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 "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 #define TYPE_DS1338 "ds1338"
  27 #define DS1338(obj) OBJECT_CHECK(DS1338State, (obj), TYPE_DS1338)
  28
  29 typedef struct DS1338State {
  30     I2CSlave parent_obj;
  31
  32     int64_t offset;
  33     uint8_t wday_offset;
  34     uint8_t nvram[NVRAM_SIZE];
  35     int32_t ptr;
  36     bool addr_byte;
  37 } DS1338State;
  38
  39 static const VMStateDescription vmstate_ds1338 = {
  40     .name = "ds1338",
  41     .version_id = 2,
  42     .minimum_version_id = 1,
  43     .fields = (VMStateField[]) {
  44         VMSTATE_I2C_SLAVE(parent_obj, DS1338State),
  45         VMSTATE_INT64(offset, DS1338State),
  46         VMSTATE_UINT8_V(wday_offset, DS1338State, 2),
  47         VMSTATE_UINT8_ARRAY(nvram, DS1338State, NVRAM_SIZE),
  48         VMSTATE_INT32(ptr, DS1338State),
  49         VMSTATE_BOOL(addr_byte, DS1338State),
  50         VMSTATE_END_OF_LIST()
  51     }
  52 };
  53
  54 static void capture_current_time(DS1338State *s)
  55 {
  56     /* Capture the current time into the secondary registers
  57      * which will be actually read by the data transfer operation.
  58      */
  59     struct tm now;
  60     qemu_get_timedate(&now, s->offset);
  61     s->nvram[0] = to_bcd(now.tm_sec);
  62     s->nvram[1] = to_bcd(now.tm_min);
  63     if (s->nvram[2] & HOURS_12) {
  64         int tmp = now.tm_hour;
  65         if (tmp % 12 == 0) {
  66             tmp += 12;
  67         }
  68         if (tmp <= 12) {
  69             s->nvram[2] = HOURS_12 | to_bcd(tmp);
  70         } else {
  71             s->nvram[2] = HOURS_12 | HOURS_PM | to_bcd(tmp - 12);
  72         }
  73     } else {
  74         s->nvram[2] = to_bcd(now.tm_hour);
  75     }
  76     s->nvram[3] = (now.tm_wday + s->wday_offset) % 7 + 1;
  77     s->nvram[4] = to_bcd(now.tm_mday);
  78     s->nvram[5] = to_bcd(now.tm_mon + 1);
  79     s->nvram[6] = to_bcd(now.tm_year - 100);
  80 }
  81
  82 static void inc_regptr(DS1338State *s)
  83 {
  84     /* The register pointer wraps around after 0x3F; wraparound
  85      * causes the current time/date to be retransferred into
  86      * the secondary registers.
  87      */
  88     s->ptr = (s->ptr + 1) & (NVRAM_SIZE - 1);
  89     if (!s->ptr) {
  90         capture_current_time(s);
  91     }
  92 }
  93
  94 static void ds1338_event(I2CSlave *i2c, enum i2c_event event)
  95 {
  96     DS1338State *s = DS1338(i2c);
  97
  98     switch (event) {
  99     case I2C_START_RECV:
 100         /* In h/w, capture happens on any START condition, not just a
 101          * START_RECV, but there is no need to actually capture on
 102          * START_SEND, because the guest can't get at that data
 103          * without going through a START_RECV which would overwrite it.
 104          */
 105         capture_current_time(s);
 106         break;
 107     case I2C_START_SEND:
 108         s->addr_byte = true;
 109         break;
 110     default:
 111         break;
 112     }
 113 }
 114
 115 static int ds1338_recv(I2CSlave *i2c)
 116 {
 117     DS1338State *s = DS1338(i2c);
 118     uint8_t res;
 119
 120     res  = s->nvram[s->ptr];
 121     inc_regptr(s);
 122     return res;
 123 }
 124
 125 static int ds1338_send(I2CSlave *i2c, uint8_t data)
 126 {
 127     DS1338State *s = DS1338(i2c);
 128
 129     if (s->addr_byte) {
 130         s->ptr = data & (NVRAM_SIZE - 1);
 131         s->addr_byte = false;
 132         return 0;
 133     }
 134     if (s->ptr < 7) {
 135         /* Time register. */
 136         struct tm now;
 137         qemu_get_timedate(&now, s->offset);
 138         switch(s->ptr) {
 139         case 0:
 140             /* TODO: Implement CH (stop) bit.  */
 141             now.tm_sec = from_bcd(data & 0x7f);
 142             break;
 143         case 1:
 144             now.tm_min = from_bcd(data & 0x7f);
 145             break;
 146         case 2:
 147             if (data & HOURS_12) {
 148                 int tmp = from_bcd(data & (HOURS_PM - 1));
 149                 if (data & HOURS_PM) {
 150                     tmp += 12;
 151                 }
 152                 if (tmp % 12 == 0) {
 153                     tmp -= 12;
 154                 }
 155                 now.tm_hour = tmp;
 156             } else {
 157                 now.tm_hour = from_bcd(data & (HOURS_12 - 1));
 158             }
 159             break;
 160         case 3:
 161             {
 162                 /* The day field is supposed to contain a value in
 163                    the range 1-7. Otherwise behavior is undefined.
 164                  */
 165                 int user_wday = (data & 7) - 1;
 166                 s->wday_offset = (user_wday - now.tm_wday + 7) % 7;
 167             }
 168             break;
 169         case 4:
 170             now.tm_mday = from_bcd(data & 0x3f);
 171             break;
 172         case 5:
 173             now.tm_mon = from_bcd(data & 0x1f) - 1;
 174             break;
 175         case 6:
 176             now.tm_year = from_bcd(data) + 100;
 177             break;
 178         }
 179         s->offset = qemu_timedate_diff(&now);
 180     } else if (s->ptr == 7) {
 181         /* Control register. */
 182
 183         /* Ensure bits 2, 3 and 6 will read back as zero. */
 184         data &= 0xB3;
 185
 186         /* Attempting to write the OSF flag to logic 1 leaves the
 187            value unchanged. */
 188         data = (data & ~CTRL_OSF) | (data & s->nvram[s->ptr] & CTRL_OSF);
 189
 190         s->nvram[s->ptr] = data;
 191     } else {
 192         s->nvram[s->ptr] = data;
 193     }
 194     inc_regptr(s);
 195     return 0;
 196 }
 197
 198 static int ds1338_init(I2CSlave *i2c)
 199 {
 200     return 0;
 201 }
 202
 203 static void ds1338_reset(DeviceState *dev)
 204 {
 205     DS1338State *s = DS1338(dev);
 206
 207     /* The clock is running and synchronized with the host */
 208     s->offset = 0;
 209     s->wday_offset = 0;
 210     memset(s->nvram, 0, NVRAM_SIZE);
 211     s->ptr = 0;
 212     s->addr_byte = false;
 213 }
 214
 215 static void ds1338_class_init(ObjectClass *klass, void *data)
 216 {
 217     DeviceClass *dc = DEVICE_CLASS(klass);
 218     I2CSlaveClass *k = I2C_SLAVE_CLASS(klass);
 219
 220     k->init = ds1338_init;
 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)