hw/timer/ds1338.c

   1 /*
   2  * MAXIM DS1338 I2C RTC+NVRAM
   3  *
   4  * Copyright (c) 2009 CodeSourcery.
   5  * Written by Paul Brook
   6  *
   7  * This code is licensed under the GNU GPL v2.
   8  *
   9  * Contributions after 2012-01-13 are licensed under the terms of the
  10  * GNU GPL, version 2 or (at your option) any later version.
  11  */
  12
  13 #include "qemu/osdep.h"
  14 #include "qemu-common.h"
  15 #include "hw/i2c/i2c.h"
  16 #include "qemu/bcd.h"
  17 #include "qemu/module.h"
  18
  19 /* Size of NVRAM including both the user-accessible area and the
  20  * secondary register area.
  21  */
  22 #define NVRAM_SIZE 64
  23
  24 /* Flags definitions */
  25 #define SECONDS_CH 0x80
  26 #define HOURS_12   0x40
  27 #define HOURS_PM   0x20
  28 #define CTRL_OSF   0x20
  29
  30 #define TYPE_DS1338 "ds1338"
  31 #define DS1338(obj) OBJECT_CHECK(DS1338State, (obj), TYPE_DS1338)
  32
  33 typedef struct DS1338State {
  34     I2CSlave parent_obj;
  35
  36     int64_t offset;
  37     uint8_t wday_offset;
  38     uint8_t nvram[NVRAM_SIZE];
  39     int32_t ptr;
  40     bool addr_byte;
  41 } DS1338State;
  42
  43 static const VMStateDescription vmstate_ds1338 = {
  44     .name = "ds1338",
  45     .version_id = 2,
  46     .minimum_version_id = 1,
  47     .fields = (VMStateField[]) {
  48         VMSTATE_I2C_SLAVE(parent_obj, DS1338State),
  49         VMSTATE_INT64(offset, DS1338State),
  50         VMSTATE_UINT8_V(wday_offset, DS1338State, 2),
  51         VMSTATE_UINT8_ARRAY(nvram, DS1338State, NVRAM_SIZE),
  52         VMSTATE_INT32(ptr, DS1338State),
  53         VMSTATE_BOOL(addr_byte, DS1338State),
  54         VMSTATE_END_OF_LIST()
  55     }
  56 };
  57
  58 static void capture_current_time(DS1338State *s)
  59 {
  60     /* Capture the current time into the secondary registers
  61      * which will be actually read by the data transfer operation.
  62      */
  63     struct tm now;
  64     qemu_get_timedate(&now, s->offset);
  65     s->nvram[0] = to_bcd(now.tm_sec);
  66     s->nvram[1] = to_bcd(now.tm_min);
  67     if (s->nvram[2] & HOURS_12) {
  68         int tmp = now.tm_hour;
  69         if (tmp % 12 == 0) {
  70             tmp += 12;
  71         }
  72         if (tmp <= 12) {
  73             s->nvram[2] = HOURS_12 | to_bcd(tmp);
  74         } else {
  75             s->nvram[2] = HOURS_12 | HOURS_PM | to_bcd(tmp - 12);
  76         }
  77     } else {
  78         s->nvram[2] = to_bcd(now.tm_hour);
  79     }
  80     s->nvram[3] = (now.tm_wday + s->wday_offset) % 7 + 1;
  81     s->nvram[4] = to_bcd(now.tm_mday);
  82     s->nvram[5] = to_bcd(now.tm_mon + 1);
  83     s->nvram[6] = to_bcd(now.tm_year - 100);
  84 }
  85
  86 static void inc_regptr(DS1338State *s)
  87 {
  88     /* The register pointer wraps around after 0x3F; wraparound
  89      * causes the current time/date to be retransferred into
  90      * the secondary registers.
  91      */
  92     s->ptr = (s->ptr + 1) & (NVRAM_SIZE - 1);
  93     if (!s->ptr) {
  94         capture_current_time(s);
  95     }
  96 }
  97
  98 static int ds1338_event(I2CSlave *i2c, enum i2c_event event)
  99 {
 100     DS1338State *s = DS1338(i2c);
 101
 102     switch (event) {
 103     case I2C_START_RECV:
 104         /* In h/w, capture happens on any START condition, not just a
 105          * START_RECV, but there is no need to actually capture on
 106          * START_SEND, because the guest can't get at that data
 107          * without going through a START_RECV which would overwrite it.
