[patch 2.6.20-rc3 1/3] rtc-cmos driver

[patch 2.6.20-rc3 1/3] rtc-cmos driver

[David Brownell]

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.

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

====
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.

 drivers/rtc/Kconfig         |   13 
 drivers/rtc/Makefile        |    1 
 drivers/rtc/rtc-cmos.c      |  718 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/mc146818rtc.h |   10 
 4 files changed, 742 insertions(+)

Index: g26/drivers/rtc/Kconfig
===================================================================
--- g26.orig/drivers/rtc/Kconfig	2006-12-27 18:21:01.000000000 -0800
+++ g26/drivers/rtc/Kconfig	2006-12-28 01:38:47.000000000 -0800
@@ -95,6 +95,19 @@ config RTC_INTF_DEV_UIE_EMUL
 comment "RTC drivers"
 	depends on RTC_CLASS
 
+config RTC_DRV_CMOS
+	tristate "CMOS real time clock"
+	depends on RTC_CLASS && (X86_PC || ACPI)
+	help
+	  Say "yes" here to get direct support for the real time clock
+	  found in every PC or ACPI-based system, and some others.
+	  Specifically the original MC146818, compatibles like those
+	  in PC south bridges, the DS12887 or M48T86, some LPC bus
+	  chips, and so on.
+
+	  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
Index: g26/drivers/rtc/Makefile
===================================================================
--- g26.orig/drivers/rtc/Makefile	2006-12-27 13:49:11.000000000 -0800
+++ g26/drivers/rtc/Makefile	2006-12-27 18:21:02.000000000 -0800
@@ -15,6 +15,7 @@ obj-$(CONFIG_RTC_INTF_SYSFS)	+= rtc-sysf
 obj-$(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
Index: g26/include/linux/mc146818rtc.h
===================================================================
--- g26.orig/include/linux/mc146818rtc.h	2006-12-27 13:49:11.000000000 -0800
+++ g26/include/linux/mc146818rtc.h	2006-12-28 01:21:20.000000000 -0800
@@ -18,6 +18,16 @@
 #ifdef __KERNEL__
 #include <linux/spinlock.h>		/* spinlock_t */
 extern spinlock_t rtc_lock;		/* serialize CMOS RAM access */
+
+/* Some RTCs extend the mc146818 register set to support alarms of more
+ * than 24 hours in the future; or dates that include a century code.
+ * This platform_data structure can pass this information to the driver.
+ */
+struct cmos_rtc_board_info {
+	u8	rtc_day_alarm;		/* zero, or register index */
+	u8	rtc_mon_alarm;		/* zero, or register index */
+	u8	rtc_century;		/* zero, or register index */
+};
 #endif
 
 /**********************************************************************
Index: g26/drivers/rtc/rtc-cmos.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ g26/drivers/rtc/rtc-cmos.c	2006-12-28 01:30:33.000000000 -0800
@@ -0,0 +1,718 @@
+/*
+ * 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>
+
+#include <asm/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);
+
+	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;
+
+	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
+
+/*----------------------------------------------------------------*/
+
+/* On ACPI systems, the device node may be created as either a PNP
+ * device or a platform_device.  In either case the FADT data should
+ * have been transferred to us through platform_data.
+ */
+
+#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 ... including non-PC and non-ACPI platforms.
+ */
+
+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_DESCRIPTION("'CMOS' RTC driver:  PCs, ACPI, etc");
+MODULE_LICENSE("GPL");

Re: [patch 2.6.20-rc3 1/3] rtc-cmos driver

[Alessandro Zummo]

On Fri, 5 Jan 2007 10:01:57 -0800
David Brownell <david-b@pacbell.net> wrote:

> 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:

 Hi David,

  good code and well commented, thank you.
 
 I only have some comments:

 - I would put anything that is x86 related (pnp,acpi)
 in a separate file so that people working on
 non x86 systems can have a better grasp of the driver.
 
 - the name should be rtc-mc146818 to be coherent with
 the other drivers, but this can cause confusion.

 - please put yourself in MODULE_AUTHOR

 other than that, I'm fine with the code.

 I'd appreciate if someone (Woody?) can test
 this code on ARM.

