[PATCH] RTC framework driver for CMOS RTCs

This is an "RTC framework" driver for the "CMOS" RTCs which are standard on
PCs and some other platforms.  That's MC146818 compatible silicon.
Advantages of this vs.  drivers/char/rtc.c (use one _or_ the other, only
one will be able to claim the RTC irq) include:

 - This leverages both the new RTC framework and the driver model; both
   PNPACPI and platform device modes are supported.  (A separate patch
   creates a platform device on PCs where PNPACPI isn't configured.)

 - It supports common extensions like longer alarms.  (A separate patch
   exports that information from ACPI through platform_data.)

 - Likewise, system wakeup events use "real driver model support", with
   policy control via sysfs "wakeup" attributes and and using normal rtc
   ioctls to manage wakeup.  (Patch in the works.  The ACPI hooks are
   known; /proc/acpi/alarm can vanish.  Making it work with EFI will
   be a minor challenge to someone with e.g. a MiniMac.)

It's not yet been tested on non-x86 systems, without ACPI, or with HPET.
And the RTC framework will surely have teething pains on "mainstream"
PC-based systems (though must embedded Linux systems use it heavily), not
limited to sorting out the "/dev/rtc0" issue (udev easily tweaked).  Also,
the ALSA rtctimer code doesn't use the new RTC API.

Otherwise, this should be a no-known-regressions replacement for the old
drivers/char/rtc.c driver, and should help the non-embedded distros (and
the new timekeeping code) start to switch to the framework.

Note also that any systems using "rtc-m48t86" are candidates to switch over
to this more functional driver; the platform data is different, and the way
bytes are read is different, but otherwise those chips should be compatible.

[akpm@osdl.org: sparc32 fix]
[akpm@osdl.org: sparc64 fix]
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Woody Suwalski <woodys@xandros.com>
Cc: Alessandro Zummo <alessandro.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 750 insertions, 1 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 09660e2ab05..4bbca500d3d 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -1,4 +1,4 @@
-\#
+#
 # RTC class/drivers configuration
 #
 
@@ -95,6 +95,29 @@ config RTC_INTF_DEV_UIE_EMUL
 comment "RTC drivers"
 	depends on RTC_CLASS
 
+# this 'CMOS' RTC driver is arch dependent because <asm-generic/rtc.h>
+# requires <asm/mc146818rtc.h> defining CMOS_READ/CMOS_WRITE, and a
+# global rtc_lock ... it's not yet just another platform_device.
+
+config RTC_DRV_CMOS
+	tristate "PC-style 'CMOS' real time clock"
+	depends on RTC_CLASS && (X86_PC || ALPHA || ARM26 || ARM \
+		|| M32R || ATARI || POWERPC)
+	help
+	  Say "yes" here to get direct support for the real time clock
+	  found in every PC or ACPI-based system, and some other boards.
+	  Specifically the original MC146818, compatibles like those in
+	  PC south bridges, the DS12887 or M48T86, some multifunction
+	  or LPC bus chips, and so on.
+
+	  Your system will need to define the platform device used by
+	  this driver, otherwise it won't be accessible.  This means
+	  you can safely enable this driver if you don't know whether
+	  or not your board has this kind of hardware.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-cmos.
