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
  17 /* Size of NVRAM including both the user-accessible area and the
  18  * secondary register area.
  19  */
  20 #define NVRAM_SIZE 64
  21
  22 /* Flags definitions */
  23 #define SECONDS_CH 0x80
  24 #define HOURS_12   0x40
  25 #define HOURS_PM   0x20
  26 #define CTRL_OSF   0x20
  27
  28 #define TYPE_DS1338 "ds1338"
  29 #define DS1338(obj) OBJECT_CHECK(DS1338State, (obj), TYPE_DS1338)
  30
  31 typedef struct DS1338State {
  32     I2CSlave parent_obj;
  33
  34     int64_t offset;
  35     uint8_t wday_offset;
  36     uint8_t nvram[NVRAM_SIZE];
  37     int32_t ptr;
  38     bool addr_byte;
  39 } DS1338State;
  40
  41 static const VMStateDescription vmstate_ds1338 = {
  42     .name = "ds1338",
  43     .version_id = 2,
  44     .minimum_version_id = 1,
  45     .fields = (VMStateField[]) {
  46         VMSTATE_I2C_SLAVE(parent_obj, DS1338State),
  47         VMSTATE_INT64(offset, DS1338State),
  48         VMSTATE_UINT8_V(wday_offset, DS1338State, 2),
  49         VMSTATE_UINT8_ARRAY(nvram, DS1338State, NVRAM_SIZE),
  50         VMSTATE_INT32(ptr, DS1338State),
  51         VMSTATE_BOOL(addr_byte, DS1338State),
  52         VMSTATE_END_OF_LIST()
  53     }
  54 };
  55
  56 static void capture_current_time(DS1338State *s)
  57 {
  58     /* Capture the current time into the secondary registers
  59      * which will be actually read by the data transfer operation.
  60      */
  61     struct tm now;
  62     qemu_get_timedate(&now, s->offset);
  63     s->nvram[0] = to_bcd(now.tm_sec);
  64     s->nvram[1] = to_bcd(now.tm_min);
  65     if (s->nvram[2] & HOURS_12) {
  66         int tmp = now.tm_hour;
  67         if (tmp % 12 == 0) {
  68             tmp += 12;
  69         }
  70         if (tmp <= 12) {
  71             s->nvram[2] = HOURS_12 | to_bcd(tmp);
  72         } else {
  73             s->nvram[2] = HOURS_12 | HOURS_PM | to_bcd(tmp - 12);
  74         }
  75     } else {
  76         s->nvram[2] = to_bcd(now.tm_hour);
  77     }
  78     s->nvram[3] = (now.tm_wday + s->wday_offset) % 7 + 1;
  79     s->nvram[4] = to_bcd(now.tm_mday);
  80     s->nvram[5] = to_bcd(now.tm_mon + 1);
  81     s->nvram[6] = to_bcd(now.tm_year - 100);
  82 }
  83
  84 static void inc_regptr(DS1338State *s)
  85 {
  86     /* The register pointer wraps around after 0x3F; wraparound
  87      * causes the current time/date to be retransferred into
  88      * the secondary registers.
  89      */
  90     s->ptr = (s->ptr + 1) & (NVRAM_SIZE - 1);
  91     if (!s->ptr) {
  92         capture_current_time(s);
  93     }
  94 }
  95
  96 static void ds1338_event(I2CSlave *i2c, enum i2c_event event)
  97 {
  98     DS1338State *s = DS1338(i2c);
  99
 100     switch (event) {
 101     case I2C_START_RECV:
 102         /* In h/w, capture happens on any START condition, not just a
 103          * START_RECV, but there is no need to actually capture on
 104          * START_SEND, because the guest can't get at that data
 105          * without going through a START_RECV which would overwrite it.
 106          */
 107         capture_current_time(s);
 108         break;
 109     case I2C_START_SEND:
 110         s->addr_byte = true;
 111         break;
 112     default:
 113         break;
 114     }
 115 }
 116
 117 static int ds1338_recv(I2CSlave *i2c)
 118 {
 119     DS1338State *s = DS1338(i2c);
 120     uint8_t res;
 121
 122     res  = s->nvram[s->ptr];
 123     inc_regptr(s);
 124     return res;
 125 }
 126
 127 static int ds1338_send(I2CSlave *i2c, uint8_t data)
 128 {
 129     DS1338State *s = DS1338(i2c);
 130
 131     if (s->addr_byte) {
 132         s->ptr = data & (NVRAM_SIZE - 1);
 133         s->addr_byte = false;
 134         return 0;
 135     }
 136     if (s->ptr < 7) {
 137         /* Time register. */
 138         struct tm now;
 139         qemu_get_timedate(&now, s->offset);
 140         switch(s->ptr) {
 141         case 0:
 142             /* TODO: Implement CH (stop) bit.  */
 143             now.tm_sec = from_bcd(data & 0x7f);
 144             break;
 145         case 1:
 146             now.tm_min = from_bcd(data & 0x7f);
 147             break;
 148         case 2:
 149             if (data & HOURS_12) {
 150                 int tmp = from_bcd(data & (HOURS_PM - 1));
 151                 if (data & HOURS_PM) {
 152                     tmp += 12;
 153                 }
 154                 if (tmp % 12 == 0) {
 155                     tmp -= 12;
 156                 }
 157                 now.tm_hour = tmp;
 158             } else {
 159                 now.tm_hour = from_bcd(data & (HOURS_12 - 1));
 160             }
 161             break;
 162         case 3:
 163             {
 164                 /* The day field is supposed to contain a value in
 165                    the range 1-7. Otherwise behavior is undefined.
 166                  */
 167                 int user_wday = (data & 7) - 1;
 168                 s->wday_offset = (user_wday - now.tm_wday + 7) % 7;
 169             }
 170             break;
 171         case 4:
 172             now.tm_mday = from_bcd(data & 0x3f);
 173             break;
 174         case 5:
 175             now.tm_mon = from_bcd(data & 0x1f) - 1;
 176             break;
 177         case 6:
 178             now.tm_year = from_bcd(data) + 100;
 179             break;
 180         }
 181         s->offset = qemu_timedate_diff(&now);
 182     } else if (s->ptr == 7) {
 183         /* Control register. */
 184
 185         /* Ensure bits 2, 3 and 6 will read back as zero. */
 186         data &= 0xB3;
 187
 188         /* Attempting to write the OSF flag to logic 1 leaves the
 189            value unchanged. */
 190         data = (data & ~CTRL_OSF) | (data & s->nvram[s->ptr] & CTRL_OSF);
 191
 192         s->nvram[s->ptr] = data;
 193     } else {
 194         s->nvram[s->ptr] = data;
 195     }
 196     inc_regptr(s);
 197     return 0;
 198 }
 199
 200 static int ds1338_init(I2CSlave *i2c)
 201 {
 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->init = ds1338_init;
 223     k->event = ds1338_event;
 224     k->recv = ds1338_recv;
 225     k->send = ds1338_send;
 226     dc->reset = ds1338_reset;
 227     dc->vmsd = &vmstate_ds1338;
 228 }
 229
 230 static const TypeInfo ds1338_info = {
 231     .name          = TYPE_DS1338,
 232     .parent        = TYPE_I2C_SLAVE,
 233     .instance_size = sizeof(DS1338State),
 234     .class_init    = ds1338_class_init,
 235 };
 236
 237 static void ds1338_register_types(void)
 238 {
 239     type_register_static(&ds1338_info);
 240 }
 241
 242 type_init(ds1338_register_types)