hw/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 "hw/i2c/i2c.h"
  14
  15 /* Size of NVRAM including both the user-accessible area and the
  16  * secondary register area.
  17  */
  18 #define NVRAM_SIZE 64
  19
  20 /* Flags definitions */
  21 #define SECONDS_CH 0x80
  22 #define HOURS_12   0x40
  23 #define HOURS_PM   0x20
  24 #define CTRL_OSF   0x20
  25
  26 typedef struct {
  27     I2CSlave i2c;
  28     int64_t offset;
  29     uint8_t wday_offset;
  30     uint8_t nvram[NVRAM_SIZE];
  31     int32_t ptr;
  32     bool addr_byte;
  33 } DS1338State;
  34
  35 static const VMStateDescription vmstate_ds1338 = {
  36     .name = "ds1338",
  37     .version_id = 2,
  38     .minimum_version_id = 1,
  39     .minimum_version_id_old = 1,
  40     .fields = (VMStateField[]) {
  41         VMSTATE_I2C_SLAVE(i2c, DS1338State),
  42         VMSTATE_INT64(offset, DS1338State),
  43         VMSTATE_UINT8_V(wday_offset, DS1338State, 2),
  44         VMSTATE_UINT8_ARRAY(nvram, DS1338State, NVRAM_SIZE),
  45         VMSTATE_INT32(ptr, DS1338State),
  46         VMSTATE_BOOL(addr_byte, DS1338State),
  47         VMSTATE_END_OF_LIST()
  48     }
  49 };
  50
  51 static void capture_current_time(DS1338State *s)
  52 {
  53     /* Capture the current time into the secondary registers
  54      * which will be actually read by the data transfer operation.
  55      */
  56     struct tm now;
  57     qemu_get_timedate(&now, s->offset);
  58     s->nvram[0] = to_bcd(now.tm_sec);
  59     s->nvram[1] = to_bcd(now.tm_min);
  60     if (s->nvram[2] & HOURS_12) {
  61         int tmp = now.tm_hour;
  62         if (tmp % 12 == 0) {
  63             tmp += 12;
  64         }
  65         if (tmp <= 12) {
  66             s->nvram[2] = HOURS_12 | to_bcd(tmp);
  67         } else {
  68             s->nvram[2] = HOURS_12 | HOURS_PM | to_bcd(tmp - 12);
  69         }
  70     } else {
  71         s->nvram[2] = to_bcd(now.tm_hour);
  72     }
  73     s->nvram[3] = (now.tm_wday + s->wday_offset) % 7 + 1;
  74     s->nvram[4] = to_bcd(now.tm_mday);
  75     s->nvram[5] = to_bcd(now.tm_mon + 1);
  76     s->nvram[6] = to_bcd(now.tm_year - 100);
  77 }
  78
  79 static void inc_regptr(DS1338State *s)
  80 {
  81     /* The register pointer wraps around after 0x3F; wraparound
  82      * causes the current time/date to be retransferred into
  83      * the secondary registers.
  84      */
  85     s->ptr = (s->ptr + 1) & (NVRAM_SIZE - 1);
  86     if (!s->ptr) {
  87         capture_current_time(s);
  88     }
  89 }
  90
  91 static void ds1338_event(I2CSlave *i2c, enum i2c_event event)
  92 {
  93     DS1338State *s = FROM_I2C_SLAVE(DS1338State, i2c);
  94
  95     switch (event) {
  96     case I2C_START_RECV:
  97         /* In h/w, capture happens on any START condition, not just a
  98          * START_RECV, but there is no need to actually capture on
  99          * START_SEND, because the guest can't get at that data
 100          * without going through a START_RECV which would overwrite it.
