linux/drivers/rtc/rtc-m48t35.c
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   1/*
   2 * Driver for the SGS-Thomson M48T35 Timekeeper RAM chip
   3 *
   4 * Copyright (C) 2000 Silicon Graphics, Inc.
   5 * Written by Ulf Carlsson (ulfc@engr.sgi.com)
   6 *
   7 * Copyright (C) 2008 Thomas Bogendoerfer
   8 *
   9 * Based on code written by Paul Gortmaker.
  10 *
  11 * This program is free software; you can redistribute it and/or modify it
  12 * under the terms of the GNU General Public License as published by the
  13 * Free Software Foundation; either version 2 of the License, or (at your
  14 * option) any later version.
  15 */
  16
  17#include <linux/module.h>
  18#include <linux/rtc.h>
  19#include <linux/slab.h>
  20#include <linux/platform_device.h>
  21#include <linux/bcd.h>
  22#include <linux/io.h>
  23
  24#define DRV_VERSION             "1.0"
  25
  26struct m48t35_rtc {
  27        u8      pad[0x7ff8];    /* starts at 0x7ff8 */
  28        u8      control;
  29        u8      sec;
  30        u8      min;
  31        u8      hour;
  32        u8      day;
  33        u8      date;
  34        u8      month;
  35        u8      year;
  36};
  37
  38#define M48T35_RTC_SET          0x80
  39#define M48T35_RTC_READ         0x40
  40
  41struct m48t35_priv {
  42        struct rtc_device *rtc;
  43        struct m48t35_rtc __iomem *reg;
  44        size_t size;
  45        unsigned long baseaddr;
  46        spinlock_t lock;
  47};
  48
  49static int m48t35_read_time(struct device *dev, struct rtc_time *tm)
  50{
  51        struct m48t35_priv *priv = dev_get_drvdata(dev);
  52        u8 control;
  53
  54        /*
  55         * Only the values that we read from the RTC are set. We leave
  56         * tm_wday, tm_yday and tm_isdst untouched. Even though the
  57         * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
  58         * by the RTC when initially set to a non-zero value.
  59         */
  60        spin_lock_irq(&priv->lock);
  61        control = readb(&priv->reg->control);
  62        writeb(control | M48T35_RTC_READ, &priv->reg->control);
  63        tm->tm_sec = readb(&priv->reg->sec);
  64        tm->tm_min = readb(&priv->reg->min);
  65        tm->tm_hour = readb(&priv->reg->hour);
  66        tm->tm_mday = readb(&priv->reg->date);
  67        tm->tm_mon = readb(&priv->reg->month);
  68        tm->tm_year = readb(&priv->reg->year);
  69        writeb(control, &priv->reg->control);
  70        spin_unlock_irq(&priv->lock);
  71
  72        tm->tm_sec = bcd2bin(tm->tm_sec);
  73        tm->tm_min = bcd2bin(tm->tm_min);
  74        tm->tm_hour = bcd2bin(tm->tm_hour);
  75        tm->tm_mday = bcd2bin(tm->tm_mday);
  76        tm->tm_mon = bcd2bin(tm->tm_mon);
  77        tm->tm_year = bcd2bin(tm->tm_year);
  78
  79        /*
  80         * Account for differences between how the RTC uses the values
  81         * and how they are defined in a struct rtc_time;
  82         */
  83        tm->tm_year += 70;
  84        if (tm->tm_year <= 69)
  85                tm->tm_year += 100;
  86
  87        tm->tm_mon--;
  88        return rtc_valid_tm(tm);
  89}
  90
  91static int m48t35_set_time(struct device *dev, struct rtc_time *tm)
  92{
  93        struct m48t35_priv *priv = dev_get_drvdata(dev);
  94        unsigned char mon, day, hrs, min, sec;
  95        unsigned int yrs;
  96        u8 control;
  97
  98        yrs = tm->tm_year + 1900;
  99        mon = tm->tm_mon + 1;   /* tm_mon starts at zero */
 100        day = tm->tm_mday;
 101        hrs = tm->tm_hour;
 102        min = tm->tm_min;
 103        sec = tm->tm_sec;
 104
 105        if (yrs < 1970)
 106                return -EINVAL;
 107
 108        yrs -= 1970;
 109        if (yrs > 255)    /* They are unsigned */
 110                return -EINVAL;
 111
 112        if (yrs > 169)
 113                return -EINVAL;
 114
 115        if (yrs >= 100)
 116                yrs -= 100;
 117
 118        sec = bin2bcd(sec);
 119        min = bin2bcd(min);
 120        hrs = bin2bcd(hrs);
 121        day = bin2bcd(day);
 122        mon = bin2bcd(mon);
 123        yrs = bin2bcd(yrs);
 124
 125        spin_lock_irq(&priv->lock);
 126        control = readb(&priv->reg->control);
 127        writeb(control | M48T35_RTC_SET, &priv->reg->control);
 128        writeb(yrs, &priv->reg->year);
 129        writeb(mon, &priv->reg->month);
 130        writeb(day, &priv->reg->date);
 131        writeb(hrs, &priv->reg->hour);
 132        writeb(min, &priv->reg->min);
 133        writeb(sec, &priv->reg->sec);
 134        writeb(control, &priv->reg->control);
 135        spin_unlock_irq(&priv->lock);
 136        return 0;
 137}
 138
 139static const struct rtc_class_ops m48t35_ops = {
 140        .read_time      = m48t35_read_time,
 141        .set_time       = m48t35_set_time,
 142};
 143
 144static int m48t35_probe(struct platform_device *pdev)
 145{
 146        struct resource *res;
 147        struct m48t35_priv *priv;
 148
 149        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 150        if (!res)
 151                return -ENODEV;
 152        priv = devm_kzalloc(&pdev->dev, sizeof(struct m48t35_priv), GFP_KERNEL);
 153        if (!priv)
 154                return -ENOMEM;
 155
 156        priv->size = resource_size(res);
 157        /*
 158         * kludge: remove the #ifndef after ioc3 resource
 159         * conflicts are resolved
 160         */
 161#ifndef CONFIG_SGI_IP27
 162        if (!devm_request_mem_region(&pdev->dev, res->start, priv->size,
 163                                     pdev->name))
 164                return -EBUSY;
 165#endif
 166        priv->baseaddr = res->start;
 167        priv->reg = devm_ioremap(&pdev->dev, priv->baseaddr, priv->size);
 168        if (!priv->reg)
 169                return -ENOMEM;
 170
 171        spin_lock_init(&priv->lock);
 172
 173        platform_set_drvdata(pdev, priv);
 174
 175        priv->rtc = devm_rtc_device_register(&pdev->dev, "m48t35",
 176                                  &m48t35_ops, THIS_MODULE);
 177        if (IS_ERR(priv->rtc))
 178                return PTR_ERR(priv->rtc);
 179
 180        return 0;
 181}
 182
 183static int m48t35_remove(struct platform_device *pdev)
 184{
 185        return 0;
 186}
 187
 188static struct platform_driver m48t35_platform_driver = {
 189        .driver         = {
 190                .name   = "rtc-m48t35",
 191                .owner  = THIS_MODULE,
 192        },
 193        .probe          = m48t35_probe,
 194        .remove         = m48t35_remove,
 195};
 196
 197module_platform_driver(m48t35_platform_driver);
 198
 199MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
 200MODULE_DESCRIPTION("M48T35 RTC driver");
 201MODULE_LICENSE("GPL");
 202MODULE_VERSION(DRV_VERSION);
 203MODULE_ALIAS("platform:rtc-m48t35");
 204
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