-- 

 Best regards,

 Alessandro Zummo,
  Tower Technologies - Torino, Italy

  http://www.towertech.it

Re: [patch 2.6.20-rc3 1/3] rtc-cmos driver

[David Brownell]

On Friday 05 January 2007 12:45 pm, Alessandro Zummo wrote:
> On Fri, 5 Jan 2007 10:01:57 -0800
> David Brownell <david-b@pacbell.net> wrote:
> 
> > 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:
> 
>  Hi David,
> 
>   good code and well commented, thank you.

Glad to hear it!
  
>  I only have some comments:
>
>  - I would put anything that is x86 related (pnp,acpi)
>  in a separate file so that people working on
>  non x86 systems can have a better grasp of the driver.

I believe that splitting this driver into multiple files
would create more confusion confusion than it solves.  Bus
glue is actually a very small part of the code, and it's
cleanly split out.  So I'm not keen on this change at all.

And having done a grep of the source tree, splitting out PNP
bus glue (and platform bus glue?) into a separate file isn't
common.  IDE does, and 8250; both cases with a *very* complex
core, shared with many drivers.  But the normal case #ifdefs
PNP support, combining it with alternative bus glue which is
all too often nasty legacy "probe the hardware" logic.

(Also:  there are no longer any ACPI calls in this driver; and
do recall that at least ia64 uses ACPI too.  So _none_ of that
code is x86-specific...)


>  - the name should be rtc-mc146818 to be coherent with
>  the other drivers, but this can cause confusion.

Yes, I used the "rtc-cmos" name to minimize confusion.  It's a
generic name; I've even seen multiple books, including some
southbridge docs, talking about "CMOS RTC" or "CMOS clock".

"MC146818" is easy to mistype, hard to say, obsolete (!), and
virtually unused in most technical contexts.  But "cmos clock"
is widely understood, at least in PC-derived contexts, and
make sense talking about most any southbridge.

I guess I'm surprised you called rtc-m48t86 that, instead of
using the name rtc-mc146818 (since ST markets that M48 chip
as a replacement for the mc146818)... :)

I'm not deeply attached to this name, but I couldn't come up
with a better generic name.


>  - please put yourself in MODULE_AUTHOR

OK.  Appended.


>  other than that, I'm fine with the code.
> 
>  I'd appreciate if someone (Woody?) can test
>  this code on ARM.

There are PPC, M68K, SPARC, and other boards that could also
use this; ARMs tend to integrate some other RTC on-chip.  But
on whatever non-PC platform is involved in such sanity testing,
that involves adding a platform_device to board setup code.

- Dave

==============	CUT HERE
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.

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

---
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.

 drivers/rtc/Kconfig         |   13 
 drivers/rtc/Makefile        |    1 
 drivers/rtc/rtc-cmos.c      |  718 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/mc146818rtc.h |   10 
 4 files changed, 742 insertions(+)

Index: g26/drivers/rtc/Kconfig
===================================================================
--- g26.orig/drivers/rtc/Kconfig	2007-01-02 19:24:32.000000000 -0800
+++ g26/drivers/rtc/Kconfig	2007-01-02 23:35:41.000000000 -0800
@@ -95,6 +95,19 @@ config RTC_INTF_DEV_UIE_EMUL
 comment "RTC drivers"
 	depends on RTC_CLASS
 
+config RTC_DRV_CMOS
+	tristate "CMOS real time clock"
+	depends on RTC_CLASS && (X86_PC || ACPI)
+	help
+	  Say "yes" here to get direct support for the real time clock
+	  found in every PC or ACPI-based system, and some others.
+	  Specifically the original MC146818, compatibles like those
+	  in PC south bridges, the DS12887 or M48T86, some LPC bus
+	  chips, and so on.
+
+	  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
Index: g26/drivers/rtc/Makefile
===================================================================
--- g26.orig/drivers/rtc/Makefile	2007-01-02 19:24:29.000000000 -0800
+++ g26/drivers/rtc/Makefile	2007-01-02 23:35:41.000000000 -0800
@@ -15,6 +15,7 @@ obj-$(CONFIG_RTC_INTF_SYSFS)	+= rtc-sysf
 obj-$(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
Index: g26/include/linux/mc146818rtc.h
===================================================================
--- g26.orig/include/linux/mc146818rtc.h	2007-01-02 19:24:29.000000000 -0800
+++ g26/include/linux/mc146818rtc.h	2007-01-02 23:35:41.000000000 -0800
@@ -18,6 +18,16 @@
 #ifdef __KERNEL__
 #include <linux/spinlock.h>		/* spinlock_t */
 extern spinlock_t rtc_lock;		/* serialize CMOS RAM access */
+
+/* Some RTCs extend the mc146818 register set to support alarms of more
+ * than 24 hours in the future; or dates that include a century code.
+ * This platform_data structure can pass this information to the driver.
+ */
+struct cmos_rtc_board_info {
+	u8	rtc_day_alarm;		/* zero, or register index */
+	u8	rtc_mon_alarm;		/* zero, or register index */
+	u8	rtc_century;		/* zero, or register index */
+};
 #endif
 