 101          */
 102         capture_current_time(s);
 103         break;
 104     case I2C_START_SEND:
 105         s->addr_byte = true;
 106         break;
 107     default:
 108         break;
 109     }
 110 }
 111
 112 static int ds1338_recv(I2CSlave *i2c)
 113 {
 114     DS1338State *s = FROM_I2C_SLAVE(DS1338State, i2c);
 115     uint8_t res;
 116
 117     res  = s->nvram[s->ptr];
 118     inc_regptr(s);
 119     return res;
 120 }
 121
 122 static int ds1338_send(I2CSlave *i2c, uint8_t data)
 123 {
 124     DS1338State *s = FROM_I2C_SLAVE(DS1338State, i2c);
 125     if (s->addr_byte) {
 126         s->ptr = data & (NVRAM_SIZE - 1);
 127         s->addr_byte = false;
 128         return 0;
 129     }
 130     if (s->ptr < 7) {
 131         /* Time register. */
 132         struct tm now;
 133         qemu_get_timedate(&now, s->offset);
 134         switch(s->ptr) {
 135         case 0:
 136             /* TODO: Implement CH (stop) bit.  */
 137             now.tm_sec = from_bcd(data & 0x7f);
 138             break;
 139         case 1:
 140             now.tm_min = from_bcd(data & 0x7f);
 141             break;
 142         case 2:
 143             if (data & HOURS_12) {
 144                 int tmp = from_bcd(data & (HOURS_PM - 1));
 145                 if (data & HOURS_PM) {
 146                     tmp += 12;
 147                 }
 148                 if (tmp % 12 == 0) {
 149                     tmp -= 12;
 150                 }
 151                 now.tm_hour = tmp;
 152             } else {
 153                 now.tm_hour = from_bcd(data & (HOURS_12 - 1));
 154             }
 155             break;
 156         case 3:
 157             {
 158                 /* The day field is supposed to contain a value in
 159                    the range 1-7. Otherwise behavior is undefined.
 160                  */
 161                 int user_wday = (data & 7) - 1;
 162                 s->wday_offset = (user_wday - now.tm_wday + 7) % 7;
 163             }
 164             break;
 165         case 4:
 166             now.tm_mday = from_bcd(data & 0x3f);
 167             break;
 168         case 5:
 169             now.tm_mon = from_bcd(data & 0x1f) - 1;
 170             break;
 171         case 6:
 172             now.tm_year = from_bcd(data) + 100;
 173             break;
 174         }
 175         s->offset = qemu_timedate_diff(&now);
 176     } else if (s->ptr == 7) {
 177         /* Control register. */
 178
 179         /* Ensure bits 2, 3 and 6 will read back as zero. */
 180         data &= 0xB3;
 181
 182         /* Attempting to write the OSF flag to logic 1 leaves the
 183            value unchanged. */
 184         data = (data & ~CTRL_OSF) | (data & s->nvram[s->ptr] & CTRL_OSF);
 185
 186         s->nvram[s->ptr] = data;
 187     } else {
 188         s->nvram[s->ptr] = data;
 189     }
 190     inc_regptr(s);
 191     return 0;
 192 }
 193
 194 static int ds1338_init(I2CSlave *i2c)
 195 {
 196     return 0;
 197 }
 198
 199 static void ds1338_reset(DeviceState *dev)
 200 {
 201     DS1338State *s = FROM_I2C_SLAVE(DS1338State, I2C_SLAVE(dev));
 202
 203     /* The clock is running and synchronized with the host */
 204     s->offset = 0;
 205     s->wday_offset = 0;
 206     memset(s->nvram, 0, NVRAM_SIZE);
 207     s->ptr = 0;
 208     s->addr_byte = false;
 209 }
 210
 211 static void ds1338_class_init(ObjectClass *klass, void *data)
 212 {
 213     DeviceClass *dc = DEVICE_CLASS(klass);
 214     I2CSlaveClass *k = I2C_SLAVE_CLASS(klass);
 215
 216     k->init = ds1338_init;
 217     k->event = ds1338_event;
 218     k->recv = ds1338_recv;
 219     k->send = ds1338_send;
 220     dc->reset = ds1338_reset;
 221     dc->vmsd = &vmstate_ds1338;
 222 }
 223
 224 static const TypeInfo ds1338_info = {
 225     .name          = "ds1338",
 226     .parent        = TYPE_I2C_SLAVE,
 227     .instance_size = sizeof(DS1338State),
 228     .class_init    = ds1338_class_init,
 229 };
 230
 231 static void ds1338_register_types(void)
 232 {
 233     type_register_static(&ds1338_info);
 234 }
 235
 236 type_init(ds1338_register_types)