hw/char/milkymist-uart.c

   1 /*
   2  *  QEMU model of the Milkymist UART block.
   3  *
   4  *  Copyright (c) 2010 Michael Walle <michael@walle.cc>
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  18  *
  19  *
  20  * Specification available at:
  21  *   http://milkymist.walle.cc/socdoc/uart.pdf
  22  */
  23
  24 #include "qemu/osdep.h"
  25 #include "hw/hw.h"
  26 #include "hw/sysbus.h"
  27 #include "trace.h"
  28 #include "chardev/char-fe.h"
  29 #include "qemu/error-report.h"
  30
  31 enum {
  32     R_RXTX = 0,
  33     R_DIV,
  34     R_STAT,
  35     R_CTRL,
  36     R_DBG,
  37     R_MAX
  38 };
  39
  40 enum {
  41     STAT_THRE   = (1<<0),
  42     STAT_RX_EVT = (1<<1),
  43     STAT_TX_EVT = (1<<2),
  44 };
  45
  46 enum {
  47     CTRL_RX_IRQ_EN = (1<<0),
  48     CTRL_TX_IRQ_EN = (1<<1),
  49     CTRL_THRU_EN   = (1<<2),
  50 };
  51
  52 enum {
  53     DBG_BREAK_EN = (1<<0),
  54 };
  55
  56 #define TYPE_MILKYMIST_UART "milkymist-uart"
  57 #define MILKYMIST_UART(obj) \
  58     OBJECT_CHECK(MilkymistUartState, (obj), TYPE_MILKYMIST_UART)
  59
  60 struct MilkymistUartState {
  61     SysBusDevice parent_obj;
  62
  63     MemoryRegion regs_region;
  64     CharBackend chr;
  65     qemu_irq irq;
  66
  67     uint32_t regs[R_MAX];
  68 };
  69 typedef struct MilkymistUartState MilkymistUartState;
  70
  71 static void uart_update_irq(MilkymistUartState *s)
  72 {
  73     int rx_event = s->regs[R_STAT] & STAT_RX_EVT;
  74     int tx_event = s->regs[R_STAT] & STAT_TX_EVT;
  75     int rx_irq_en = s->regs[R_CTRL] & CTRL_RX_IRQ_EN;
  76     int tx_irq_en = s->regs[R_CTRL] & CTRL_TX_IRQ_EN;
  77
  78     if ((rx_irq_en && rx_event) || (tx_irq_en && tx_event)) {
  79         trace_milkymist_uart_raise_irq();
  80         qemu_irq_raise(s->irq);
  81     } else {
  82         trace_milkymist_uart_lower_irq();
  83         qemu_irq_lower(s->irq);
  84     }
  85 }
  86
  87 static uint64_t uart_read(void *opaque, hwaddr addr,
  88                           unsigned size)
  89 {
  90     MilkymistUartState *s = opaque;
  91     uint32_t r = 0;
  92
  93     addr >>= 2;
  94     switch (addr) {
  95     case R_RXTX:
  96         r = s->regs[addr];
  97         break;
  98     case R_DIV:
  99     case R_STAT:
 100     case R_CTRL:
 101     case R_DBG:
 102         r = s->regs[addr];
 103         break;
 104
 105     default:
 106         error_report("milkymist_uart: read access to unknown register 0x"
 107                 TARGET_FMT_plx, addr << 2);
 108         break;
 109     }
 110
 111     trace_milkymist_uart_memory_read(addr << 2, r);
 112
 113     return r;
 114 }
 115
 116 static void uart_write(void *opaque, hwaddr addr, uint64_t value,
 117                        unsigned size)
 118 {
 119     MilkymistUartState *s = opaque;
 120     unsigned char ch = value;
 121
 122     trace_milkymist_uart_memory_write(addr, value);
 123
 124     addr >>= 2;
 125     switch (addr) {
 126     case R_RXTX:
 127         qemu_chr_fe_write_all(&s->chr, &ch, 1);
 128         s->regs[R_STAT] |= STAT_TX_EVT;
 129         break;
 130     case R_DIV:
 131     case R_CTRL:
 132     case R_DBG:
 133         s->regs[addr] = value;
 134         break;
 135
 136     case R_STAT:
 137         /* write one to clear bits */
 138         s->regs[addr] &= ~(value & (STAT_RX_EVT | STAT_TX_EVT));