 /**********************************************************************
Index: g26/drivers/rtc/rtc-cmos.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ g26/drivers/rtc/rtc-cmos.c	2007-01-05 18:17:21.000000000 -0800
@@ -0,0 +1,722 @@
+/*
+ * 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>
+
+#include <asm/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;
+
+	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
+
+/*----------------------------------------------------------------*/
+
+/* On ACPI systems, the device node may be created as either a PNP
+ * device or a platform_device.  In either case the FADT data should
+ * have been transferred to us through platform_data.
+ */
+
+#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 ... including non-PC and non-ACPI platforms.
+ */
+
+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("'CMOS' RTC driver:  PCs, ACPI, etc");
+MODULE_LICENSE("GPL");

Re: [patch 2.6.20-rc3 1/3] rtc-cmos driver

[David Brownell]

On Friday 05 January 2007 7:10 pm, David Brownell wrote:
> On Friday 05 January 2007 12:45 pm, Alessandro Zummo wrote:

> >  I'd appreciate if someone (Woody?) can test
> >  this code on ARM.
> 
> There are PPC, M68K, SPARC, and other boards that could also
> use this; ARMs tend to integrate some other RTC on-chip.  But
> on whatever non-PC platform is involved in such sanity testing,
> that involves adding a platform_device to board setup code.

Let me put that differently.  That should be done as a separate
patch, adding (a) that platform_device, and maybe platform_data
if it's got additional alarm registers, and (b) Kconfig support
to let that work.  I'd call it a "patch #4 of 3".  ;)

The current Kconfig uses:

> +config RTC_DRV_CMOS
> +       tristate "CMOS real time clock"
> +       depends on RTC_CLASS && (X86_PC || ACPI)

Eventually maybe the PC-or-ACPI stuff should vanish, but IMO
not until this code has been used on a few other platforms.

- Dave

Re: [patch 2.6.20-rc3 1/3] rtc-cmos driver

[Woody Suwalski]

David Brownell wrote:
> On Friday 05 January 2007 7:10 pm, David Brownell wrote:
>   
>> On Friday 05 January 2007 12:45 pm, Alessandro Zummo wrote:
>>     
>
>   
>>>  I'd appreciate if someone (Woody?) can test
>>>  this code on ARM.
>>>       
>> There are PPC, M68K, SPARC, and other boards that could also
>> use this; ARMs tend to integrate some other RTC on-chip.  But
>> on whatever non-PC platform is involved in such sanity testing,
>> that involves adding a platform_device to board setup code.
>>     
>
> Let me put that differently.  That should be done as a separate
> patch, adding (a) that platform_device, and maybe platform_data
> if it's got additional alarm registers, and (b) Kconfig support
> to let that work.  I'd call it a "patch #4 of 3".  ;)
>
> The current Kconfig uses:
>
>   
>> +config RTC_DRV_CMOS
>> +       tristate "CMOS real time clock"
>> +       depends on RTC_CLASS && (X86_PC || ACPI)
>>     
>
> Eventually maybe the PC-or-ACPI stuff should vanish, but IMO
> not until this code has been used on a few other platforms.
>
> - Dave
>   
I will try to play with the new code on Monday on ARM...

Thanks, Woody

Re: [patch 2.6.20-rc3 1/3] rtc-cmos driver

[David Brownell]

On Saturday 06 January 2007 9:17 am, Woody Suwalski wrote:
> >> There are PPC, M68K, SPARC, and other boards that could also
> >> use this; ARMs tend to integrate some other RTC on-chip.  ...
> 
> > Let me put that differently.  That should be done as a separate
> > patch, adding (a) that platform_device, and maybe platform_data
> > if it's got additional alarm registers, and (b) Kconfig support
> > to let that work.  I'd call it a "patch #4 of 3".  ;)
> > ...
> 
> I will try to play with the new code on Monday on ARM...