 108          */
 109         capture_current_time(s);
 110         break;
 111     case I2C_START_SEND:
 112         s->addr_byte = true;
 113         break;
 114     default:
 115         break;
 116     }
 117
 118     return 0;
 119 }
 120
 121 static uint8_t ds1338_recv(I2CSlave *i2c)
 122 {
 123     DS1338State *s = DS1338(i2c);
 124     uint8_t res;
 125
 126     res  = s->nvram[s->ptr];
 127     inc_regptr(s);
 128     return res;
 129 }
 130
 131 static int ds1338_send(I2CSlave *i2c, uint8_t data)
 132 {
 133     DS1338State *s = DS1338(i2c);
 134
 135     if (s->addr_byte) {
 136         s->ptr = data & (NVRAM_SIZE - 1);
 137         s->addr_byte = false;
 138         return 0;
 139     }
 140     if (s->ptr < 7) {
 141         /* Time register. */
 142         struct tm now;
 143         qemu_get_timedate(&now, s->offset);
 144         switch(s->ptr) {
 145         case 0:
 146             /* TODO: Implement CH (stop) bit.  */
 147             now.tm_sec = from_bcd(data & 0x7f);
 148             break;
 149         case 1:
 150             now.tm_min = from_bcd(data & 0x7f);
 151             break;
 152         case 2:
 153             if (data & HOURS_12) {
 154                 int tmp = from_bcd(data & (HOURS_PM - 1));
 155                 if (data & HOURS_PM) {
 156                     tmp += 12;
 157                 }
 158                 if (tmp % 12 == 0) {
 159                     tmp -= 12;
 160                 }
 161                 now.tm_hour = tmp;
 162             } else {
 163                 now.tm_hour = from_bcd(data & (HOURS_12 - 1));
 164             }
 165             break;
 166         case 3:
 167             {
 168                 /* The day field is supposed to contain a value in
 169                    the range 1-7. Otherwise behavior is undefined.
 170                  */
 171                 int user_wday = (data & 7) - 1;
 172                 s->wday_offset = (user_wday - now.tm_wday + 7) % 7;
 173             }
 174             break;
 175         case 4:
 176             now.tm_mday = from_bcd(data & 0x3f);
 177             break;
 178         case 5:
 179             now.tm_mon = from_bcd(data & 0x1f) - 1;
 180             break;
 181         case 6:
 182             now.tm_year = from_bcd(data) + 100;
 183             break;
 184         }
 185         s->offset = qemu_timedate_diff(&now);
 186     } else if (s->ptr == 7) {
 187         /* Control register. */
 188
 189         /* Ensure bits 2, 3 and 6 will read back as zero. */
 190         data &= 0xB3;
 191
 192         /* Attempting to write the OSF flag to logic 1 leaves the
 193            value unchanged. */
 194         data = (data & ~CTRL_OSF) | (data & s->nvram[s->ptr] & CTRL_OSF);
 195
 196         s->nvram[s->ptr] = data;
 197     } else {
 198         s->nvram[s->ptr] = data;
 199     }
 200     inc_regptr(s);
 201     return 0;
 202 }
 203
 204 static void ds1338_reset(DeviceState *dev)
 205 {
 206     DS1338State *s = DS1338(dev);
 207
 208     /* The clock is running and synchronized with the host */
 209     s->offset = 0;
 210     s->wday_offset = 0;
 211     memset(s->nvram, 0, NVRAM_SIZE);
 212     s->ptr = 0;
 213     s->addr_byte = false;
 214 }
 215
 216 static void ds1338_class_init(ObjectClass *klass, void *data)
 217 {
 218     DeviceClass *dc = DEVICE_CLASS(klass);
 219     I2CSlaveClass *k = I2C_SLAVE_CLASS(klass);
 220
 221     k->event = ds1338_event;
 222     k->recv = ds1338_recv;
 223     k->send = ds1338_send;
 224     dc->reset = ds1338_reset;
 225     dc->vmsd = &vmstate_ds1338;
 226 }
 227
 228 static const TypeInfo ds1338_info = {
 229     .name          = TYPE_DS1338,
 230     .parent        = TYPE_I2C_SLAVE,
 231     .instance_size = sizeof(DS1338State),
 232     .class_init    = ds1338_class_init,
 233 };
 234
 235 static void ds1338_register_types(void)
 236 {
 237     type_register_static(&ds1338_info);
 238 }
 239
 240 type_init(ds1338_register_types)