drivers/rtc/rtc-m48t35.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Driver for the SGS-Thomson M48T35 Timekeeper RAM chip
   4  *
   5  * Copyright (C) 2000 Silicon Graphics, Inc.
   6  * Written by Ulf Carlsson (ulfc@engr.sgi.com)
   7  *
   8  * Copyright (C) 2008 Thomas Bogendoerfer
   9  *
  10  * Based on code written by Paul Gortmaker.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/rtc.h>
  15 #include <linux/slab.h>
  16 #include <linux/platform_device.h>
  17 #include <linux/bcd.h>
  18 #include <linux/io.h>
  19 #include <linux/err.h>
  20
  21 struct m48t35_rtc {
  22         u8      pad[0x7ff8];    /* starts at 0x7ff8 */
  23         u8      control;
  24         u8      sec;
  25         u8      min;
  26         u8      hour;
  27         u8      day;
  28         u8      date;
  29         u8      month;
  30         u8      year;
  31 };
  32
  33 #define M48T35_RTC_SET          0x80
  34 #define M48T35_RTC_READ         0x40
  35
  36 struct m48t35_priv {
  37         struct rtc_device *rtc;
  38         struct m48t35_rtc __iomem *reg;
  39         size_t size;
  40         unsigned long baseaddr;
  41         spinlock_t lock;
  42 };
  43
  44 static int m48t35_read_time(struct device *dev, struct rtc_time *tm)
  45 {
  46         struct m48t35_priv *priv = dev_get_drvdata(dev);
  47         u8 control;
  48
  49         /*
  50          * Only the values that we read from the RTC are set. We leave
  51          * tm_wday, tm_yday and tm_isdst untouched. Even though the
  52          * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
  53          * by the RTC when initially set to a non-zero value.
  54          */
  55         spin_lock_irq(&priv->lock);
  56         control = readb(&priv->reg->control);
  57         writeb(control | M48T35_RTC_READ, &priv->reg->control);
  58         tm->tm_sec = readb(&priv->reg->sec);
  59         tm->tm_min = readb(&priv->reg->min);
  60         tm->tm_hour = readb(&priv->reg->hour);
  61         tm->tm_mday = readb(&priv->reg->date);
  62         tm->tm_mon = readb(&priv->reg->month);
  63         tm->tm_year = readb(&priv->reg->year);
  64         writeb(control, &priv->reg->control);
  65         spin_unlock_irq(&priv->lock);
  66
  67         tm->tm_sec = bcd2bin(tm->tm_sec);
  68         tm->tm_min = bcd2bin(tm->tm_min);
  69         tm->tm_hour = bcd2bin(tm->tm_hour);
  70         tm->tm_mday = bcd2bin(tm->tm_mday);
  71         tm->tm_mon = bcd2bin(tm->tm_mon);
  72         tm->tm_year = bcd2bin(tm->tm_year);
  73
  74         /*
  75          * Account for differences between how the RTC uses the values
  76          * and how they are defined in a struct rtc_time;
  77          */
  78         tm->tm_year += 70;
  79         if (tm->tm_year <= 69)
  80                 tm->tm_year += 100;
  81
  82         tm->tm_mon--;
  83         return 0;
  84 }
  85
  86 static int m48t35_set_time(struct device *dev, struct rtc_time *tm)
  87 {
  88         struct m48t35_priv *priv = dev_get_drvdata(dev);
  89         unsigned char mon, day, hrs, min, sec;
  90         unsigned int yrs;
  91         u8 control;
  92
  93         yrs = tm->tm_year + 1900;
  94         mon = tm->tm_mon + 1;   /* tm_mon starts at zero */
  95         day = tm->tm_mday;
  96         hrs = tm->tm_hour;
  97         min = tm->tm_min;
  98         sec = tm->tm_sec;
  99
 100         if (yrs < 1970)
 101                 return -EINVAL;
 102
 103         yrs -= 1970;
 104         if (yrs > 255)    /* They are unsigned */
 105                 return -EINVAL;
 106
 107         if (yrs > 169)
 108                 return -EINVAL;
 109
 110         if (yrs >= 100)
 111                 yrs -= 100;
 112
 113         sec = bin2bcd(sec);
 114         min = bin2bcd(min);
 115         hrs = bin2bcd(hrs);
 116         day = bin2bcd(day);
 117         mon = bin2bcd(mon);
 118         yrs = bin2bcd(yrs);
 119
 120         spin_lock_irq(&priv->lock);
 121         control = readb(&priv->reg->control);
 122         writeb(control | M48T35_RTC_SET, &priv->reg->control);
 123         writeb(yrs, &priv->reg->year);
 124         writeb(mon, &priv->reg->month);
 125         writeb(day, &priv->reg->date);
 126         writeb(hrs, &priv->reg->hour);
 127         writeb(min, &priv->reg->min);
 128         writeb(sec, &priv->reg->sec);
 129         writeb(control, &priv->reg->control);
 130         spin_unlock_irq(&priv->lock);
 131         return 0;
 132 }
 133
 134 static const struct rtc_class_ops m48t35_ops = {
 135         .read_time      = m48t35_read_time,
 136         .set_time       = m48t35_set_time,
 137 };
 138
 139 static int m48t35_probe(struct platform_device *pdev)
 140 {
 141         struct resource *res;
 142         struct m48t35_priv *priv;
 143
 144         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 145         if (!res)
 146                 return -ENODEV;
 147         priv = devm_kzalloc(&pdev->dev, sizeof(struct m48t35_priv), GFP_KERNEL);
 148         if (!priv)
 149                 return -ENOMEM;
 150
 151         priv->size = resource_size(res);
 152         /*
 153          * kludge: remove the #ifndef after ioc3 resource
 154          * conflicts are resolved
 155          */
 156 #ifndef CONFIG_SGI_IP27
 157         if (!devm_request_mem_region(&pdev->dev, res->start, priv->size,
 158                                      pdev->name))
 159                 return -EBUSY;
 160 #endif
 161         priv->baseaddr = res->start;
 162         priv->reg = devm_ioremap(&pdev->dev, priv->baseaddr, priv->size);
 163         if (!priv->reg)
 164                 return -ENOMEM;
 165
 166         spin_lock_init(&priv->lock);
 167
 168         platform_set_drvdata(pdev, priv);
 169
 170         priv->rtc = devm_rtc_device_register(&pdev->dev, "m48t35",
 171                                   &m48t35_ops, THIS_MODULE);
 172         return PTR_ERR_OR_ZERO(priv->rtc);
 173 }
 174
 175 static struct platform_driver m48t35_platform_driver = {
 176         .driver         = {
 177                 .name   = "rtc-m48t35",
 178         },
 179         .probe          = m48t35_probe,
 180 };
 181
 182 module_platform_driver(m48t35_platform_driver);
 183
 184 MODULE_AUTHOR("Thomas Bogendoerfer <tsbogend@alpha.franken.de>");
 185 MODULE_DESCRIPTION("M48T35 RTC driver");
 186 MODULE_LICENSE("GPL");
 187 MODULE_ALIAS("platform:rtc-m48t35");