Thanks.  Could you describe your ARM board?  None of mine have an
RTC using this register API.  Does it support system sleep states
(/sys/power/state) with a wakeup-capable (enable_irq_wake) RTC irq? 

- Dave

Re: [patch 2.6.20-rc3 1/3] rtc-cmos driver

[Russell King]

On Sat, Jan 06, 2007 at 01:17:25PM -0800, David Brownell wrote:
> On Saturday 06 January 2007 9:17 am, Woody Suwalski wrote:
> > >> There are PPC, M68K, SPARC, and other boards that could also
> > >> use this; ARMs tend to integrate some other RTC on-chip.  ...
> > 
> > > Let me put that differently.  That should be done as a separate
> > > patch, adding (a) that platform_device, and maybe platform_data
> > > if it's got additional alarm registers, and (b) Kconfig support
> > > to let that work.  I'd call it a "patch #4 of 3".  ;)
> > > ...
> > 
> > I will try to play with the new code on Monday on ARM...
> 
> Thanks.  Could you describe your ARM board?  None of mine have an
> RTC using this register API.  Does it support system sleep states
> (/sys/power/state) with a wakeup-capable (enable_irq_wake) RTC irq? 

Woody will be using a Netwinder (he's part of the original development
team.)  So no sleep states and therefore no wakeup.

There's various other ARM-based systems using the PC RTC, but none of
them have sleep or wakeup abilities afaik.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:

Re: [patch 2.6.20-rc3 1/3] rtc-cmos driver

[Woody Suwalski]

[-- Attachment #1: Type: text/plain, Size: 2000 bytes --]

Russell King wrote:
> On Sat, Jan 06, 2007 at 01:17:25PM -0800, David Brownell wrote:
>   
>> On Saturday 06 January 2007 9:17 am, Woody Suwalski wrote:
>>     
>>>>> There are PPC, M68K, SPARC, and other boards that could also
>>>>> use this; ARMs tend to integrate some other RTC on-chip.  ...
>>>>>           
>>>> Let me put that differently.  That should be done as a separate
>>>> patch, adding (a) that platform_device, and maybe platform_data
>>>> if it's got additional alarm registers, and (b) Kconfig support
>>>> to let that work.  I'd call it a "patch #4 of 3".  ;)
>>>> ...
>>>>         
>>> I will try to play with the new code on Monday on ARM...
>>>       
>> Thanks.  Could you describe your ARM board?  None of mine have an
>> RTC using this register API.  Does it support system sleep states
>> (/sys/power/state) with a wakeup-capable (enable_irq_wake) RTC irq? 
>>     
>
> Woody will be using a Netwinder (he's part of the original development
> team.)  So no sleep states and therefore no wakeup.
>
> There's various other ARM-based systems using the PC RTC, but none of
> them have sleep or wakeup abilities afaik.
>
>   
I think that Russell is correct - the RTC is just part of a Winbond 
multifunction chip. It has no special wake-up or alarm hooks (as far as 
I remember).

As to the patch: applied to 2.6.20-rc4, both on PC and ARM, commented 
out "EXPERIMENTAL"...

To build your new patch for ARM I have modified the line "depends on 
RTC_CLASS && (X86_PC || ACPI || ARM)"...

On Netwinder ARM - can not build (see: rtc_build.log)

OK, changed the include/asm/rtc.h to look like i386 == include 
asm-generic/rtc.h
Still does not build - see rtc_build2.log

Could you please check what other defs are missing on ARM?

Thanks, Woody

BTW. Current RTC is broken same way on Shark ARM as it is on Netwinder ARM:

 >>>
<anderson@netsweng.com>
As for the RTC patch, it does work on the shark, and is needed.
<<<

So is there a reason to have RTC build blocked on all ARM?



[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: rtc_build.log --]
[-- Type: text/x-log; name="rtc_build.log", Size: 2828 bytes --]