+
 config RTC_DRV_X1205
 	tristate "Xicor/Intersil X1205"
 	depends on RTC_CLASS && I2C
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index e6beedacc96..92bfe1b3a5f 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -15,6 +15,7 @@ obj-$(CONFIG_RTC_INTF_SYSFS)	+= rtc-sysfs.o
 obj-$(CONFIG_RTC_INTF_PROC)	+= rtc-proc.o
 obj-$(CONFIG_RTC_INTF_DEV)	+= rtc-dev.o
 
+obj-$(CONFIG_RTC_DRV_CMOS)	+= rtc-cmos.o
 obj-$(CONFIG_RTC_DRV_X1205)	+= rtc-x1205.o
 obj-$(CONFIG_RTC_DRV_ISL1208)	+= rtc-isl1208.o
 obj-$(CONFIG_RTC_DRV_TEST)	+= rtc-test.o
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
new file mode 100644
index 00000000000..85bf795abdc
--- /dev/null
+++ b/drivers/rtc/rtc-cmos.c
@@ -0,0 +1,725 @@
+/*
+ * RTC class driver for "CMOS RTC":  PCs, ACPI, etc
+ *
+ * Copyright (C) 1996 Paul Gortmaker (drivers/char/rtc.c)
+ * Copyright (C) 2006 David Brownell (convert to new framework)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+/*
+ * The original "cmos clock" chip was an MC146818 chip, now obsolete.
+ * That defined the register interface now provided by all PCs, some
+ * non-PC systems, and incorporated into ACPI.  Modern PC chipsets
+ * integrate an MC146818 clone in their southbridge, and boards use
+ * that instead of discrete clones like the DS12887 or M48T86.  There
+ * are also clones that connect using the LPC bus.
+ *
+ * That register API is also used directly by various other drivers
+ * (notably for integrated NVRAM), infrastructure (x86 has code to
+ * bypass the RTC framework, directly reading the RTC during boot
+ * and updating minutes/seconds for systems using NTP synch) and
+ * utilities (like userspace 'hwclock', if no /dev node exists).
+ *
+ * So **ALL** calls to CMOS_READ and CMOS_WRITE must be done with
+ * interrupts disabled, holding the global rtc_lock, to exclude those
+ * other drivers and utilities on correctly configured systems.
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/platform_device.h>
+#include <linux/mod_devicetable.h>
+
+/* this is for "generic access to PC-style RTC" using CMOS_READ/CMOS_WRITE */
+#include <asm-generic/rtc.h>
+
+
+struct cmos_rtc {
+	struct rtc_device	*rtc;
+	struct device		*dev;
+	int			irq;
+	struct resource		*iomem;
+
+	u8			suspend_ctrl;
+
+	/* newer hardware extends the original register set */
+	u8			day_alrm;
+	u8			mon_alrm;
+	u8			century;
+};
+
+/* both platform and pnp busses use negative numbers for invalid irqs */
+#define is_valid_irq(n)		((n) >= 0)
+
+static const char driver_name[] = "rtc_cmos";
+
+/*----------------------------------------------------------------*/
+
+static int cmos_read_time(struct device *dev, struct rtc_time *t)
+{
+	/* REVISIT:  if the clock has a "century" register, use
+	 * that instead of the heuristic in get_rtc_time().
+	 * That'll make Y3K compatility (year > 2070) easy!
+	 */
+	get_rtc_time(t);
+	return 0;
+}
+
+static int cmos_set_time(struct device *dev, struct rtc_time *t)
+{
+	/* REVISIT:  set the "century" register if available
+	 *
+	 * NOTE: this ignores the issue whereby updating the seconds
+	 * takes effect exactly 500ms after we write the register.
+	 * (Also queueing and other delays before we get this far.)
+	 */
+	return set_rtc_time(t);
+}
+
+static int cmos_read_alarm(struct device *dev, struct rtc_wkalrm *t)
+{
+	struct cmos_rtc	*cmos = dev_get_drvdata(dev);
+	unsigned char	rtc_control;
+
+	if (!is_valid_irq(cmos->irq))
+		return -EIO;
+
+	/* Basic alarms only support hour, minute, and seconds fields.
+	 * Some also support day and month, for alarms up to a year in
+	 * the future.
