "month"); + do { + if (alarm->time.tm_mon < 11) + alarm->time.tm_mon++; + else { + alarm->time.tm_mon = 0; + alarm->time.tm_year++; + } + days = rtc_month_days(alarm->time.tm_mon, + alarm->time.tm_year); + } while (days < alarm->time.tm_mday); + break; + + /* Year rollover ... easy except for leap years! */ + case year: + dev_dbg(&rtc->dev, "alarm rollover: %s\n", "year"); + do { + alarm->time.tm_year++; + } while (rtc_valid_tm(&alarm->time) != 0); + break; + + default: + dev_warn(&rtc->dev, "alarm rollover not handled\n"); + } + +done: + return 0; +} + int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm) { int err; diff --git a/include/linux/rtc.h b/include/linux/rtc.h index 89c3e51..db3832d 100644 --- a/include/linux/rtc.h +++ b/include/linux/rtc.h @@ -227,6 +227,7 @@ extern void rtc_device_unregister(struct rtc_device *rtc); extern int rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm); extern int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm); extern int rtc_set_mmss(struct rtc_device *rtc, unsigned long secs); +int __rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alarm); extern int rtc_read_alarm(struct rtc_device *rtc, struct rtc_wkalrm *alrm); extern int rtc_set_alarm(struct rtc_device *rtc,