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