  CHK     include/linux/version.h
make[1]: `include/asm-arm/mach-types.h' is up to date.
  CHK     include/linux/compile.h
  CHK     include/linux/utsrelease.h
  CC [M]  drivers/rtc/rtc-cmos.o
In file included from drivers/rtc/rtc-cmos.c:39:
include/asm/rtc.h:21: warning: 'struct rtc_time' declared inside parameter list
include/asm/rtc.h:21: warning: its scope is only this definition or declaration, which is probably not what you want
include/asm/rtc.h:22: warning: 'struct rtc_time' declared inside parameter list
include/asm/rtc.h:23: warning: 'struct rtc_wkalrm' declared inside parameter list
include/asm/rtc.h:24: warning: 'struct rtc_wkalrm' declared inside parameter list
include/asm/rtc.h:28: warning: 'struct rtc_time' declared inside parameter list
include/asm/rtc.h:33: warning: 'struct rtc_time' declared inside parameter list
include/asm/rtc.h: In function 'rtc_periodic_alarm':
include/asm/rtc.h:35: error: dereferencing pointer to incomplete type
include/asm/rtc.h:36: error: dereferencing pointer to incomplete type
include/asm/rtc.h:37: error: dereferencing pointer to incomplete type
include/asm/rtc.h:38: error: dereferencing pointer to incomplete type
include/asm/rtc.h:39: error: dereferencing pointer to incomplete type
include/asm/rtc.h:40: error: dereferencing pointer to incomplete type
drivers/rtc/rtc-cmos.c: At top level:
drivers/rtc/rtc-cmos.c:63: warning: 'struct rtc_time' declared inside parameter list
drivers/rtc/rtc-cmos.c: In function 'cmos_read_time':
drivers/rtc/rtc-cmos.c:69: warning: implicit declaration of function 'get_rtc_time'
drivers/rtc/rtc-cmos.c: At top level:
drivers/rtc/rtc-cmos.c:73: warning: 'struct rtc_time' declared inside parameter list
drivers/rtc/rtc-cmos.c: In function 'cmos_set_time':
drivers/rtc/rtc-cmos.c:81: warning: implicit declaration of function 'set_rtc_time'
drivers/rtc/rtc-cmos.c: At top level:
drivers/rtc/rtc-cmos.c:84: warning: 'struct rtc_wkalrm' declared inside parameter list
drivers/rtc/rtc-cmos.c: In function 'cmos_read_alarm':
drivers/rtc/rtc-cmos.c:96: error: dereferencing pointer to incomplete type
drivers/rtc/rtc-cmos.c:97: error: dereferencing pointer to incomplete type
drivers/rtc/rtc-cmos.c:99: error: 'rtc_lock' undeclared (first use in this function)
drivers/rtc/rtc-cmos.c:99: error: (Each undeclared identifier is reported only once
drivers/rtc/rtc-cmos.c:99: error: for each function it appears in.)
drivers/rtc/rtc-cmos.c:100: error: dereferencing pointer to incomplete type
drivers/rtc/rtc-cmos.c:100: warning: implicit declaration of function 'CMOS_READ'
drivers/rtc/rtc-cmos.c:100: error: 'RTC_SECONDS_ALARM' undeclared (first use in this function)
drivers/rtc/rtc-cmos.c:101: error: dereferencing pointer to incomplete type
drivers/rtc/rtc-cmos.c:101: error: 'RTC_MINUTES_ALARM' undeclared (first use in this function)

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #3: rtc_build2.log --]
[-- Type: text/x-log; name="rtc_build2.log", Size: 2178 bytes --]

  CHK     include/linux/version.h
make[1]: `include/asm-arm/mach-types.h' is up to date.
  CHK     include/linux/compile.h
  CHK     include/linux/utsrelease.h
  CC      arch/arm/common/rtctime.o
arch/arm/common/rtctime.c:34: error: static declaration of 'rtc_lock' follows non-static declaration
include/linux/mc146818rtc.h:20: error: previous declaration of 'rtc_lock' was here
arch/arm/common/rtctime.c: In function 'rtc_arm_read_time':
arch/arm/common/rtctime.c:76: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c: In function 'rtc_arm_set_time':
arch/arm/common/rtctime.c:85: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c: In function 'rtc_arm_read_alarm':
arch/arm/common/rtctime.c:93: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c:95: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c: In function 'rtc_arm_set_alarm':
arch/arm/common/rtctime.c:103: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c:104: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c: In function 'rtc_ioctl':
arch/arm/common/rtctime.c:276: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c:277: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c: In function 'rtc_open':
arch/arm/common/rtctime.c:291: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c:296: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c:296: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c: In function 'rtc_release':
arch/arm/common/rtctime.c:314: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c:315: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c:321: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c: In function 'rtc_read_proc':
arch/arm/common/rtctime.c:401: error: dereferencing pointer to incomplete type
arch/arm/common/rtctime.c:402: error: dereferencing pointer to incomplete type
make[1]: *** [arch/arm/common/rtctime.o] Error 1
make: *** [arch/arm/common] Error 2

