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 #include "qom/object.h"
  20
  21 /* Size of NVRAM including both the user-accessible area and the
  22  * secondary register area.
  23  */
  24 #define NVRAM_SIZE 64
  25
  26 /* Flags definitions */
  27 #define SECONDS_CH 0x80
  28 #define HOURS_12   0x40
  29 #define HOURS_PM   0x20
  30 #define CTRL_OSF   0x20
  31
  32 #define TYPE_DS1338 "ds1338"
  33 typedef struct DS1338State DS1338State;
  34 DECLARE_INSTANCE_CHECKER(DS1338State, DS1338,
  35                          TYPE_DS1338)
  36
  37 struct DS1338State {
  38     I2CSlave parent_obj;
  39
  40     int64_t offset;
  41     uint8_t wday_offset;
  42     uint8_t nvram[NVRAM_SIZE];
  43     int32_t ptr;
  44     bool addr_byte;
  45 };
  46
  47 static const VMStateDescription vmstate_ds1338 = {
  48     .name = "ds1338",
  49     .version_id = 2,
  50     .minimum_version_id = 1,
  51     .fields = (VMStateField[]) {
  52         VMSTATE_I2C_SLAVE(parent_obj, DS1338State),
  53         VMSTATE_INT64(offset, DS1338State),
  54         VMSTATE_UINT8_V(wday_offset, DS1338State, 2),
  55         VMSTATE_UINT8_ARRAY(nvram, DS1338State, NVRAM_SIZE),
  56         VMSTATE_INT32(ptr, DS1338State),
  57         VMSTATE_BOOL(addr_byte, DS1338State),
  58         VMSTATE_END_OF_LIST()
  59     }
  60 };
  61
  62 static void capture_current_time(DS1338State *s)
  63 {
  64     /* Capture the current time into the secondary registers
  65      * which will be actually read by the data transfer operation.
  66      */
  67     struct tm now;
  68     qemu_get_timedate(&now, s->offset);
  69     s->nvram[0] = to_bcd(now.tm_sec);
  70     s->nvram[1] = to_bcd(now.tm_min);
  71     if (s->nvram[2] & HOURS_12) {
  72         int tmp = now.tm_hour;
  73         if (tmp % 12 == 0) {
  74             tmp += 12;
  75         }
  76         if (tmp <= 12) {
  77             s->nvram[2] = HOURS_12 | to_bcd(tmp);
  78         } else {
  79             s->nvram[2] = HOURS_12 | HOURS_PM | to_bcd(tmp - 12);
  80         }
  81     } else {
  82         s->nvram[2] = to_bcd(now.tm_hour);
  83     }
  84     s->nvram[3] = (now.tm_wday + s->wday_offset) % 7 + 1;
  85     s->nvram[4] = to_bcd(now.tm_mday);
  86     s->nvram[5] = to_bcd(now.tm_mon + 1);
  87     s->nvram[6] = to_bcd(now.tm_year - 100);
  88 }
  89
  90 static void inc_regptr(DS1338State *s)
  91 {
  92     /* The register pointer wraps around after 0x3F; wraparound
  93      * causes the current time/date to be retransferred into
  94      * the secondary registers.
  95      */
  96     s->ptr = (s->ptr + 1) & (NVRAM_SIZE - 1);
  97     if (!s->ptr) {
  98         capture_current_time(s);
  99     }
 100 }
 101
 102 static int ds1338_event(I2CSlave *i2c, enum i2c_event event)
 103 {
 104     DS1338State *s = DS1338(i2c);
 105
 106     switch (event) {
 107     case I2C_START_RECV:
 108         /* In h/w, capture happens on any START condition, not just a
 109          * START_RECV, but there is no need to actually capture on
 110          * START_SEND, because the guest can't get at that data
 111          * without going through a START_RECV which would overwrite it.