+	 */
+	t->time.tm_mday = -1;
+	t->time.tm_mon = -1;
+
+	spin_lock_irq(&rtc_lock);
+	t->time.tm_sec = CMOS_READ(RTC_SECONDS_ALARM);
+	t->time.tm_min = CMOS_READ(RTC_MINUTES_ALARM);
+	t->time.tm_hour = CMOS_READ(RTC_HOURS_ALARM);
+
+	if (cmos->day_alrm) {
+		t->time.tm_mday = CMOS_READ(cmos->day_alrm);
+		if (!t->time.tm_mday)
+			t->time.tm_mday = -1;
+
+		if (cmos->mon_alrm) {
+			t->time.tm_mon = CMOS_READ(cmos->mon_alrm);
+			if (!t->time.tm_mon)
+				t->time.tm_mon = -1;
+		}
+	}
+
+	rtc_control = CMOS_READ(RTC_CONTROL);
+	spin_unlock_irq(&rtc_lock);
+
+	/* REVISIT this assumes PC style usage:  always BCD */
+
+	if (((unsigned)t->time.tm_sec) < 0x60)
+		t->time.tm_sec = BCD2BIN(t->time.tm_sec);
+	else
+		t->time.tm_sec = -1;
+	if (((unsigned)t->time.tm_min) < 0x60)
+		t->time.tm_min = BCD2BIN(t->time.tm_min);
+	else
+		t->time.tm_min = -1;
+	if (((unsigned)t->time.tm_hour) < 0x24)
+		t->time.tm_hour = BCD2BIN(t->time.tm_hour);
+	else
+		t->time.tm_hour = -1;
+
+	if (cmos->day_alrm) {
+		if (((unsigned)t->time.tm_mday) <= 0x31)
+			t->time.tm_mday = BCD2BIN(t->time.tm_mday);
+		else
+			t->time.tm_mday = -1;
+		if (cmos->mon_alrm) {
+			if (((unsigned)t->time.tm_mon) <= 0x12)
+				t->time.tm_mon = BCD2BIN(t->time.tm_mon) - 1;
+			else
+				t->time.tm_mon = -1;
+		}
+	}
+	t->time.tm_year = -1;
+
+	t->enabled = !!(rtc_control & RTC_AIE);
+	t->pending = 0;
+
+	return 0;
+}
+
+static int cmos_set_alarm(struct device *dev, struct rtc_wkalrm *t)
+{
+	struct cmos_rtc	*cmos = dev_get_drvdata(dev);
+	unsigned char	mon, mday, hrs, min, sec;
+	unsigned char	rtc_control, rtc_intr;
+
+	if (!is_valid_irq(cmos->irq))
+		return -EIO;
+
+	/* REVISIT this assumes PC style usage:  always BCD */
+
+	/* Writing 0xff means "don't care" or "match all".  */
+
+	mon = t->time.tm_mon;
+	mon = (mon < 12) ? BIN2BCD(mon) : 0xff;
+	mon++;
+
+	mday = t->time.tm_mday;
+	mday = (mday >= 1 && mday <= 31) ? BIN2BCD(mday) : 0xff;
+
+	hrs = t->time.tm_hour;
+	hrs = (hrs < 24) ? BIN2BCD(hrs) : 0xff;
+
+	min = t->time.tm_min;
+	min = (min < 60) ? BIN2BCD(min) : 0xff;
+
+	sec = t->time.tm_sec;
+	sec = (sec < 60) ? BIN2BCD(sec) : 0xff;
+
+	spin_lock_irq(&rtc_lock);
+
+	/* next rtc irq must not be from previous alarm setting */
+	rtc_control = CMOS_READ(RTC_CONTROL);
+	rtc_control &= ~RTC_AIE;
+	CMOS_WRITE(rtc_control, RTC_CONTROL);
+	rtc_intr = CMOS_READ(RTC_INTR_FLAGS);
+	if (rtc_intr)
+		rtc_update_irq(&cmos->rtc->class_dev, 1, rtc_intr);
+
+	/* update alarm */
+	CMOS_WRITE(hrs, RTC_HOURS_ALARM);
+	CMOS_WRITE(min, RTC_MINUTES_ALARM);
+	CMOS_WRITE(sec, RTC_SECONDS_ALARM);
+
+	/* the system may support an "enhanced" alarm */
+	if (cmos->day_alrm) {