Re: [patch 2.6.20-rc3 1/3] rtc-cmos driver

[David Brownell]

[-- Attachment #1: Type: text/plain, Size: 2285 bytes --]

On Tuesday 09 January 2007 8:37 am, Woody Suwalski wrote:

> As to the patch: applied to 2.6.20-rc4, both on PC and ARM, commented 
> out "EXPERIMENTAL"...
> 
> To build your new patch for ARM I have modified the line "depends on 
> RTC_CLASS && (X86_PC || ACPI || ARM)"...
> 
> On Netwinder ARM - can not build (see: rtc_build.log)

Heh, so it's a good thing I disabled the build there.  :)


> OK, changed the include/asm/rtc.h to look like i386 == include 
> asm-generic/rtc.h

In drivers/rtc/rtc-cmos.c I hope ...  <asm/rtc.h> seems to not
give equivalent functionality even on platforms which have it.

Looks to me like <asm-generic/rtc.h> is the right solution, though
that still implies arch-level support for <asm/mc146818rtc.h> which
does not exist on all platforms.

So the attached version of the rtc-cmos patch uses asm-generic
and also adds Kconfig dependencies for architectures with usable
versions of that header.

Of course, the "right" answer is to make this be like any other
driver and allow the registers to go anywhere in the address space,
not hard-wiring them to a platform-specific I/O space address.
That is, CMOS_READ/CMOS_WRITE are legacy baggage.  But that's not
an issue to be addressed by this particular patch.


> Still does not build - see rtc_build2.log
> 
> Could you please check what other defs are missing on ARM?

I'm not sure what you changed.  I updated the rtc-cmos patch to
use <asm-generic/rtc.h> directly, then did an ARM build which
configured that driver as a module.  No compile-time problems.
(I think you changed the wrong file...)

But at link time I ran into the problem that arm/kernel/time.c
defines "rtc_lock" but only exports it to an obsolete SA1100
driver.  See attached "rtc-arm.patch".

But static linking was no problem ... of course, I didn't add
any code to define the platform_device (with or without the
platform_data teling about extra registers) and couldn't test
anything other than the build.


>  >>>
> <anderson@netsweng.com>
> As for the RTC patch, it does work on the shark, and is needed.
> <<<
> 
> So is there a reason to have RTC build blocked on all ARM?

The original reason was that it's not known to work.  Given
the attached patches, that issue is resolved at least from
the build perspective.

- Dave

[-- Attachment #2: rtc-arm.patch --]
[-- Type: text/x-diff, Size: 886 bytes --]

Fix build problem on ARM ... the only user of "rtc_lock" today is the
optional PC-style "CMOS" RTC driver, not the legacy SA1100 RTC driver.

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

Index: at91/arch/arm/kernel/time.c
===================================================================
--- at91.orig/arch/arm/kernel/time.c	2006-11-10 09:47:46.000000000 -0800
+++ at91/arch/arm/kernel/time.c	2007-01-09 15:08:39.000000000 -0800
@@ -38,12 +38,14 @@
  */
 struct sys_timer *system_timer;
 
+#if defined(CONFIG_RTC_DRV_CMOS) || defined(CONFIG_RTC_DRV_CMOS_MODULE)
 /* this needs a better home */
 DEFINE_SPINLOCK(rtc_lock);
 
-#ifdef CONFIG_SA1100_RTC_MODULE
+#ifdef CONFIG_RTC_DRV_CMOS_MODULE
 EXPORT_SYMBOL(rtc_lock);
 #endif
+#endif	/* pc-style 'CMOS' RTC support */
 
 /* change this if you have some constant time drift */
 #define USECS_PER_JIFFY	(1000000/HZ)

[-- Attachment #3: rtc-cmos-2.patch --]
[-- Type: text/x-diff, Size: 23291 bytes --]

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.