 112          */
 113         capture_current_time(s);
 114         break;
 115     case I2C_START_SEND:
 116         s->addr_byte = true;
 117         break;
 118     default:
 119         break;
 120     }
 121
 122     return 0;
 123 }
 124
 125 static uint8_t ds1338_recv(I2CSlave *i2c)
 126 {
 127     DS1338State *s = DS1338(i2c);
 128     uint8_t res;
 129
 130     res  = s->nvram[s->ptr];
 131     inc_regptr(s);
 132     return res;
 133 }
 134
 135 static int ds1338_send(I2CSlave *i2c, uint8_t data)
 136 {
 137     DS1338State *s = DS1338(i2c);
 138
 139     if (s->addr_byte) {
 140         s->ptr = data & (NVRAM_SIZE - 1);
 141         s->addr_byte = false;
 142         return 0;
 143     }
 144     if (s->ptr < 7) {
 145         /* Time register. */
 146         struct tm now;
 147         qemu_get_timedate(&now, s->offset);
 148         switch(s->ptr) {
 149         case 0:
 150             /* TODO: Implement CH (stop) bit.  */
 151             now.tm_sec = from_bcd(data & 0x7f);
 152             break;
 153         case 1:
 154             now.tm_min = from_bcd(data & 0x7f);
 155             break;
 156         case 2:
 157             if (data & HOURS_12) {
 158                 int tmp = from_bcd(data & (HOURS_PM - 1));
 159                 if (data & HOURS_PM) {
 160                     tmp += 12;
 161                 }
 162                 if (tmp % 12 == 0) {
 163                     tmp -= 12;
 164                 }
 165                 now.tm_hour = tmp;
 166             } else {
 167                 now.tm_hour = from_bcd(data & (HOURS_12 - 1));
 168             }
 169             break;
 170         case 3:
 171             {
 172                 /* The day field is supposed to contain a value in
 173                    the range 1-7. Otherwise behavior is undefined.
 174                  */
 175                 int user_wday = (data & 7) - 1;
 176                 s->wday_offset = (user_wday - now.tm_wday + 7) % 7;
 177             }
 178             break;
 179         case 4:
 180             now.tm_mday = from_bcd(data & 0x3f);
 181             break;
 182         case 5:
 183             now.tm_mon = from_bcd(data & 0x1f) - 1;
 184             break;
 185         case 6:
 186             now.tm_year = from_bcd(data) + 100;
 187             break;
 188         }
 189         s->offset = qemu_timedate_diff(&now);
 190     } else if (s->ptr == 7) {
 191         /* Control register. */
 192
 193         /* Ensure bits 2, 3 and 6 will read back as zero. */
 194         data &= 0xB3;
 195
 196         /* Attempting to write the OSF flag to logic 1 leaves the
 197            value unchanged. */
 198         data = (data & ~CTRL_OSF) | (data & s->nvram[s->ptr] & CTRL_OSF);
 199
 200         s->nvram[s->ptr] = data;
 201     } else {
 202         s->nvram[s->ptr] = data;
 203     }
 204     inc_regptr(s);
 205     return 0;
 206 }
 207
 208 static void ds1338_reset(DeviceState *dev)
 209 {
 210     DS1338State *s = DS1338(dev);
 211
 212     /* The clock is running and synchronized with the host */
 213     s->offset = 0;
 214     s->wday_offset = 0;
 215     memset(s->nvram, 0, NVRAM_SIZE);
 216     s->ptr = 0;
 217     s->addr_byte = false;
 218 }
 219
 220 static void ds1338_class_init(ObjectClass *klass, void *data)
 221 {
 222     DeviceClass *dc = DEVICE_CLASS(klass);
 223     I2CSlaveClass *k = I2C_SLAVE_CLASS(klass);
 224
 225     k->event = ds1338_event;
 226     k->recv = ds1338_recv;
 227     k->send = ds1338_send;
 228     dc->reset = ds1338_reset;
 229     dc->vmsd = &vmstate_ds1338;
 230 }
 231
 232 static const TypeInfo ds1338_info = {
 233     .name          = TYPE_DS1338,
 234     .parent        = TYPE_I2C_SLAVE,
 235     .instance_size = sizeof(DS1338State),
 236     .class_init    = ds1338_class_init,
 237 };
 238
 239 static void ds1338_register_types(void)
 240 {
 241     type_register_static(&ds1338_info);
 242 }
 243
 244 type_init(ds1338_register_types)