alpha: Reorganize rtc handling

Discontinue use of GENERIC_CMOS_UPDATE; rely on the RTC subsystem.

The marvel platform requires that the rtc only be touched from the
boot cpu.  This had been partially implemented with hooks for
get/set_rtc_time, but read/update_persistent_clock were not handled.
Move the hooks from the machine_vec to a special rtc_class_ops struct.

We had read_persistent_clock managing the epoch against which the
rtc hw is based, but this didn't apply to get_rtc_time or set_rtc_time.
This resulted in incorrect values when hwclock(8) gets involved.

Allow the epoch to be set from the kernel command-line, overriding
the autodetection, which is doomed to fail in 2020.  Further, by
implementing the rtc ioctl function, we can expose this epoch to
userland.

Elide the alarm functions that RTC_DRV_CMOS implements.  This was
highly questionable on Alpha, since the interrupt is used by the
system timer.

Signed-off-by: Richard Henderson <rth@twiddle.net>

1 files changed, 323 insertions, 0 deletions

diff --git a/arch/alpha/kernel/rtc.c b/arch/alpha/kernel/rtc.c
new file mode 100644
index 000000000000..c8d284d8521f
--- /dev/null
+++ b/arch/alpha/kernel/rtc.c
@@ -0,0 +1,323 @@
+/*
+ *  linux/arch/alpha/kernel/rtc.c
+ *
+ *  Copyright (C) 1991, 1992, 1995, 1999, 2000  Linus Torvalds
+ *
+ * This file contains date handling.
+ */
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/param.h>
+#include <linux/string.h>
+#include <linux/mc146818rtc.h>
+#include <linux/bcd.h>
+#include <linux/rtc.h>
+#include <linux/platform_device.h>
+
+#include <asm/rtc.h>
+
+#include "proto.h"
+
+
+/*
+ * Support for the RTC device.
+ *
+ * We don't want to use the rtc-cmos driver, because we don't want to support
+ * alarms, as that would be indistinguishable from timer interrupts.
+ *
+ * Further, generic code is really, really tied to a 1900 epoch.  This is
+ * true in __get_rtc_time as well as the users of struct rtc_time e.g.
+ * rtc_tm_to_time.  Thankfully all of the other epochs in use are later
+ * than 1900, and so it's easy to adjust.
+ */
+
+static unsigned long rtc_epoch;
+
+static int __init
+specifiy_epoch(char *str)
+{
+	unsigned long epoch = simple_strtoul(str, NULL, 0);
+	if (epoch < 1900)
+		printk("Ignoring invalid user specified epoch %lu\n", epoch);
+	else
+		rtc_epoch = epoch;
+	return 1;
+}
+__setup("epoch=", specifiy_epoch);
+
+static void __init
+init_rtc_epoch(void)
+{
+	int epoch, year, ctrl;
+
+	if (rtc_epoch != 0) {
+		/* The epoch was specified on the command-line.  */
+		return;
+	}
+
+	/* Detect the epoch in use on this computer.  */
+	ctrl = CMOS_READ(RTC_CONTROL);
+	year = CMOS_READ(RTC_YEAR);
+	if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
+		year = bcd2bin(year);
+
+	/* PC-like is standard; used for year >= 70 */
+	epoch = 1900;
+	if (year < 20) {
+		epoch = 2000;
+	} else if (year >= 20 && year < 48) {
+		/* NT epoch */
+		epoch = 1980;
+	} else if (year >= 48 && year < 70) {
+		/* Digital UNIX epoch */
+		epoch = 1952;
+	}
+	rtc_epoch = epoch;
+
+	printk(KERN_INFO "Using epoch %d for rtc year %d\n", epoch, year);
+}
+
+static int
+alpha_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	__get_rtc_time(tm);
+
+	/* Adjust for non-default epochs.  It's easier to depend on the
+	   generic __get_rtc_time and adjust the epoch here than create
+	   a copy of __get_rtc_time with the edits we need.  */
+	if (rtc_epoch != 1900) {
+		int year = tm->tm_year;
+		/* Undo the century adjustment made in __get_rtc_time.  */
+		if (year >= 100)
+			year -= 100;
+		year += rtc_epoch - 1900;
+		/* Redo the century adjustment with the epoch in place.  */
+		if (year <= 69)
+			year += 100;
+		tm->tm_year = year;
+	}
+
+	return rtc_valid_tm(tm);
+}
+
+static int
+alpha_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rtc_time xtm;
+
+	if (rtc_epoch != 1900) {
+		xtm = *tm;
+		xtm.tm_year -= rtc_epoch - 1900;
+		tm = &xtm;
+	}
+
+	return __set_rtc_time(tm);
+}
+
+static int
+alpha_rtc_set_mmss(struct device *dev, unsigned long nowtime)
+{
+	int retval = 0;
+	int real_seconds, real_minutes, cmos_minutes;
+	unsigned char save_control, save_freq_select;
+
+	/* Note: This code only updates minutes and seconds.  Comments
+	   indicate this was to avoid messing with unknown time zones,
+	   and with the epoch nonsense described above.  In order for
+	   this to work, the existing clock cannot be off by more than
+	   15 minutes.
+
+	   ??? This choice is may be out of date.  The x86 port does
+	   not have problems with timezones, and the epoch processing has
+	   now been fixed in alpha_set_rtc_time.
+
+	   In either case, one can always force a full rtc update with
+	   the userland hwclock program, so surely 15 minute accuracy
+	   is no real burden.  */
+
+	/* In order to set the CMOS clock precisely, we have to be called
