path: root/drivers/rtc/rtc-cmos.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 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)
 */

/*
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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/log2.h>
#include <linux/pm.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#ifdef CONFIG_X86
#include <asm/i8259.h>
#include <asm/processor.h>
#include <linux/dmi.h>
#endif

/* this is for "generic access to PC-style RTC" using CMOS_READ/CMOS_WRITE */
#include <linux/mc146818rtc.h>

#ifdef CONFIG_ACPI
/*
 * Use ACPI SCI to replace HPET interrupt for RTC Alarm event
 *
 * If cleared, ACPI SCI is only used to wake up the system from suspend
 *
 * If set, ACPI SCI is used to handle UIE/AIE and system wakeup
 */

static bool use_acpi_alarm;
module_param(use_acpi_alarm, bool, 0444);

static inline int cmos_use_acpi_alarm(void)
{
	return use_acpi_alarm;
}
#else /* !CONFIG_ACPI */

static inline int cmos_use_acpi_alarm(void)
{
	return 0;
}
#endif

struct cmos_rtc {
	struct rtc_device	*rtc;
	struct device		*dev;
	int			irq;
	struct resource		*iomem;
	time64_t		alarm_expires;

	void			(*wake_on)(struct device *);
	void			(*wake_off)(struct device *);

	u8			enabled_wake;
	u8			suspend_ctrl;

	/* newer hardware extends the original register set */
	u8			day_alrm;
	u8			mon_alrm;
	u8			century;

	struct rtc_wkalrm	saved_wkalrm;
};

/* 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";

/* The RTC_INTR register may have e.g. RTC_PF set even if RTC_PIE is clear;
 * always mask it against the irq enable bits in RTC_CONTROL.  Bit values
 * are the same: PF==PIE, AF=AIE, UF=UIE; so RTC_IRQMASK works with both.
 */
#define	RTC_IRQMASK	(RTC_PF | RTC_AF | RTC_UF)

static inline int is_intr(u8 rtc_intr)
{
	if (!(rtc_intr & RTC_IRQF))
		return 0;
	return rtc_intr & RTC_IRQMASK;
}

/*----------------------------------------------------------------*/

/* Much modern x86 hardware has HPETs (10+ MHz timers) which, because
 * many BIOS programmers don't set up "sane mode" IRQ routing, are mostly
 * used in a broken "legacy replacement" mode.  The breakage includes
 * HPET #1 hijacking the IRQ for this RTC, and being unavailable for
 * other (better) use.
 *
 * When that broken mode is in use, platform glue provides a partial
 * emulation of hardware RTC IRQ facilities using HPET #1.  We don't
 * want to use HPET for anything except those IRQs though...
 */
#ifdef CONFIG_HPET_EMULATE_RTC
#include <asm/hpet.h>
#else

static inline int is_hpet_enabled(void)
{
	return 0;
}

static inline int hpet_mask_rtc_irq_bit(unsigned long mask)
{
	return 0;
}

static inline int hpet_set_rtc_irq_bit(unsigned long mask)
{
	return 0;
}

static inline int
hpet_set_alarm_time(unsigned char hrs, unsigned char min, unsigned char sec)
{
	return 0;
}

static inline int hpet_set_periodic_freq(unsigned long freq)
{
	return 0;
}

static inline int hpet_rtc_timer_init(void)
{
	return 0;
}

extern irq_handler_t hpet_rtc_interrupt;

static inline int hpet_register_irq_handler(irq_handler_t handler)
{
	return 0;
}

static inline int hpet_unregister_irq_handler(irq_handler_t handler)
{
	return 0;
}

#endif

/* Don't use HPET for RTC Alarm event if ACPI Fixed event is used */
static inline int use_hpet_alarm(void)
{
	return is_hpet_enabled() && !cmos_use_acpi_alarm();
}

/*----------------------------------------------------------------*/

#ifdef RTC_PORT

/* Most newer x86 systems have two register banks, the first used
 * for RTC and NVRAM and the second only for NVRAM.  Caller must
 * own rtc_lock ... and we won't worry about access during NMI.
 */
#define can_bank2	true

static inline unsigned char cmos_read_bank2(unsigned char addr)
{
	outb(addr, RTC_PORT(2));
	return inb(RTC_PORT(3));
}

static inline void cmos_write_bank2(unsigned char val, unsigned char addr)
{
	outb(addr, RTC_PORT(2));
	outb(val, RTC_PORT(3));
}

#else

#define can_bank2	false

static inline unsigned char cmos_read_bank2(unsigned char addr)
{
	return 0;
}

static inline void cmos_write_bank2(unsigned char val, unsigned char addr)
{
}

#endif

/*----------------------------------------------------------------*/

static int cmos_read_time(struct device *dev, struct rtc_time *t)
{
	int ret;

	/*
	 * If pm_trace abused the RTC for storage, set the timespec to 0,
	 * which tells the caller that this RTC value is unusable.
	 */
	if (!pm_trace_rtc_valid())
		return -EIO;

	ret = mc146818_get_time(t, 1000);
	if (ret < 0) {
		dev_err_ratelimited(dev, "unable to read current time\n");
		return ret;
	}

	return 0;
}

static int cmos_set_time(struct device *dev, struct rtc_time *t)
{
	/* 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