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
  24 #define DRV_VERSION             "1.0"
  25
  26 struct 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
  41 struct 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
  49 static 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
  91 static 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
 139 static const struct rtc_class_ops m48t35_ops = {
 140         .read_time      = m48t35_read_time,
 141         .set_time       = m48t35_set_time,
 142 };
 143
 144 static 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
 183 static int m48t35_remove(struct platform_device *pdev)
 184 {
 185         return 0;
 186 }
 187
 188 static 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
 197 module_platform_driver(m48t35_platform_driver);
 198
 199 MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
 200 MODULE_DESCRIPTION("M48T35 RTC driver");
 201 MODULE_LICENSE("GPL");
 202 MODULE_VERSION(DRV_VERSION);
 203 MODULE_ALIAS("platform:rtc-m48t35");