drivers/rtc/rtc-m48t35.c

   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
  27 struct 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
  42 struct 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
  50 static 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
  92 static 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
 140 static const struct rtc_class_ops m48t35_ops = {
 141         .read_time      = m48t35_read_time,
 142         .set_time       = m48t35_set_time,
 143 };
 144
 145 static 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_ERR_OR_ZERO(priv->rtc);
 179 }
 180
 181 static struct platform_driver m48t35_platform_driver = {
 182         .driver         = {
 183                 .name   = "rtc-m48t35",
 184         },
 185         .probe          = m48t35_probe,
 186 };
 187
 188 module_platform_driver(m48t35_platform_driver);
 189
 190 MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
 191 MODULE_DESCRIPTION("M48T35 RTC driver");
 192 MODULE_LICENSE("GPL");
 193 MODULE_VERSION(DRV_VERSION);
 194 MODULE_ALIAS("platform:rtc-m48t35");