rtc-ds2404.c

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/*
 * Copyright (C) 2012 Sven Schnelle <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#include <linux/platform_device.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/rtc.h>
#include <linux/types.h>
#include <linux/bcd.h>
#include <linux/rtc-ds2404.h>
#include <linux/delay.h>
#include <linux/gpio.h>
#include <linux/slab.h>

#include <linux/io.h>

#define DS2404_STATUS_REG 0x200
#define DS2404_CONTROL_REG 0x201
#define DS2404_RTC_REG 0x202

#define DS2404_WRITE_SCRATCHPAD_CMD 0x0f
#define DS2404_READ_SCRATCHPAD_CMD 0xaa
#define DS2404_COPY_SCRATCHPAD_CMD 0x55
#define DS2404_READ_MEMORY_CMD 0xf0

struct ds2404;

struct ds2404_chip_ops {
    int (*map_io)(struct ds2404 *chip, struct platform_device *pdev,
              struct ds2404_platform_data *pdata);
    void (*unmap_io)(struct ds2404 *chip);
};

#define DS2404_RST  0
#define DS2404_CLK  1
#define DS2404_DQ   2

struct ds2404_gpio {
    const char *name;
    unsigned int gpio;
};

struct ds2404 {
    struct ds2404_gpio *gpio;
    struct ds2404_chip_ops *ops;
    struct rtc_device *rtc;
};

static struct ds2404_gpio ds2404_gpio[] = {
    { "RTC RST", 0 },
    { "RTC CLK", 0 },
    { "RTC DQ", 0 },
};

static int ds2404_gpio_map(struct ds2404 *chip, struct platform_device *pdev,
              struct ds2404_platform_data *pdata)
{
    int i, err;

    ds2404_gpio[DS2404_RST].gpio = pdata->gpio_rst;
    ds2404_gpio[DS2404_CLK].gpio = pdata->gpio_clk;
    ds2404_gpio[DS2404_DQ].gpio = pdata->gpio_dq;

    for (i = 0; i < ARRAY_SIZE(ds2404_gpio); i++) {
        err = gpio_request(ds2404_gpio[i].gpio, ds2404_gpio[i].name);
        if (err) {
            printk(KERN_ERR "error mapping gpio %s: %d\n",
                ds2404_gpio[i].name, err);
            goto err_request;
        }
        if (i != DS2404_DQ)
            gpio_direction_output(ds2404_gpio[i].gpio, 1);
    }

    chip->gpio = ds2404_gpio;
    return 0;

err_request:
    while (--i >= 0)
        gpio_free(ds2404_gpio[i].gpio);
    return err;
}

static void ds2404_gpio_unmap(struct ds2404 *chip)
{
    int i;

    for (i = 0; i < ARRAY_SIZE(ds2404_gpio); i++)
        gpio_free(ds2404_gpio[i].gpio);
}

static struct ds2404_chip_ops ds2404_gpio_ops = {
    .map_io     = ds2404_gpio_map,
    .unmap_io   = ds2404_gpio_unmap,
};

static void ds2404_reset(struct device *dev)
{
    gpio_set_value(ds2404_gpio[DS2404_RST].gpio, 0);
    udelay(1000);
    gpio_set_value(ds2404_gpio[DS2404_RST].gpio, 1);
    gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
    gpio_direction_output(ds2404_gpio[DS2404_DQ].gpio, 0);
    udelay(10);
}

static void ds2404_write_byte(struct device *dev, u8 byte)
{
    int i;

    gpio_direction_output(ds2404_gpio[DS2404_DQ].gpio, 1);
    for (i = 0; i < 8; i++) {
        gpio_set_value(ds2404_gpio[DS2404_DQ].gpio, byte & (1 << i));
        udelay(10);
        gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 1);
        udelay(10);
        gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
        udelay(10);
    }
}

static u8 ds2404_read_byte(struct device *dev)
{
    int i;
    u8 ret = 0;

    gpio_direction_input(ds2404_gpio[DS2404_DQ].gpio);

    for (i = 0; i < 8; i++) {
        gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 0);
        udelay(10);
        if (gpio_get_value(ds2404_gpio[DS2404_DQ].gpio))
            ret |= 1 << i;
        gpio_set_value(ds2404_gpio[DS2404_CLK].gpio, 1);
        udelay(10);
    }
    return ret;
}

static void ds2404_read_memory(struct device *dev, u16 offset,
                   int length, u8 *out)
{
    ds2404_reset(dev);
    ds2404_write_byte(dev, DS2404_READ_MEMORY_CMD);
    ds2404_write_byte(dev, offset & 0xff);
    ds2404_write_byte(dev, (offset >> 8) & 0xff);
    while (length--)
        *out++ = ds2404_read_byte(dev);
}