+		CMOS_WRITE(mday, cmos->day_alrm);
+		if (cmos->mon_alrm)
+			CMOS_WRITE(mon, cmos->mon_alrm);
+	}
+
+	if (t->enabled) {
+		rtc_control |= RTC_AIE;
+		CMOS_WRITE(rtc_control, RTC_CONTROL);
+		rtc_intr = CMOS_READ(RTC_INTR_FLAGS);
+		if (rtc_intr)
+			rtc_update_irq(&cmos->rtc->class_dev, 1, rtc_intr);
+	}
+
+	spin_unlock_irq(&rtc_lock);
+
+	return 0;
+}
+
+static int cmos_set_freq(struct device *dev, int freq)
+{
+	struct cmos_rtc	*cmos = dev_get_drvdata(dev);
+	int		f;
+	unsigned long	flags;
+
+	if (!is_valid_irq(cmos->irq))
+		return -ENXIO;
+
+	/* 0 = no irqs; 1 = 2^15 Hz ... 15 = 2^0 Hz */
+	f = ffs(freq);
+	if (f != 0) {
+		if (f-- > 16 || freq != (1 << f))
+			return -EINVAL;
+		f = 16 - f;
+	}
+
+	spin_lock_irqsave(&rtc_lock, flags);
+	CMOS_WRITE(RTC_REF_CLCK_32KHZ | f, RTC_FREQ_SELECT);
+	spin_unlock_irqrestore(&rtc_lock, flags);
+
+	return 0;
+}
+
+#if defined(CONFIG_RTC_INTF_DEV) || defined(CONFIG_RTC_INTF_DEV_MODULE)
+
+static int
+cmos_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
+{
+	struct cmos_rtc	*cmos = dev_get_drvdata(dev);
+	unsigned char	rtc_control, rtc_intr;
+	unsigned long	flags;
+
+	switch (cmd) {
+	case RTC_AIE_OFF:
+	case RTC_AIE_ON:
+	case RTC_UIE_OFF:
+	case RTC_UIE_ON:
+	case RTC_PIE_OFF:
+	case RTC_PIE_ON:
+		if (!is_valid_irq(cmos->irq))
+			return -EINVAL;
+		break;
+	default:
+		return -ENOIOCTLCMD;
+	}
+
+	spin_lock_irqsave(&rtc_lock, flags);
+	rtc_control = CMOS_READ(RTC_CONTROL);
+	switch (cmd) {
+	case RTC_AIE_OFF:	/* alarm off */
+		rtc_control &= ~RTC_AIE;
+		break;
+	case RTC_AIE_ON:	/* alarm on */
+		rtc_control |= RTC_AIE;
+		break;
+	case RTC_UIE_OFF:	/* update off */
+		rtc_control &= ~RTC_UIE;
+		break;
+	case RTC_UIE_ON:	/* update on */
+		rtc_control |= RTC_UIE;
+		break;
+	case RTC_PIE_OFF:	/* periodic off */
+		rtc_control &= ~RTC_PIE;
+		break;
+	case RTC_PIE_ON:	/* periodic on */
+		rtc_control |= RTC_PIE;
+		break;
+	}
+	CMOS_WRITE(rtc_control, RTC_CONTROL);
+	rtc_intr = CMOS_READ(RTC_INTR_FLAGS);
+	if (rtc_intr)
+		rtc_update_irq(&cmos->rtc->class_dev, 1, rtc_intr);
+	spin_unlock_irqrestore(&rtc_lock, flags);
+	return 0;
+}
+
+#else
+#define	cmos_rtc_ioctl	NULL
+#endif
+
+#if defined(CONFIG_RTC_INTF_PROC) || defined(CONFIG_RTC_INTF_PROC_MODULE)
+
+static int cmos_procfs(struct device *dev, struct seq_file *seq)
+{
+	struct cmos_rtc	*cmos = dev_get_drvdata(dev);
+	unsigned char	rtc_control, valid;
+
+	spin_lock_irq(&rtc_lock);
+	rtc_control = CMOS_READ(RTC_CONTROL);
+	valid = CMOS_READ(RTC_VALID);
+	spin_unlock_irq(&rtc_lock);
+
+	/* NOTE:  at least ICH6 reports battery status using a different
+	 * (non-RTC) bit; and SQWE is ignored on many current systems.
