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#include <linux/err.h>
  24
  25#define DRV_VERSION             "1.0"
  26
  27struct m48t35_rtc {
  28        u8      pad[0x7ff8];    /* starts at 0x7ff8 */
  29        u8      control;
  30        u8      sec;
  31        u8      min;
  32        u8      hour;
  33        u8      day;
  34        u8      date;
  35        u8      month;
  36        u8      year;
  37};
  38
  39#define M48T35_RTC_SET          0x80
  40#define M48T35_RTC_READ         0x40
  41
  42struct m48t35_priv {
  43        struct rtc_device *rtc;
  44        struct m48t35_rtc __iomem *reg;
  45        size_t size;
  46        unsigned long baseaddr;
  47        spinlock_t lock;
  48};
  49
  50static int m48t35_read_time(struct device *dev, struct rtc_time *tm)
  51{
  52        struct m48t35_priv *priv = dev_get_drvdata(dev);
  53        u8 control;
  54
  55        /*
  56         * Only the values that we read from the RTC are set. We leave
  57         * tm_wday, tm_yday and tm_isdst untouched. Even though the
  58         * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
  59         * by the RTC when initially set to a non-zero value.
  60         */
  61        spin_lock_irq(&priv->lock);
  62        control = readb(&priv->reg->control);
  63        writeb(control | M48T35_RTC_READ, &priv->reg->control);
  64        tm->tm_sec = readb(&priv->reg->sec);
  65        tm->tm_min = readb(&priv->reg->min);
  66        tm->tm_hour = readb(&priv->reg->hour);
  67        tm->tm_mday = readb(&priv->reg->date);
  68        tm->tm_mon = readb(&priv->reg->month);
  69        tm->tm_year = readb(&priv->reg->year);
  70        writeb(control, &priv->reg->control);
  71        spin_unlock_irq(&priv->lock);
  72
  73        tm->tm_sec = bcd2bin(tm->tm_sec);
  74        tm->tm_min = bcd2bin(tm->tm_min);
  75        tm->tm_hour = bcd2bin(tm->tm_hour);
  76        tm->tm_mday = bcd2bin(tm->tm_mday);
  77        tm->tm_mon = bcd2bin(tm->tm_mon);
  78        tm->tm_year = bcd2bin(tm->tm_year);
  79
  80        /*
  81         * Account for differences between how the RTC uses the values
  82         * and how they are defined in a struct rtc_time;
  83         */
  84        tm->tm_year += 70;
  85        if (tm->tm_year <= 69)
  86                tm->tm_year += 100;
  87
  88        tm->tm_mon--;
  89        return rtc_valid_tm(tm);
  90}
  91
  92static int m48t35_set_time(struct device *dev, struct rtc_time *tm)
  93{
  94        struct m48t35_priv *priv = dev_get_drvdata(dev);
  95        unsigned char mon, day, hrs, min, sec;
  96        unsigned int yrs;
  97        u8 control;
  98
  99        yrs = tm->tm_year + 1900;
 100        mon = tm->tm_mon + 1;   /* tm_mon starts at zero */
 101        day = tm->tm_mday;
 102        hrs = tm->tm_hour;
 103        min = tm->tm_min;
 104        sec = tm->tm_sec;
 105
 106        if (yrs < 1970)
 107                return -EINVAL;
 108
 109        yrs -= 1970;
 110        if (yrs > 255)    /* They are unsigned */
 111                return -EINVAL;
 112
 113        if (yrs > 169)
 114                return -EINVAL;
 115
 116        if (yrs >= 100)
 117                yrs -= 100;
 118
 119        sec = bin2bcd(sec);
 120        min = bin2bcd(min);
 121        hrs = bin2bcd(hrs);
 122        day = bin2bcd(day);
 123        mon = bin2bcd(mon);
 124        yrs = bin2bcd(yrs);
 125
 126        spin_lock_irq(&priv->lock);
 127        control = readb(&priv->reg->control);
 128        writeb(control | M48T35_RTC_SET, &priv->reg->control);
 129        writeb(yrs, &priv->reg->year);
 130        writeb(mon, &priv->reg->month);
 131        writeb(day, &priv->reg->date);
 132        writeb(hrs, &priv->reg->hour);
 133        writeb(min, &priv->reg->min);
 134        writeb(sec, &priv->reg->sec);
 135        writeb(control, &priv->reg->control);
 136        spin_unlock_irq(&priv->lock);
 137        return 0;
 138}
 139
 140static const struct rtc_class_ops m48t35_ops = {
 141        .read_time      = m48t35_read_time,
 142        .set_time       = m48t35_set_time,
 143};
 144
 145static int m48t35_probe(struct platform_device *pdev)
 146{
 147        struct resource *res;
 148        struct m48t35_priv *priv;
 149
 150        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 151        if (!res)
 152                return -ENODEV;
 153        priv = devm_kzalloc(&pdev->dev, sizeof(struct m48t35_priv), GFP_KERNEL);
 154        if (!priv)
 155                return -ENOMEM;
 156
 157        priv->size = resource_size(res);
 158        /*
 159         * kludge: remove the #ifndef after ioc3 resource
 160         * conflicts are resolved
 161         */
 162#ifndef CONFIG_SGI_IP27
 163        if (!devm_request_mem_region(&pdev->dev, res->start, priv->size,
 164                                     pdev->name))
 165                return -EBUSY;
 166#endif
 167        priv->baseaddr = res->start;
 168        priv->reg = devm_ioremap(&pdev->dev, priv->baseaddr, priv->size);
 169        if (!priv->reg)
 170                return -ENOMEM;
 171
 172        spin_lock_init(&priv->lock);
 173
 174        platform_set_drvdata(pdev, priv);
 175
 176        priv->rtc = devm_rtc_device_register(&pdev->dev, "m48t35",
 177                                  &m48t35_ops, THIS_MODULE);
 178        return PTR_RET(priv->rtc);
 179}
 180
 181static struct platform_driver m48t35_platform_driver = {
 182        .driver         = {
 183                .name   = "rtc-m48t35",
 184                .owner  = THIS_MODULE,
 185        },
 186        .probe          = m48t35_probe,
 187};
 188
 189module_platform_driver(m48t35_platform_driver);
 190
 191MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
 192MODULE_DESCRIPTION("M48T35 RTC driver");
 193MODULE_LICENSE("GPL");
 194MODULE_VERSION(DRV_VERSION);
 195MODULE_ALIAS("platform:rtc-m48t35");
 196
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