 139         qemu_chr_fe_accept_input(&s->chr);
 140         break;
 141
 142     default:
 143         error_report("milkymist_uart: write access to unknown register 0x"
 144                 TARGET_FMT_plx, addr << 2);
 145         break;
 146     }
 147
 148     uart_update_irq(s);
 149 }
 150
 151 static const MemoryRegionOps uart_mmio_ops = {
 152     .read = uart_read,
 153     .write = uart_write,
 154     .valid = {
 155         .min_access_size = 4,
 156         .max_access_size = 4,
 157     },
 158     .endianness = DEVICE_NATIVE_ENDIAN,
 159 };
 160
 161 static void uart_rx(void *opaque, const uint8_t *buf, int size)
 162 {
 163     MilkymistUartState *s = opaque;
 164
 165     assert(!(s->regs[R_STAT] & STAT_RX_EVT));
 166
 167     s->regs[R_STAT] |= STAT_RX_EVT;
 168     s->regs[R_RXTX] = *buf;
 169
 170     uart_update_irq(s);
 171 }
 172
 173 static int uart_can_rx(void *opaque)
 174 {
 175     MilkymistUartState *s = opaque;
 176
 177     return !(s->regs[R_STAT] & STAT_RX_EVT);
 178 }
 179
 180 static void uart_event(void *opaque, int event)
 181 {
 182 }
 183
 184 static void milkymist_uart_reset(DeviceState *d)
 185 {
 186     MilkymistUartState *s = MILKYMIST_UART(d);
 187     int i;
 188
 189     for (i = 0; i < R_MAX; i++) {
 190         s->regs[i] = 0;
 191     }
 192
 193     /* THRE is always set */
 194     s->regs[R_STAT] = STAT_THRE;
 195 }
 196
 197 static void milkymist_uart_realize(DeviceState *dev, Error **errp)
 198 {
 199     MilkymistUartState *s = MILKYMIST_UART(dev);
 200
 201     qemu_chr_fe_set_handlers(&s->chr, uart_can_rx, uart_rx,
 202                              uart_event, NULL, s, NULL, true);
 203 }
 204
 205 static void milkymist_uart_init(Object *obj)
 206 {
 207     SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
 208     MilkymistUartState *s = MILKYMIST_UART(obj);
 209
 210     sysbus_init_irq(sbd, &s->irq);
 211
 212     memory_region_init_io(&s->regs_region, OBJECT(s), &uart_mmio_ops, s,
 213                           "milkymist-uart", R_MAX * 4);
 214     sysbus_init_mmio(sbd, &s->regs_region);
 215 }
 216
 217 static const VMStateDescription vmstate_milkymist_uart = {
 218     .name = "milkymist-uart",
 219     .version_id = 1,
 220     .minimum_version_id = 1,
 221     .fields = (VMStateField[]) {
 222         VMSTATE_UINT32_ARRAY(regs, MilkymistUartState, R_MAX),
 223         VMSTATE_END_OF_LIST()
 224     }
 225 };
 226
 227 static Property milkymist_uart_properties[] = {
 228     DEFINE_PROP_CHR("chardev", MilkymistUartState, chr),
 229     DEFINE_PROP_END_OF_LIST(),
 230 };
 231
 232 static void milkymist_uart_class_init(ObjectClass *klass, void *data)
 233 {
 234     DeviceClass *dc = DEVICE_CLASS(klass);
 235
 236     dc->realize = milkymist_uart_realize;
 237     dc->reset = milkymist_uart_reset;
 238     dc->vmsd = &vmstate_milkymist_uart;
 239     dc->props = milkymist_uart_properties;
 240 }
 241
 242 static const TypeInfo milkymist_uart_info = {
 243     .name          = TYPE_MILKYMIST_UART,
 244     .parent        = TYPE_SYS_BUS_DEVICE,
 245     .instance_size = sizeof(MilkymistUartState),
 246     .instance_init = milkymist_uart_init,
 247     .class_init    = milkymist_uart_class_init,
 248 };
 249
 250 static void milkymist_uart_register_types(void)
 251 {
 252     type_register_static(&milkymist_uart_info);
 253 }
 254
 255 type_init(milkymist_uart_register_types)