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

---
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 (no CMOS_READ/CMOS_WRITE, or even normal readb
and writeb), but otherwise those chips should be compatible.

 drivers/rtc/Kconfig         |   13 
 drivers/rtc/Makefile        |    1 
 drivers/rtc/rtc-cmos.c      |  723 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/mc146818rtc.h |   10 
 4 files changed, 747 insertions(+)

Index: g26/drivers/rtc/Kconfig
===================================================================
--- g26.orig/drivers/rtc/Kconfig	2007-01-07 17:42:43.000000000 -0800
+++ g26/drivers/rtc/Kconfig	2007-01-09 14:36:23.000000000 -0800
@@ -95,6 +95,19 @@ config RTC_INTF_DEV_UIE_EMUL
 comment "RTC drivers"
 	depends on RTC_CLASS
 
+config RTC_DRV_CMOS
+	tristate "PC-style 'CMOS' real time clock"
+	depends on RTC_CLASS
+	help
+	  Say "yes" here to get direct support for the real time clock
+	  found in every PC or ACPI-based system, and some others.
+	  Specifically the original MC146818, compatibles like those in
+	  PC south bridges, the DS12887 or M48T86, some multifunction
+	  or LPC bus chips, and so on.
+
+	  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
Index: g26/drivers/rtc/Makefile
===================================================================
--- g26.orig/drivers/rtc/Makefile	2007-01-07 17:42:43.000000000 -0800
+++ g26/drivers/rtc/Makefile	2007-01-07 17:54:21.000000000 -0800
@@ -15,6 +15,7 @@ obj-$(CONFIG_RTC_INTF_SYSFS)	+= rtc-sysf
 obj-$(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
Index: g26/include/linux/mc146818rtc.h
===================================================================
--- g26.orig/include/linux/mc146818rtc.h	2007-01-07 17:42:43.000000000 -0800
+++ g26/include/linux/mc146818rtc.h	2007-01-07 17:54:21.000000000 -0800
@@ -18,6 +18,16 @@
 #ifdef __KERNEL__
 #include <linux/spinlock.h>		/* spinlock_t */
 extern spinlock_t rtc_lock;		/* serialize CMOS RAM access */
+
+/* Some RTCs extend the mc146818 register set to support alarms of more
+ * than 24 hours in the future; or dates that include a century code.
+ * This platform_data structure can pass this information to the driver.
+ */
+struct cmos_rtc_board_info {
+	u8	rtc_day_alarm;		/* zero, or register index */
+	u8	rtc_mon_alarm;		/* zero, or register index */
+	u8	rtc_century;		/* zero, or register index */
+};
 #endif
 
 /**********************************************************************
Index: g26/drivers/rtc/rtc-cmos.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ g26/drivers/rtc/rtc-cmos.c	2007-01-09 14:26:08.000000000 -0800
@@ -0,0 +1,723 @@
+/*
+ * 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;
+
+	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
+
+/*----------------------------------------------------------------*/
+
+/* On ACPI systems, the device node may be created as either a PNP
+ * device or a platform_device.  In either case the FADT data should
+ * have been transferred to us through platform_data.
+ */
+
+#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 ... including non-PC and non-ACPI platforms.
+ */
+
+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("'CMOS' RTC driver:  PCs, ACPI, etc");
+MODULE_LICENSE("GPL");

Re: [patch 2.6.20-rc3 1/3] rtc-cmos driver

[David Brownell]

[-- Attachment #1: Type: text/plain, Size: 329 bytes --]

On Tuesday 09 January 2007 4:01 pm, David Brownell wrote:
> So the attached version of the rtc-cmos patch uses asm-generic
> and also adds Kconfig dependencies for architectures with usable
> versions of that header.

No really ... _this_ version.  I seem to have too many versions
floating around, in too many different trees.


[-- Attachment #2: rtc-cmos-2.patch --]
[-- Type: text/x-diff, Size: 23850 bytes --]

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.

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

---
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.

 drivers/rtc/Kconfig         |   13 
 drivers/rtc/Makefile        |    1 
 drivers/rtc/rtc-cmos.c      |  718 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/mc146818rtc.h |   10 
 4 files changed, 742 insertions(+)

