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/irq.h"
  26 #include "hw/sysbus.h"
  27 #include "migration/vmstate.h"
  28 #include "trace.h"
  29 #include "chardev/char-fe.h"
  30 #include "qemu/error-report.h"
  31 #include "qemu/module.h"
  32
  33 enum {
  34     R_RXTX = 0,
  35     R_DIV,
  36     R_STAT,
  37     R_CTRL,
  38     R_DBG,
  39     R_MAX
  40 };
  41
  42 enum {
  43     STAT_THRE   = (1<<0),
  44     STAT_RX_EVT = (1<<1),
  45     STAT_TX_EVT = (1<<2),
  46 };
  47
  48 enum {
  49     CTRL_RX_IRQ_EN = (1<<0),
  50     CTRL_TX_IRQ_EN = (1<<1),
  51     CTRL_THRU_EN   = (1<<2),
  52 };
  53
  54 enum {
  55     DBG_BREAK_EN = (1<<0),
  56 };
  57
  58 #define TYPE_MILKYMIST_UART "milkymist-uart"
  59 #define MILKYMIST_UART(obj) \
  60     OBJECT_CHECK(MilkymistUartState, (obj), TYPE_MILKYMIST_UART)
  61
  62 struct MilkymistUartState {
  63     SysBusDevice parent_obj;
  64
  65     MemoryRegion regs_region;
  66     CharBackend chr;
  67     qemu_irq irq;
  68
  69     uint32_t regs[R_MAX];
  70 };
  71 typedef struct MilkymistUartState MilkymistUartState;
  72
  73 static void uart_update_irq(MilkymistUartState *s)
  74 {
  75     int rx_event = s->regs[R_STAT] & STAT_RX_EVT;
  76     int tx_event = s->regs[R_STAT] & STAT_TX_EVT;
  77     int rx_irq_en = s->regs[R_CTRL] & CTRL_RX_IRQ_EN;
  78     int tx_irq_en = s->regs[R_CTRL] & CTRL_TX_IRQ_EN;
  79
  80     if ((rx_irq_en && rx_event) || (tx_irq_en && tx_event)) {
  81         trace_milkymist_uart_raise_irq();
  82         qemu_irq_raise(s->irq);
  83     } else {
  84         trace_milkymist_uart_lower_irq();
  85         qemu_irq_lower(s->irq);
  86     }
  87 }
  88
  89 static uint64_t uart_read(void *opaque, hwaddr addr,
  90                           unsigned size)
  91 {
  92     MilkymistUartState *s = opaque;
  93     uint32_t r = 0;
  94
  95     addr >>= 2;
  96     switch (addr) {
  97     case R_RXTX:
  98         r = s->regs[addr];
  99         break;
 100     case R_DIV:
 101     case R_STAT:
 102     case R_CTRL:
 103     case R_DBG:
 104         r = s->regs[addr];
 105         break;
 106
 107     default:
 108         error_report("milkymist_uart: read access to unknown register 0x"
 109                 TARGET_FMT_plx, addr << 2);
 110         break;
 111     }
 112
 113     trace_milkymist_uart_memory_read(addr << 2, r);
 114
 115     return r;
 116 }
 117
 118 static void uart_write(void *opaque, hwaddr addr, uint64_t value,
 119                        unsigned size)
 120 {
 121     MilkymistUartState *s = opaque;
 122     unsigned char ch = value;
 123
 124     trace_milkymist_uart_memory_write(addr, value);
 125
 126     addr >>= 2;
 127     switch (addr) {
 128     case R_RXTX:
 129         qemu_chr_fe_write_all(&s->chr, &ch, 1);
 130         s->regs[R_STAT] |= STAT_TX_EVT;
 131         break;
 132     case R_DIV:
 133     case R_CTRL:
 134     case R_DBG:
 135         s->regs[addr] = value;
 136         break;
 137
 138     case R_STAT:
 139         /* write one to clear bits */
 140         s->regs[addr] &= ~(value & (STAT_RX_EVT | STAT_TX_EVT));
 141         qemu_chr_fe_accept_input(&s->chr);
 142         break;
 143
 144     default:
 145         error_report("milkymist_uart: write access to unknown register 0x"