static void ds2404_write_memory(struct device *dev, u16 offset,
                int length, u8 *out)
{
    int i;
    u8 ta01, ta02, es;

    ds2404_reset(dev);
    ds2404_write_byte(dev, DS2404_WRITE_SCRATCHPAD_CMD);
    ds2404_write_byte(dev, offset & 0xff);
    ds2404_write_byte(dev, (offset >> 8) & 0xff);

    for (i = 0; i < length; i++)
        ds2404_write_byte(dev, out[i]);

    ds2404_reset(dev);
    ds2404_write_byte(dev, DS2404_READ_SCRATCHPAD_CMD);

    ta01 = ds2404_read_byte(dev);
    ta02 = ds2404_read_byte(dev);
    es = ds2404_read_byte(dev);

    for (i = 0; i < length; i++) {
        if (out[i] != ds2404_read_byte(dev)) {
            printk(KERN_ERR "read invalid data\n");
            return;
        }
    }

    ds2404_reset(dev);
    ds2404_write_byte(dev, DS2404_COPY_SCRATCHPAD_CMD);
    ds2404_write_byte(dev, ta01);
    ds2404_write_byte(dev, ta02);
    ds2404_write_byte(dev, es);

    gpio_direction_input(ds2404_gpio[DS2404_DQ].gpio);
    while (gpio_get_value(ds2404_gpio[DS2404_DQ].gpio))
        ;
}

static void ds2404_enable_osc(struct device *dev)
{
    u8 in[1] = { 0x10 }; /* enable oscillator */
    ds2404_write_memory(dev, 0x201, 1, in);
}

static int ds2404_read_time(struct device *dev, struct rtc_time *dt)
{
    unsigned long time = 0;

    ds2404_read_memory(dev, 0x203, 4, (u8 *)&time);
    time = le32_to_cpu(time);

    rtc_time_to_tm(time, dt);
    return rtc_valid_tm(dt);
}

static int ds2404_set_mmss(struct device *dev, unsigned long secs)
{
    u32 time = cpu_to_le32(secs);
    ds2404_write_memory(dev, 0x203, 4, (u8 *)&time);
    return 0;
}

static const struct rtc_class_ops ds2404_rtc_ops = {
    .read_time  = ds2404_read_time,
    .set_mmss   = ds2404_set_mmss,
};

static int rtc_probe(struct platform_device *pdev)
{
    struct ds2404_platform_data *pdata = pdev->dev.platform_data;
    struct ds2404 *chip;
    int retval = -EBUSY;

    chip = kzalloc(sizeof(struct ds2404), GFP_KERNEL);
    if (!chip)
        return -ENOMEM;

    chip->ops = &ds2404_gpio_ops;

    retval = chip->ops->map_io(chip, pdev, pdata);
    if (retval)
        goto err_chip;

    dev_info(&pdev->dev, "using GPIOs RST:%d, CLK:%d, DQ:%d\n",
         chip->gpio[DS2404_RST].gpio, chip->gpio[DS2404_CLK].gpio,
         chip->gpio[DS2404_DQ].gpio);

    platform_set_drvdata(pdev, chip);

    chip->rtc = rtc_device_register("ds2404",
                &pdev->dev, &ds2404_rtc_ops, THIS_MODULE);
    if (IS_ERR(chip->rtc)) {
        retval = PTR_ERR(chip->rtc);
        goto err_io;
    }

    ds2404_enable_osc(&pdev->dev);
    return 0;

err_io:
    chip->ops->unmap_io(chip);
err_chip:
    kfree(chip);
    return retval;
}

static int rtc_remove(struct platform_device *dev)
{
    struct ds2404 *chip = platform_get_drvdata(dev);
    struct rtc_device *rtc = chip->rtc;

    if (rtc)
        rtc_device_unregister(rtc);

    chip->ops->unmap_io(chip);
    kfree(chip);

    return 0;
}

static struct platform_driver rtc_device_driver = {
    .probe  = rtc_probe,
    .remove = rtc_remove,
    .driver = {
        .name   = "ds2404",
        .owner  = THIS_MODULE,
    },
};

static __init int ds2404_init(void)
{
    return platform_driver_register(&rtc_device_driver);
}

static __exit void ds2404_exit(void)
{
    platform_driver_unregister(&rtc_device_driver);
}

module_init(ds2404_init);
module_exit(ds2404_exit);

MODULE_DESCRIPTION("DS2404 RTC");
MODULE_AUTHOR("Sven Schnelle");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:ds2404");