+	 */
+	return seq_printf(seq,
+			"periodic_IRQ\t: %s\n"
+			"update_IRQ\t: %s\n"
+			// "square_wave\t: %s\n"
+			// "BCD\t\t: %s\n"
+			"DST_enable\t: %s\n"
+			"periodic_freq\t: %d\n"
+			"batt_status\t: %s\n",
+			(rtc_control & RTC_PIE) ? "yes" : "no",
+			(rtc_control & RTC_UIE) ? "yes" : "no",
+			// (rtc_control & RTC_SQWE) ? "yes" : "no",
+			// (rtc_control & RTC_DM_BINARY) ? "no" : "yes",
+			(rtc_control & RTC_DST_EN) ? "yes" : "no",
+			cmos->rtc->irq_freq,
+			(valid & RTC_VRT) ? "okay" : "dead");
+}
+
+#else
+#define	cmos_procfs	NULL
+#endif
+
+static const struct rtc_class_ops cmos_rtc_ops = {
+	.ioctl		= cmos_rtc_ioctl,
+	.read_time	= cmos_read_time,
+	.set_time	= cmos_set_time,
+	.read_alarm	= cmos_read_alarm,
+	.set_alarm	= cmos_set_alarm,
+	.proc		= cmos_procfs,
+	.irq_set_freq	= cmos_set_freq,
+};
+
+/*----------------------------------------------------------------*/
+
+static struct cmos_rtc	cmos_rtc;
+
+static irqreturn_t cmos_interrupt(int irq, void *p)
+{
+	u8		irqstat;
+
+	spin_lock(&rtc_lock);
+	irqstat = CMOS_READ(RTC_INTR_FLAGS);
+	spin_unlock(&rtc_lock);
+
+	if (irqstat) {
+		/* NOTE: irqstat may have e.g. RTC_PF set
+		 * even when RTC_PIE is clear...
+		 */
+		rtc_update_irq(p, 1, irqstat);
+		return IRQ_HANDLED;
+	} else
+		return IRQ_NONE;
+}
+
+#ifdef	CONFIG_PNPACPI
+#define	is_pnpacpi()	1
+#define	INITSECTION
+
+#else
+#define	is_pnpacpi()	0
+#define	INITSECTION	__init
+#endif
+
+static int INITSECTION
+cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
+{
+	struct cmos_rtc_board_info	*info = dev->platform_data;
+	int				retval = 0;
+	unsigned char			rtc_control;
+
+	/* there can be only one ... */
+	if (cmos_rtc.dev)
+		return -EBUSY;
+
+	if (!ports)
+		return -ENODEV;
+
+	cmos_rtc.irq = rtc_irq;
+	cmos_rtc.iomem = ports;
+
+	/* For ACPI systems the info comes from the FADT.  On others,
+	 * board specific setup provides it as appropriate.
+	 */
+	if (info) {
+		cmos_rtc.day_alrm = info->rtc_day_alarm;
+		cmos_rtc.mon_alrm = info->rtc_mon_alarm;
+		cmos_rtc.century = info->rtc_century;
+	}
+
+	cmos_rtc.rtc = rtc_device_register(driver_name, dev,
+				&cmos_rtc_ops, THIS_MODULE);
+	if (IS_ERR(cmos_rtc.rtc))
+		return PTR_ERR(cmos_rtc.rtc);
+
+	cmos_rtc.dev = dev;
+	dev_set_drvdata(dev, &cmos_rtc);
+
+	/* platform and pnp busses handle resources incompatibly.