 146                 TARGET_FMT_plx, addr << 2);
 147         break;
 148     }
 149
 150     uart_update_irq(s);
 151 }
 152
 153 static const MemoryRegionOps uart_mmio_ops = {
 154     .read = uart_read,
 155     .write = uart_write,
 156     .valid = {
 157         .min_access_size = 4,
 158         .max_access_size = 4,
 159     },
 160     .endianness = DEVICE_NATIVE_ENDIAN,
 161 };
 162
 163 static void uart_rx(void *opaque, const uint8_t *buf, int size)
 164 {
 165     MilkymistUartState *s = opaque;
 166
 167     assert(!(s->regs[R_STAT] & STAT_RX_EVT));
 168
 169     s->regs[R_STAT] |= STAT_RX_EVT;
 170     s->regs[R_RXTX] = *buf;
 171
 172     uart_update_irq(s);
 173 }
 174
 175 static int uart_can_rx(void *opaque)
 176 {
 177     MilkymistUartState *s = opaque;
 178
 179     return !(s->regs[R_STAT] & STAT_RX_EVT);
 180 }
 181
 182 static void uart_event(void *opaque, int event)
 183 {
 184 }
 185
 186 static void milkymist_uart_reset(DeviceState *d)
 187 {
 188     MilkymistUartState *s = MILKYMIST_UART(d);
 189     int i;
 190
 191     for (i = 0; i < R_MAX; i++) {
 192         s->regs[i] = 0;
 193     }
 194
 195     /* THRE is always set */
 196     s->regs[R_STAT] = STAT_THRE;
 197 }
 198
 199 static void milkymist_uart_realize(DeviceState *dev, Error **errp)
 200 {
 201     MilkymistUartState *s = MILKYMIST_UART(dev);
 202
 203     qemu_chr_fe_set_handlers(&s->chr, uart_can_rx, uart_rx,
 204                              uart_event, NULL, s, NULL, true);
 205 }
 206
 207 static void milkymist_uart_init(Object *obj)
 208 {
 209     SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
 210     MilkymistUartState *s = MILKYMIST_UART(obj);
 211
 212     sysbus_init_irq(sbd, &s->irq);
 213
 214     memory_region_init_io(&s->regs_region, OBJECT(s), &uart_mmio_ops, s,
 215                           "milkymist-uart", R_MAX * 4);
 216     sysbus_init_mmio(sbd, &s->regs_region);
 217 }
 218
 219 static const VMStateDescription vmstate_milkymist_uart = {
 220     .name = "milkymist-uart",
 221     .version_id = 1,
 222     .minimum_version_id = 1,
 223     .fields = (VMStateField[]) {
 224         VMSTATE_UINT32_ARRAY(regs, MilkymistUartState, R_MAX),
 225         VMSTATE_END_OF_LIST()
 226     }
 227 };
 228
 229 static Property milkymist_uart_properties[] = {
 230     DEFINE_PROP_CHR("chardev", MilkymistUartState, chr),
 231     DEFINE_PROP_END_OF_LIST(),
 232 };
 233
 234 static void milkymist_uart_class_init(ObjectClass *klass, void *data)
 235 {
 236     DeviceClass *dc = DEVICE_CLASS(klass);
 237
 238     dc->realize = milkymist_uart_realize;
 239     dc->reset = milkymist_uart_reset;
 240     dc->vmsd = &vmstate_milkymist_uart;
 241     dc->props = milkymist_uart_properties;
 242 }
 243
 244 static const TypeInfo milkymist_uart_info = {
 245     .name          = TYPE_MILKYMIST_UART,
 246     .parent        = TYPE_SYS_BUS_DEVICE,
 247     .instance_size = sizeof(MilkymistUartState),
 248     .instance_init = milkymist_uart_init,
 249     .class_init    = milkymist_uart_class_init,
 250 };
 251
 252 static void milkymist_uart_register_types(void)
 253 {
 254     type_register_static(&milkymist_uart_info);
 255 }
 256
 257 type_init(milkymist_uart_register_types)