+	   500 ms after the second nowtime has started, because when
+	   nowtime is written into the registers of the CMOS clock, it will
+	   jump to the next second precisely 500 ms later. Check the Motorola
+	   MC146818A or Dallas DS12887 data sheet for details.  */
+
+	/* irq are locally disabled here */
+	spin_lock(&rtc_lock);
+	/* Tell the clock it's being set */
+	save_control = CMOS_READ(RTC_CONTROL);
+	CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
+
+	/* Stop and reset prescaler */
+	save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
+	CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
+
+	cmos_minutes = CMOS_READ(RTC_MINUTES);
+	if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
+		cmos_minutes = bcd2bin(cmos_minutes);
+
+	real_seconds = nowtime % 60;
+	real_minutes = nowtime / 60;
+	if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1) {
+		/* correct for half hour time zone */
+		real_minutes += 30;
+	}
+	real_minutes %= 60;
+
+	if (abs(real_minutes - cmos_minutes) < 30) {
+		if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
+			real_seconds = bin2bcd(real_seconds);
+			real_minutes = bin2bcd(real_minutes);
+		}
+		CMOS_WRITE(real_seconds,RTC_SECONDS);
+		CMOS_WRITE(real_minutes,RTC_MINUTES);
+	} else {
+		printk_once(KERN_NOTICE
+			    "set_rtc_mmss: can't update from %d to %d\n",
+			    cmos_minutes, real_minutes);
+		retval = -1;
+	}
+
+	/* The following flags have to be released exactly in this order,
+	 * otherwise the DS12887 (popular MC146818A clone with integrated
+	 * battery and quartz) will not reset the oscillator and will not
+	 * update precisely 500 ms later. You won't find this mentioned in
+	 * the Dallas Semiconductor data sheets, but who believes data
+	 * sheets anyway ...                           -- Markus Kuhn
+	 */
+	CMOS_WRITE(save_control, RTC_CONTROL);
+	CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
+	spin_unlock(&rtc_lock);
+
+	return retval;
+}
+
+static int
+alpha_rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
+{
+	switch (cmd) {
+	case RTC_EPOCH_READ:
+		return put_user(rtc_epoch, (unsigned long __user *)arg);
+	case RTC_EPOCH_SET:
+		if (arg < 1900)
+			return -EINVAL;
+		rtc_epoch = arg;
+		return 0;
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+
+static const struct rtc_class_ops alpha_rtc_ops = {
+	.read_time = alpha_rtc_read_time,
+	.set_time = alpha_rtc_set_time,
+	.set_mmss = alpha_rtc_set_mmss,
+	.ioctl = alpha_rtc_ioctl,
+};
+
+/*
+ * Similarly, except do the actual CMOS access on the boot cpu only.
+ * This requires marshalling the data across an interprocessor call.
+ */
+
+#if defined(CONFIG_SMP) && \
+    (defined(CONFIG_ALPHA_GENERIC) || defined(CONFIG_ALPHA_MARVEL))
+# define HAVE_REMOTE_RTC 1
+
+union remote_data {
+	struct rtc_time *tm;
+	unsigned long now;
+	long retval;
+};
+
+static void
+do_remote_read(void *data)
+{
+	union remote_data *x = data;
+	x->retval = alpha_rtc_read_time(NULL, x->tm);
+}
+
+static int
+remote_read_time(struct device *dev, struct rtc_time *tm)
+{
+	union remote_data x;
+	if (smp_processor_id() != boot_cpuid) {
+		x.tm = tm;
+		smp_call_function_single(boot_cpuid, do_remote_read, &x, 1);
+		return x.retval;
+	}
+	return alpha_rtc_read_time(NULL, tm);
+}
+
+static void
+do_remote_set(void *data)
+{
+	union remote_data *x = data;
+	x->retval = alpha_rtc_set_time(NULL, x->tm);
+}
+
+static int
+remote_set_time(struct device *dev, struct rtc_time *tm)
+{
+	union remote_data x;
+	if (smp_processor_id() != boot_cpuid) {
+		x.tm = tm;
+		smp_call_function_single(boot_cpuid, do_remote_set, &x, 1);
+		return x.retval;
+	}
+	return alpha_rtc_set_time(NULL, tm);
+}
+
+static void
+do_remote_mmss(void *data)
+{
+	union remote_data *x = data;
+	x->retval = alpha_rtc_set_mmss(NULL, x->now);
+}
+
+static int
+remote_set_mmss(struct device *dev, unsigned long now)
+{
+	union remote_data x;
+	if (smp_processor_id() != boot_cpuid) {
+		x.now = now;
+		smp_call_function_single(boot_cpuid, do_remote_mmss, &x, 1);
+		return x.retval;
+	}
+	return alpha_rtc_set_mmss(NULL, now);
+}
+
+static const struct rtc_class_ops remote_rtc_ops = {
+	.read_time = remote_read_time,
+	.set_time = remote_set_time,
+	.set_mmss = remote_set_mmss,
+	.ioctl = alpha_rtc_ioctl,
+};
+#endif
+
+static int __init
+alpha_rtc_init(void)
+{
+	const struct rtc_class_ops *ops;
+	struct platform_device *pdev;
+	struct rtc_device *rtc;
+	const char *name;
+
+	init_rtc_epoch();
+	name = "rtc-alpha";
+	ops = &alpha_rtc_ops;
+
+#ifdef HAVE_REMOTE_RTC
+	if (alpha_mv.rtc_boot_cpu_only)
+		ops = &remote_rtc_ops;
+#endif
+
+	pdev = platform_device_register_simple(name, -1, NULL, 0);
+	rtc = devm_rtc_device_register(&pdev->dev, name, ops, THIS_MODULE);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	platform_set_drvdata(pdev, rtc);
+	return 0;
+}
+device_initcall(alpha_rtc_init);