+	 *
+	 * REVISIT for non-x86 systems we may need to handle io memory
+	 * resources: ioremap them, and request_mem_region().
+	 */
+	if (is_pnpacpi()) {
+		retval = request_resource(&ioport_resource, ports);
+		if (retval < 0) {
+			dev_dbg(dev, "i/o registers already in use\n");
+			goto cleanup0;
+		}
+	}
+	rename_region(ports, cmos_rtc.rtc->class_dev.class_id);
+
+	spin_lock_irq(&rtc_lock);
+
+	/* force periodic irq to CMOS reset default of 1024Hz;
+	 *
+	 * REVISIT it's been reported that at least one x86_64 ALI mobo
+	 * doesn't use 32KHz here ... for portability we might need to
+	 * do something about other clock frequencies.
+	 */
+	CMOS_WRITE(RTC_REF_CLCK_32KHZ | 0x06, RTC_FREQ_SELECT);
+	cmos_rtc.rtc->irq_freq = 1024;
+
+	/* disable irqs.
+	 *
+	 * NOTE after changing RTC_xIE bits we always read INTR_FLAGS;
+	 * allegedly some older rtcs need that to handle irqs properly
+	 */
+	rtc_control = CMOS_READ(RTC_CONTROL);
+	rtc_control &= ~(RTC_PIE | RTC_AIE | RTC_UIE);
+	CMOS_WRITE(rtc_control, RTC_CONTROL);
+	CMOS_READ(RTC_INTR_FLAGS);
+
+	spin_unlock_irq(&rtc_lock);
+
+	/* FIXME teach the alarm code how to handle binary mode;
+	 * <asm-generic/rtc.h> doesn't know 12-hour mode either.
+	 */
+	if (!(rtc_control & RTC_24H) || (rtc_control & (RTC_DM_BINARY))) {
+		dev_dbg(dev, "only 24-hr BCD mode supported\n");
+		retval = -ENXIO;
+		goto cleanup1;
+	}
+
+	if (is_valid_irq(rtc_irq))
+		retval = request_irq(rtc_irq, cmos_interrupt, IRQF_DISABLED,
+				cmos_rtc.rtc->class_dev.class_id,
+				&cmos_rtc.rtc->class_dev);
+	if (retval < 0) {
+		dev_dbg(dev, "IRQ %d is already in use\n", rtc_irq);
+		goto cleanup1;
+	}
+
+	/* REVISIT optionally make 50 or 114 bytes NVRAM available,
+	 * like rtc-ds1553, rtc-ds1742 ... this will often include
+	 * registers for century, and day/month alarm.
