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     .minimum_version_id_old = 1,
  44     .fields = (VMStateField[]) {
  45         VMSTATE_I2C_SLAVE(parent_obj, DS1338State),
  46         VMSTATE_INT64(offset, DS1338State),
  47         VMSTATE_UINT8_V(wday_offset, DS1338State, 2),
  48         VMSTATE_UINT8_ARRAY(nvram, DS1338State, NVRAM_SIZE),
  49         VMSTATE_INT32(ptr, DS1338State),
  50         VMSTATE_BOOL(addr_byte, DS1338State),
  51         VMSTATE_END_OF_LIST()
  52     }
  53 };
  54
  55 static void capture_current_time(DS1338State *s)
  56 {
  57     /* Capture the current time into the secondary registers
  58      * which will be actually read by the data transfer operation.
  59      */
  60     struct tm now;
  61     qemu_get_timedate(&now, s->offset);
  62     s->nvram[0] = to_bcd(now.tm_sec);
  63     s->nvram[1] = to_bcd(now.tm_min);
  64     if (s->nvram[2] & HOURS_12) {
  65         int tmp = now.tm_hour;
  66         if (tmp % 12 == 0) {
  67             tmp += 12;
  68         }
  69         if (tmp <= 12) {
  70             s->nvram[2] = HOURS_12 | to_bcd(tmp);
  71         } else {
  72             s->nvram[2] = HOURS_12 | HOURS_PM | to_bcd(tmp - 12);
  73         }
  74     } else {
  75         s->nvram[2] = to_bcd(now.tm_hour);
  76     }
  77     s->nvram[3] = (now.tm_wday + s->wday_offset) % 7 + 1;
  78     s->nvram[4] = to_bcd(now.tm_mday);
  79     s->nvram[5] = to_bcd(now.tm_mon + 1);
  80     s->nvram[6] = to_bcd(now.tm_year - 100);
  81 }
  82
  83 static void inc_regptr(DS1338State *s)
  84 {
  85     /* The register pointer wraps around after 0x3F; wraparound
  86      * causes the current time/date to be retransferred into
  87      * the secondary registers.
  88      */
  89     s->ptr = (s->ptr + 1) & (NVRAM_SIZE - 1);
  90     if (!s->ptr) {
  91         capture_current_time(s);
  92     }
  93 }
  94
  95 static void ds1338_event(I2CSlave *i2c, enum i2c_event event)
  96 {
  97     DS1338State *s = DS1338(i2c);
  98
  99     switch (event) {
 100     case I2C_START_RECV:
 101         /* In h/w, capture happens on any START condition, not just a
 102          * START_RECV, but there is no need to actually capture on
 103          * START_SEND, because the guest can't get at that data
 104          * without going through a START_RECV which would overwrite it.
 105          */
 106         capture_current_time(s);
 107         break;
 108     case I2C_START_SEND:
 109         s->addr_byte = true;
 110         break;
 111     default:
 112         break;
 113     }
 114 }
 115
 116 static int ds1338_recv(I2CSlave *i2c)
 117 {
 118     DS1338State *s = DS1338(i2c);
 119     uint8_t res;
 120
 121     res  = s->nvram[s->ptr];
 122     inc_regptr(s);
 123     return res;
 124 }
 125
 126 static int ds1338_send(I2CSlave *i2c, uint8_t data)
 127 {
 128     DS1338State *s = DS1338(i2c);
 129
 130     if (s->addr_byte) {
 131         s->ptr = data & (NVRAM_SIZE - 1);
 132         s->addr_byte = false;
 133         return 0;
 134     }
 135     if (s->ptr < 7) {
 136         /* Time register. */
 137         struct tm now;
 138         qemu_get_timedate(&now, s->offset);
 139         switch(s->ptr) {
 140         case 0:
 141             /* TODO: Implement CH (stop) bit.  */
 142             now.tm_sec = from_bcd(data & 0x7f);
 143             break;
 144         case 1:
 145             now.tm_min = from_bcd(data & 0x7f);
 146             break;
 147         case 2:
 148             if (data & HOURS_12) {
 149                 int tmp = from_bcd(data & (HOURS_PM - 1));
 150                 if (data & HOURS_PM) {
 151                     tmp += 12;
 152                 }
 153                 if (tmp % 12 == 0) {
 154                     tmp -= 12;
 155                 }
 156                 now.tm_hour = tmp;
 157             } else {
 158                 now.tm_hour = from_bcd(data & (HOURS_12 - 1));
 159             }
 160             break;
 161         case 3:
 162             {
 163                 /* The day field is supposed to contain a value in
 164                    the range 1-7. Otherwise behavior is undefined.
 165                  */
 166                 int user_wday = (data & 7) - 1;
 167                 s->wday_offset = (user_wday - now.tm_wday + 7) % 7;
 168             }
 169             break;
 170         case 4:
 171             now.tm_mday = from_bcd(data & 0x3f);
 172             break;
 173         case 5:
 174             now.tm_mon = from_bcd(data & 0x1f) - 1;
 175             break;
 176         case 6:
 177             now.tm_year = from_bcd(data) + 100;
 178             break;
 179         }
 180         s->offset = qemu_timedate_diff(&now);
 181     } else if (s->ptr == 7) {
 182         /* Control register. */
 183
 184         /* Ensure bits 2, 3 and 6 will read back as zero. */
 185         data &= 0xB3;
 186
 187         /* Attempting to write the OSF flag to logic 1 leaves the
 188            value unchanged. */
 189         data = (data & ~CTRL_OSF) | (data & s->nvram[s->ptr] & CTRL_OSF);
 190
 191         s->nvram[s->ptr] = data;
 192     } else {
 193         s->nvram[s->ptr] = data;
 194     }
 195     inc_regptr(s);
 196     return 0;
 197 }
 198
 199 static int ds1338_init(I2CSlave *i2c)
 200 {
 201     return 0;
 202 }
 203
 204 static void ds1338_reset(DeviceState *dev)
 205 {
 206     DS1338State *s = DS1338(dev);
 207
 208     /* The clock is running and synchronized with the host */
 209     s->offset = 0;
 210     s->wday_offset = 0;
 211     memset(s->nvram, 0, NVRAM_SIZE);
 212     s->ptr = 0;
 213     s->addr_byte = false;
 214 }
 215
 216 static void ds1338_class_init(ObjectClass *klass, void *data)
 217 {
 218     DeviceClass *dc = DEVICE_CLASS(klass);
 219     I2CSlaveClass *k = I2C_SLAVE_CLASS(klass);
 220
 221     k->init = ds1338_init;
 222     k->event = ds1338_event;
 223     k->recv = ds1338_recv;
 224     k->send = ds1338_send;
 225     dc->reset = ds1338_reset;
 226     dc->vmsd = &vmstate_ds1338;
 227 }
 228
 229 static const TypeInfo ds1338_info = {
 230     .name          = TYPE_DS1338,
 231     .parent        = TYPE_I2C_SLAVE,
 232     .instance_size = sizeof(DS1338State),
 233     .class_init    = ds1338_class_init,
 234 };
 235
 236 static void ds1338_register_types(void)
 237 {
 238     type_register_static(&ds1338_info);
 239 }
 240
 241 type_init(ds1338_register_types)