rtc.c

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/*
 * RTC related functions
 */
#include <linux/platform_device.h>
#include <linux/mc146818rtc.h>
#include <linux/acpi.h>
#include <linux/bcd.h>
#include <linux/export.h>
#include <linux/pnp.h>
#include <linux/of.h>

#include <asm/vsyscall.h>
#include <asm/x86_init.h>
#include <asm/time.h>
#include <asm/mrst.h>

#ifdef CONFIG_X86_32
/*
 * This is a special lock that is owned by the CPU and holds the index
 * register we are working with.  It is required for NMI access to the
 * CMOS/RTC registers.  See include/asm-i386/mc146818rtc.h for details.
 */
volatile unsigned long cmos_lock;
EXPORT_SYMBOL(cmos_lock);
#endif /* CONFIG_X86_32 */

/* For two digit years assume time is always after that */
#define CMOS_YEARS_OFFS 2000

DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);

/*
 * In order to set the CMOS clock precisely, set_rtc_mmss has 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.
 *
 * BUG: This routine does not handle hour overflow properly; it just
 *      sets the minutes. Usually you'll only notice that after reboot!
 */
int mach_set_rtc_mmss(unsigned long nowtime)
{
    int real_seconds, real_minutes, cmos_minutes;
    unsigned char save_control, save_freq_select;
    unsigned long flags;
    int retval = 0;

    spin_lock_irqsave(&rtc_lock, flags);

     /* 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);

    /*
     * since we're only adjusting minutes and seconds,
     * don't interfere with hour overflow. This avoids
     * messing with unknown time zones but requires your
     * RTC not to be off by more than 15 minutes
     */
    real_seconds = nowtime % 60;
    real_minutes = nowtime / 60;
    /* correct for half hour time zone */
    if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
        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_irqrestore(&rtc_lock, flags);

    return retval;
}

unsigned long mach_get_cmos_time(void)
{
    unsigned int status, year, mon, day, hour, min, sec, century = 0;
    unsigned long flags;

    spin_lock_irqsave(&rtc_lock, flags);

    /*
     * If UIP is clear, then we have >= 244 microseconds before
     * RTC registers will be updated.  Spec sheet says that this
     * is the reliable way to read RTC - registers. If UIP is set
     * then the register access might be invalid.
     */
    while ((CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
        cpu_relax();

    sec = CMOS_READ(RTC_SECONDS);
    min = CMOS_READ(RTC_MINUTES);
    hour = CMOS_READ(RTC_HOURS);
    day = CMOS_READ(RTC_DAY_OF_MONTH);
    mon = CMOS_READ(RTC_MONTH);
    year = CMOS_READ(RTC_YEAR);

#ifdef CONFIG_ACPI
    if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
        acpi_gbl_FADT.century)
        century = CMOS_READ(acpi_gbl_FADT.century);
#endif

    status = CMOS_READ(RTC_CONTROL);
    WARN_ON_ONCE(RTC_ALWAYS_BCD && (status & RTC_DM_BINARY));

    spin_unlock_irqrestore(&rtc_lock, flags);

    if (RTC_ALWAYS_BCD || !(status & RTC_DM_BINARY)) {
        sec = bcd2bin(sec);
        min = bcd2bin(min);
        hour = bcd2bin(hour);
        day = bcd2bin(day);
        mon = bcd2bin(mon);
        year = bcd2bin(year);
    }

    if (century) {
        century = bcd2bin(century);
        year += century * 100;
        printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
    } else
        year += CMOS_YEARS_OFFS;

    return mktime(year, mon, day, hour, min, sec);
}

/* Routines for accessing the CMOS RAM/RTC. */
unsigned char rtc_cmos_read(unsigned char addr)
{
    unsigned char val;

    lock_cmos_prefix(addr);
    outb(addr, RTC_PORT(0));
    val = inb(RTC_PORT(1));
    lock_cmos_suffix(addr);

    return val;
}
EXPORT_SYMBOL(rtc_cmos_read);

void rtc_cmos_write(unsigned char val, unsigned char addr)
{
    lock_cmos_prefix(addr);
    outb(addr, RTC_PORT(0));
    outb(val, RTC_PORT(1));
    lock_cmos_suffix(addr);
}
EXPORT_SYMBOL(rtc_cmos_write);

int update_persistent_clock(struct timespec now)
{
    return x86_platform.set_wallclock(now.tv_sec);
}

/* not static: needed by APM */
void read_persistent_clock(struct timespec *ts)
{
    unsigned long retval;

    retval = x86_platform.get_wallclock();

    ts->tv_sec = retval;
    ts->tv_nsec = 0;
}

unsigned long long native_read_tsc(void)
{
    return __native_read_tsc();
}
EXPORT_SYMBOL(native_read_tsc);


static struct resource rtc_resources[] = {
    [0] = {
        .start  = RTC_PORT(0),
        .end    = RTC_PORT(1),
        .flags  = IORESOURCE_IO,
    },
    [1] = {
        .start  = RTC_IRQ,
        .end    = RTC_IRQ,
        .flags  = IORESOURCE_IRQ,
    }
};

static struct platform_device rtc_device = {
    .name       = "rtc_cmos",
    .id     = -1,
    .resource   = rtc_resources,
    .num_resources  = ARRAY_SIZE(rtc_resources),
};

static __init int add_rtc_cmos(void)
{
#ifdef CONFIG_PNP
    static const char * const  const ids[] __initconst =
        { "PNP0b00", "PNP0b01", "PNP0b02", };
    struct pnp_dev *dev;
    struct pnp_id *id;
    int i;

    pnp_for_each_dev(dev) {
        for (id = dev->id; id; id = id->next) {
            for (i = 0; i < ARRAY_SIZE(ids); i++) {
                if (compare_pnp_id(id, ids[i]) != 0)
                    return 0;
            }
        }
    }
#endif
    if (of_have_populated_dt())
        return 0;

    /* Intel MID platforms don't have ioport rtc */
    if (mrst_identify_cpu())
        return -ENODEV;

    platform_device_register(&rtc_device);
    dev_info(&rtc_device.dev,
         "registered platform RTC device (no PNP device found)\n");

    return 0;
}
device_initcall(add_rtc_cmos);