hw/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://www.milkymist.org/socdoc/uart.pdf
  22  */
  23
  24 #include "hw.h"
  25 #include "sysbus.h"
  26 #include "trace.h"
  27 #include "qemu-char.h"
  28 #include "qemu-error.h"
  29
  30 enum {
  31     R_RXTX = 0,
  32     R_DIV,
  33     R_STAT,
  34     R_CTRL,
  35     R_DBG,
  36     R_MAX
  37 };
  38
  39 enum {
  40     STAT_THRE   = (1<<0),
  41     STAT_RX_EVT = (1<<1),
  42     STAT_TX_EVT = (1<<2),
  43 };
  44
  45 enum {
  46     CTRL_RX_IRQ_EN = (1<<0),
  47     CTRL_TX_IRQ_EN = (1<<1),
  48     CTRL_THRU_EN   = (1<<2),
  49 };
  50
  51 enum {
  52     DBG_BREAK_EN = (1<<0),
  53 };
  54
  55 struct MilkymistUartState {
  56     SysBusDevice busdev;
  57     MemoryRegion regs_region;
  58     CharDriverState *chr;
  59     qemu_irq irq;
  60
  61     uint32_t regs[R_MAX];
  62 };
  63 typedef struct MilkymistUartState MilkymistUartState;
  64
  65 static void uart_update_irq(MilkymistUartState *s)
  66 {
  67     int rx_event = s->regs[R_STAT] & STAT_RX_EVT;
  68     int tx_event = s->regs[R_STAT] & STAT_TX_EVT;
  69     int rx_irq_en = s->regs[R_CTRL] & CTRL_RX_IRQ_EN;
  70     int tx_irq_en = s->regs[R_CTRL] & CTRL_TX_IRQ_EN;
  71
  72     if ((rx_irq_en && rx_event) || (tx_irq_en && tx_event)) {
  73         trace_milkymist_uart_raise_irq();
  74         qemu_irq_raise(s->irq);
  75     } else {
  76         trace_milkymist_uart_lower_irq();
  77         qemu_irq_lower(s->irq);
  78     }
  79 }
  80
  81 static uint64_t uart_read(void *opaque, target_phys_addr_t addr,
  82                           unsigned size)
  83 {
  84     MilkymistUartState *s = opaque;
  85     uint32_t r = 0;
  86
  87     addr >>= 2;
  88     switch (addr) {
  89     case R_RXTX:
  90         r = s->regs[addr];
  91         break;
  92     case R_DIV:
  93     case R_STAT:
  94     case R_CTRL:
  95     case R_DBG:
  96         r = s->regs[addr];
  97         break;
  98
  99     default:
 100         error_report("milkymist_uart: read access to unknown register 0x"
 101                 TARGET_FMT_plx, addr << 2);
 102         break;
 103     }
 104
 105     trace_milkymist_uart_memory_read(addr << 2, r);
 106
 107     return r;
 108 }
 109
 110 static void uart_write(void *opaque, target_phys_addr_t addr, uint64_t value,
 111                        unsigned size)
 112 {
 113     MilkymistUartState *s = opaque;
 114     unsigned char ch = value;
 115
 116     trace_milkymist_uart_memory_write(addr, value);
 117
 118     addr >>= 2;
 119     switch (addr) {
 120     case R_RXTX:
 121         if (s->chr) {
 122             qemu_chr_fe_write(s->chr, &ch, 1);
 123         }
 124         s->regs[R_STAT] |= STAT_TX_EVT;
 125         break;
 126     case R_DIV:
 127     case R_CTRL:
 128     case R_DBG:
 129         s->regs[addr] = value;
 130         break;
 131
 132     case R_STAT:
 133         /* write one to clear bits */
 134         s->regs[addr] &= ~(value & (STAT_RX_EVT | STAT_TX_EVT));
 135         break;
 136
 137     default:
 138         error_report("milkymist_uart: write access to unknown register 0x"
 139                 TARGET_FMT_plx, addr << 2);
 140         break;
 141     }
 142
 143     uart_update_irq(s);
 144 }
 145
 146 static const MemoryRegionOps uart_mmio_ops = {
 147     .read = uart_read,
 148     .write = uart_write,
 149     .valid = {
 150         .min_access_size = 4,
 151         .max_access_size = 4,
 152     },
 153     .endianness = DEVICE_NATIVE_ENDIAN,
 154 };
 155
 156 static void uart_rx(void *opaque, const uint8_t *buf, int size)
 157 {
 158     MilkymistUartState *s = opaque;
 159
 160     assert(!(s->regs[R_STAT] & STAT_RX_EVT));
 161
 162     s->regs[R_STAT] |= STAT_RX_EVT;
 163     s->regs[R_RXTX] = *buf;
 164
 165     uart_update_irq(s);
 166 }
 167
 168 static int uart_can_rx(void *opaque)
 169 {
 170     MilkymistUartState *s = opaque;
 171
 172     return !(s->regs[R_STAT] & STAT_RX_EVT);
 173 }
 174
 175 static void uart_event(void *opaque, int event)
 176 {
 177 }
 178
 179 static void milkymist_uart_reset(DeviceState *d)
 180 {
 181     MilkymistUartState *s = container_of(d, MilkymistUartState, busdev.qdev);
 182     int i;
 183
 184     for (i = 0; i < R_MAX; i++) {
 185         s->regs[i] = 0;
 186     }
 187
 188     /* THRE is always set */
 189     s->regs[R_STAT] = STAT_THRE;
 190 }
 191
 192 static int milkymist_uart_init(SysBusDevice *dev)
 193 {
 194     MilkymistUartState *s = FROM_SYSBUS(typeof(*s), dev);
 195
 196     sysbus_init_irq(dev, &s->irq);
 197
 198     memory_region_init_io(&s->regs_region, &uart_mmio_ops, s,
 199             "milkymist-uart", R_MAX * 4);
 200     sysbus_init_mmio(dev, &s->regs_region);
 201
 202     s->chr = qdev_init_chardev(&dev->qdev);
 203     if (s->chr) {
 204         qemu_chr_add_handlers(s->chr, uart_can_rx, uart_rx, uart_event, s);
 205     }
 206
 207     return 0;
 208 }
 209
 210 static const VMStateDescription vmstate_milkymist_uart = {
 211     .name = "milkymist-uart",
 212     .version_id = 1,
 213     .minimum_version_id = 1,
 214     .minimum_version_id_old = 1,
 215     .fields      = (VMStateField[]) {
 216         VMSTATE_UINT32_ARRAY(regs, MilkymistUartState, R_MAX),
 217         VMSTATE_END_OF_LIST()
 218     }
 219 };
 220
 221 static SysBusDeviceInfo milkymist_uart_info = {
 222     .init = milkymist_uart_init,
 223     .qdev.name  = "milkymist-uart",
 224     .qdev.size  = sizeof(MilkymistUartState),
 225     .qdev.vmsd  = &vmstate_milkymist_uart,
 226     .qdev.reset = milkymist_uart_reset,
 227 };
 228
 229 static void milkymist_uart_register(void)
 230 {
 231     sysbus_register_withprop(&milkymist_uart_info);
 232 }
 233
 234 device_init(milkymist_uart_register)