Index: g26/drivers/rtc/Kconfig
===================================================================
--- g26.orig/drivers/rtc/Kconfig	2007-01-07 17:42:43.000000000 -0800
+++ g26/drivers/rtc/Kconfig	2007-01-09 15:41:06.000000000 -0800
@@ -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 || SPARC64 || SPARC)
+	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
Index: g26/drivers/rtc/Makefile
===================================================================
--- g26.orig/drivers/rtc/Makefile	2007-01-07 17:42:43.000000000 -0800
+++ g26/drivers/rtc/Makefile	2007-01-07 17:54:21.000000000 -0800
@@ -15,6 +15,7 @@ obj-$(CONFIG_RTC_INTF_SYSFS)	+= rtc-sysf
 obj-$(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
Index: g26/include/linux/mc146818rtc.h
===================================================================
--- g26.orig/include/linux/mc146818rtc.h	2007-01-07 17:42:43.000000000 -0800
+++ g26/include/linux/mc146818rtc.h	2007-01-07 17:54:21.000000000 -0800
@@ -18,6 +18,16 @@
 #ifdef __KERNEL__
 #include <linux/spinlock.h>		/* spinlock_t */
 extern spinlock_t rtc_lock;		/* serialize CMOS RAM access */
+
+/* Some RTCs extend the mc146818 register set to support alarms of more
+ * than 24 hours in the future; or dates that include a century code.
+ * This platform_data structure can pass this information to the driver.
+ */
+struct cmos_rtc_board_info {
+	u8	rtc_day_alarm;		/* zero, or register index */
+	u8	rtc_mon_alarm;		/* zero, or register index */
+	u8	rtc_century;		/* zero, or register index */
+};
 #endif
 
 /**********************************************************************
Index: g26/drivers/rtc/rtc-cmos.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ g26/drivers/rtc/rtc-cmos.c	2007-01-09 15:17:26.000000000 -0800
@@ -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");

Re: [patch 2.6.20-rc3 1/3] rtc-cmos driver

[Matthew Garrett]

On Fri, Jan 05, 2007 at 10:01:57AM -0800, David Brownell wrote:
> 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:

Sorry for getting to this so late - I've only just started playing with 
this driver.

> +static int cmos_read_alarm(struct device *dev, struct rtc_wkalrm *t)

This is awkward. At the very least, year will be set to -1. This then 
gets passed through to rtc_tm_to_time, which results in reading 
wakealarm providing very odd feedback. I guess the "right" fix is for 
rtc_tm_to_time to use the current values for anything that's -1?

> +	rtc_control = CMOS_READ(RTC_CONTROL);
> +	rtc_control &= ~(RTC_PIE | RTC_AIE | RTC_UIE);

Do you really want to clobber RTC_AIE on probe? If an alarm has been set 
by the BIOS, it seems a little unfair to disable it on boot.

-- 
Matthew Garrett | mjg59@srcf.ucam.org

Re: [patch 2.6.20-rc3 1/3] rtc-cmos driver

[David Brownell]

On Monday 28 May 2007, Matthew Garrett wrote:
> On Fri, Jan 05, 2007 at 10:01:57AM -0800, David Brownell wrote:
> > This is an "RTC framework" driver for the "CMOS" RTCs which are standard
> > on PCs and some other platforms.  That's MC146818 compatible silicon.
> > ...
> > +static int cmos_read_alarm(struct device *dev, struct rtc_wkalrm *t)
> 
> This is awkward. At the very least, year will be set to -1. This then 
> gets passed through to rtc_tm_to_time, which results in reading 
> wakealarm providing very odd feedback. I guess the "right" fix is for 
> rtc_tm_to_time to use the current values for anything that's -1?

Well ... legacy APIs allow "-1" there; /proc/driver/rtc certainly
interprets wildcards consistently too.  That is, historically it's
not been legit to call rtc_tm_to_time(&t->time).

A counter-argument could be made that rtc_read_alarm() should get
rid of wildcards.  It's got the right RTC in hand; rtc_tm_to_time()
doesn't.  Other RTCs can have this same type of "wildcard" issue.

Me, I'd prefer to make the API treat alarms as purely oneshot.
That whole "wildcard" model is, as you noted, awkward ... even
though it's got hardware support in cases like MC146818 and clones,
it's not very portable.  But I don't want to push that issue either
way just now.



> > +	rtc_control = CMOS_READ(RTC_CONTROL);
> > +	rtc_control &= ~(RTC_PIE | RTC_AIE | RTC_UIE);
> 
> Do you really want to clobber RTC_AIE on probe? If an alarm has been set 
> by the BIOS, it seems a little unfair to disable it on boot.

I was wondering about that in the context of a different RTC, which
happens to run on BIOS-less hardware.  Which, curiously, may be the
opposite of BIOS-impaired hardware ... :)

In general, I suspect the alarm should stay active ... unless its
time has already passed.  That was the original intent of that
tweak, but of course PCs don't actually *have* oneshot alarms, so
there's no way to tell if a given alarm is in the past.  Leading to
the conclusion that AIE should probably stay enabled.

- Dave