+	 */
+
+	pr_info("%s: alarms up to one %s%s\n",
+			cmos_rtc.rtc->class_dev.class_id,
+			is_valid_irq(rtc_irq)
+				?  (cmos_rtc.mon_alrm
+					? "year"
+					: (cmos_rtc.day_alrm
+						? "month" : "day"))
+				: "no",
+			cmos_rtc.century ? ", y3k" : ""
+			);
+
+	return 0;
+
+cleanup1:
+	rename_region(ports, NULL);
+cleanup0:
+	rtc_device_unregister(cmos_rtc.rtc);
+	return retval;
+}
+
+static void cmos_do_shutdown(void)
+{
+	unsigned char	rtc_control;
+
+	spin_lock_irq(&rtc_lock);
+	rtc_control = CMOS_READ(RTC_CONTROL);
+	rtc_control &= ~(RTC_PIE|RTC_AIE|RTC_UIE);
+	CMOS_WRITE(rtc_control, RTC_CONTROL);
+	CMOS_READ(RTC_INTR_FLAGS);
+	spin_unlock_irq(&rtc_lock);
+}
+
+static void __exit cmos_do_remove(struct device *dev)
+{
+	struct cmos_rtc	*cmos = dev_get_drvdata(dev);
+
+	cmos_do_shutdown();
+
+	if (is_pnpacpi())
+		release_resource(cmos->iomem);
+	rename_region(cmos->iomem, NULL);
+
+	if (is_valid_irq(cmos->irq))
+		free_irq(cmos->irq, &cmos_rtc.rtc->class_dev);
+
+	rtc_device_unregister(cmos_rtc.rtc);
+
+	cmos_rtc.dev = NULL;
+	dev_set_drvdata(dev, NULL);
+}
+
+#ifdef	CONFIG_PM
+
+static int cmos_suspend(struct device *dev, pm_message_t mesg)
+{
+	struct cmos_rtc	*cmos = dev_get_drvdata(dev);
+	int		do_wake = device_may_wakeup(dev);
+	unsigned char	tmp, irqstat;
+
+	/* only the alarm might be a wakeup event source */
+	spin_lock_irq(&rtc_lock);
+	cmos->suspend_ctrl = tmp = CMOS_READ(RTC_CONTROL);
+	if (tmp & (RTC_PIE|RTC_AIE|RTC_UIE)) {
+		if (do_wake)
+			tmp &= ~(RTC_PIE|RTC_UIE);
+		else
+			tmp &= ~(RTC_PIE|RTC_AIE|RTC_UIE);
+		CMOS_WRITE(tmp, RTC_CONTROL);
+		irqstat = CMOS_READ(RTC_INTR_FLAGS);
+	} else
+		irqstat = 0;
+	spin_unlock_irq(&rtc_lock);
+
+	if (irqstat)
+		rtc_update_irq(&cmos->rtc->class_dev, 1, irqstat);
+
+	/* ACPI HOOK:  enable ACPI_EVENT_RTC when (tmp & RTC_AIE)
+	 * ... it'd be best if we could do that under rtc_lock.
+	 */
+
+	pr_debug("%s: suspend%s, ctrl %02x\n",
+			cmos_rtc.rtc->class_dev.class_id,
+			(tmp & RTC_AIE) ? ", alarm may wake" : "",
+			tmp);
+
+	return 0;
+}
+
+static int cmos_resume(struct device *dev)
+{
+	struct cmos_rtc	*cmos = dev_get_drvdata(dev);
+	unsigned char	tmp = cmos->suspend_ctrl;
+
+	/* REVISIT:  a mechanism to resync the system clock (jiffies)
+	 * on resume should be portable between platforms ...
+	 */
+
+	/* re-enable any irqs previously active */
+	if (tmp & (RTC_PIE|RTC_AIE|RTC_UIE)) {
+
+		/* ACPI HOOK:  disable ACPI_EVENT_RTC when (tmp & RTC_AIE) */
+
+		spin_lock_irq(&rtc_lock);
+		CMOS_WRITE(tmp, RTC_CONTROL);
+		tmp = CMOS_READ(RTC_INTR_FLAGS);
+		spin_unlock_irq(&rtc_lock);
+		if (tmp)
+			rtc_update_irq(&cmos->rtc->class_dev, 1, tmp);
+	}
+
+	pr_debug("%s: resume, ctrl %02x\n",
+			cmos_rtc.rtc->class_dev.class_id,
+			cmos->suspend_ctrl);
+
+
+	return 0;
+}
+
+#else
+#define	cmos_suspend	NULL
+#define	cmos_resume	NULL
+#endif
+
+/*----------------------------------------------------------------*/
+
+/* The "CMOS" RTC normally lives on the platform_bus.  On ACPI systems,
+ * the device node may alternatively be created as a PNP device.
