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