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