+ */
+
+#ifdef	CONFIG_PNPACPI
+
+#include <linux/pnp.h>
+
+static int __devinit
+cmos_pnp_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
+{
+	/* REVISIT paranoia argues for a shutdown notifier, since PNP
+	 * drivers can't provide shutdown() methods to disable IRQs.
+	 * Or better yet, fix PNP to allow those methods...
+	 */
+	return cmos_do_probe(&pnp->dev,
+			&pnp->res.port_resource[0],
+			pnp->res.irq_resource[0].start);
+}
+
+static void __exit cmos_pnp_remove(struct pnp_dev *pnp)
+{
+	cmos_do_remove(&pnp->dev);
+}
+
+#ifdef	CONFIG_PM
+
+static int cmos_pnp_suspend(struct pnp_dev *pnp, pm_message_t mesg)
+{
+	return cmos_suspend(&pnp->dev, mesg);
+}
+
+static int cmos_pnp_resume(struct pnp_dev *pnp)
+{
+	return cmos_resume(&pnp->dev);
+}
+
+#else
+#define	cmos_pnp_suspend	NULL
+#define	cmos_pnp_resume		NULL
+#endif
+
+
+static const struct pnp_device_id rtc_ids[] = {
+	{ .id = "PNP0b00", },
+	{ .id = "PNP0b01", },
+	{ .id = "PNP0b02", },
+	{ },
+};
+MODULE_DEVICE_TABLE(pnp, rtc_ids);
+
+static struct pnp_driver cmos_pnp_driver = {
+	.name		= (char *) driver_name,
+	.id_table	= rtc_ids,
+	.probe		= cmos_pnp_probe,
+	.remove		= __exit_p(cmos_pnp_remove),
+
+	/* flag ensures resume() gets called, and stops syslog spam */
+	.flags		= PNP_DRIVER_RES_DO_NOT_CHANGE,
+	.suspend	= cmos_pnp_suspend,
+	.resume		= cmos_pnp_resume,
+};
+
+static int __init cmos_init(void)
+{
+	return pnp_register_driver(&cmos_pnp_driver);
+}
+module_init(cmos_init);
+
+static void __exit cmos_exit(void)
+{
+	pnp_unregister_driver(&cmos_pnp_driver);
+}
+module_exit(cmos_exit);
+
+#else	/* no PNPACPI */
+
+/*----------------------------------------------------------------*/
+
+/* Platform setup should have set up an RTC device, when PNPACPI is
+ * unavailable ... this is the normal case, common even on PCs.
+ */
+
+static int __init cmos_platform_probe(struct platform_device *pdev)
+{
+	return cmos_do_probe(&pdev->dev,
+			platform_get_resource(pdev, IORESOURCE_IO, 0),
+			platform_get_irq(pdev, 0));
+}
+
+static int __exit cmos_platform_remove(struct platform_device *pdev)
+{
+	cmos_do_remove(&pdev->dev);
+	return 0;
+}
+
+static void cmos_platform_shutdown(struct platform_device *pdev)
+{
+	cmos_do_shutdown();
+}
+
+static struct platform_driver cmos_platform_driver = {
+	.remove		= __exit_p(cmos_platform_remove),
+	.shutdown	= cmos_platform_shutdown,
+	.driver = {
+		.name		= (char *) driver_name,
+		.suspend	= cmos_suspend,
+		.resume		= cmos_resume,
+	}
+};
+
+static int __init cmos_init(void)
+{
+	return platform_driver_probe(&cmos_platform_driver,
+			cmos_platform_probe);
+}
+module_init(cmos_init);
+
+static void __exit cmos_exit(void)
+{
+	platform_driver_unregister(&cmos_platform_driver);
+}
+module_exit(cmos_exit);
+
+
+#endif	/* !PNPACPI */
+
+MODULE_AUTHOR("David Brownell");
+MODULE_DESCRIPTION("Driver for PC-style 'CMOS' RTCs");
+MODULE_LICENSE("GPL");