rtc-ds1216.c

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/*
 * Dallas DS1216 RTC driver
 *
 * Copyright (c) 2007 Thomas Bogendoerfer
 *
 */

#include <linux/module.h>
#include <linux/rtc.h>
#include <linux/platform_device.h>
#include <linux/bcd.h>
#include <linux/slab.h>

#define DRV_VERSION "0.2"

struct ds1216_regs {
    u8 tsec;
    u8 sec;
    u8 min;
    u8 hour;
    u8 wday;
    u8 mday;
    u8 month;
    u8 year;
};

#define DS1216_HOUR_1224    (1 << 7)
#define DS1216_HOUR_AMPM    (1 << 5)

struct ds1216_priv {
    struct rtc_device *rtc;
    void __iomem *ioaddr;
    size_t size;
    unsigned long baseaddr;
};

static const u8 magic[] = {
    0xc5, 0x3a, 0xa3, 0x5c, 0xc5, 0x3a, 0xa3, 0x5c
};

/*
 * Read the 64 bit we'd like to have - It a series
 * of 64 bits showing up in the LSB of the base register.
 *
 */
static void ds1216_read(u8 __iomem *ioaddr, u8 *buf)
{
    unsigned char c;
    int i, j;

    for (i = 0; i < 8; i++) {
        c = 0;
        for (j = 0; j < 8; j++)
            c |= (readb(ioaddr) & 0x1) << j;
        buf[i] = c;
    }
}

static void ds1216_write(u8 __iomem *ioaddr, const u8 *buf)
{
    unsigned char c;
    int i, j;

    for (i = 0; i < 8; i++) {
        c = buf[i];
        for (j = 0; j < 8; j++) {
            writeb(c, ioaddr);
            c = c >> 1;
        }
    }
}

static void ds1216_switch_ds_to_clock(u8 __iomem *ioaddr)
{
    /* Reset magic pointer */
    readb(ioaddr);
    /* Write 64 bit magic to DS1216 */
    ds1216_write(ioaddr, magic);
}

static int ds1216_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
    struct platform_device *pdev = to_platform_device(dev);
    struct ds1216_priv *priv = platform_get_drvdata(pdev);
    struct ds1216_regs regs;

    ds1216_switch_ds_to_clock(priv->ioaddr);
    ds1216_read(priv->ioaddr, (u8 *)&regs);

    tm->tm_sec = bcd2bin(regs.sec);
    tm->tm_min = bcd2bin(regs.min);
    if (regs.hour & DS1216_HOUR_1224) {
        /* AM/PM mode */
        tm->tm_hour = bcd2bin(regs.hour & 0x1f);
        if (regs.hour & DS1216_HOUR_AMPM)
            tm->tm_hour += 12;
    } else
        tm->tm_hour = bcd2bin(regs.hour & 0x3f);
    tm->tm_wday = (regs.wday & 7) - 1;
    tm->tm_mday = bcd2bin(regs.mday & 0x3f);
    tm->tm_mon = bcd2bin(regs.month & 0x1f);
    tm->tm_year = bcd2bin(regs.year);
    if (tm->tm_year < 70)
        tm->tm_year += 100;

    return rtc_valid_tm(tm);
}

static int ds1216_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
    struct platform_device *pdev = to_platform_device(dev);
    struct ds1216_priv *priv = platform_get_drvdata(pdev);
    struct ds1216_regs regs;

    ds1216_switch_ds_to_clock(priv->ioaddr);
    ds1216_read(priv->ioaddr, (u8 *)&regs);

    regs.tsec = 0; /* clear 0.1 and 0.01 seconds */
    regs.sec = bin2bcd(tm->tm_sec);
    regs.min = bin2bcd(tm->tm_min);
    regs.hour &= DS1216_HOUR_1224;
    if (regs.hour && tm->tm_hour > 12) {
        regs.hour |= DS1216_HOUR_AMPM;
        tm->tm_hour -= 12;
    }
    regs.hour |= bin2bcd(tm->tm_hour);
    regs.wday &= ~7;
    regs.wday |= tm->tm_wday;
    regs.mday = bin2bcd(tm->tm_mday);
    regs.month = bin2bcd(tm->tm_mon);
    regs.year = bin2bcd(tm->tm_year % 100);

    ds1216_switch_ds_to_clock(priv->ioaddr);
    ds1216_write(priv->ioaddr, (u8 *)&regs);
    return 0;
}

static const struct rtc_class_ops ds1216_rtc_ops = {
    .read_time  = ds1216_rtc_read_time,
    .set_time   = ds1216_rtc_set_time,
};

static int __init ds1216_rtc_probe(struct platform_device *pdev)
{
    struct resource *res;
    struct ds1216_priv *priv;
    int ret = 0;
    u8 dummy[8];

    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if (!res)
        return -ENODEV;
    priv = kzalloc(sizeof *priv, GFP_KERNEL);
    if (!priv)
        return -ENOMEM;

    platform_set_drvdata(pdev, priv);

    priv->size = resource_size(res);
    if (!request_mem_region(res->start, priv->size, pdev->name)) {
        ret = -EBUSY;
        goto out;
    }
    priv->baseaddr = res->start;
    priv->ioaddr = ioremap(priv->baseaddr, priv->size);
    if (!priv->ioaddr) {
        ret = -ENOMEM;
        goto out;
    }
    priv->rtc = rtc_device_register("ds1216", &pdev->dev,
                  &ds1216_rtc_ops, THIS_MODULE);
    if (IS_ERR(priv->rtc)) {
        ret = PTR_ERR(priv->rtc);
        goto out;
    }

    /* dummy read to get clock into a known state */
    ds1216_read(priv->ioaddr, dummy);
    return 0;

out:
    if (priv->ioaddr)
        iounmap(priv->ioaddr);
    if (priv->baseaddr)
        release_mem_region(priv->baseaddr, priv->size);
    kfree(priv);
    return ret;
}

static int __exit ds1216_rtc_remove(struct platform_device *pdev)
{
    struct ds1216_priv *priv = platform_get_drvdata(pdev);

    rtc_device_unregister(priv->rtc);
    iounmap(priv->ioaddr);
    release_mem_region(priv->baseaddr, priv->size);
    kfree(priv);
    return 0;
}

static struct platform_driver ds1216_rtc_platform_driver = {
    .driver     = {
        .name   = "rtc-ds1216",
        .owner  = THIS_MODULE,
    },
    .remove     = __exit_p(ds1216_rtc_remove),
};

static int __init ds1216_rtc_init(void)
{
    return platform_driver_probe(&ds1216_rtc_platform_driver, ds1216_rtc_probe);
}

static void __exit ds1216_rtc_exit(void)
{
    platform_driver_unregister(&ds1216_rtc_platform_driver);
}

MODULE_AUTHOR("Thomas Bogendoerfer <[email protected]>");
MODULE_DESCRIPTION("DS1216 RTC driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(DRV_VERSION);
MODULE_ALIAS("platform:rtc-ds1216");

module_init(ds1216_rtc_init);
module_exit(ds1216_rtc_exit);