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