hw/serial.c

   1 /*
   2  * QEMU 16450 UART emulation
   3  *
   4  * Copyright (c) 2003-2004 Fabrice Bellard
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24 #include "vl.h"
  25
  26 //#define DEBUG_SERIAL
  27
  28 #define UART_LCR_DLAB   0x80    /* Divisor latch access bit */
  29
  30 #define UART_IER_MSI    0x08    /* Enable Modem status interrupt */
  31 #define UART_IER_RLSI   0x04    /* Enable receiver line status interrupt */
  32 #define UART_IER_THRI   0x02    /* Enable Transmitter holding register int. */
  33 #define UART_IER_RDI    0x01    /* Enable receiver data interrupt */
  34
  35 #define UART_IIR_NO_INT 0x01    /* No interrupts pending */
  36 #define UART_IIR_ID     0x06    /* Mask for the interrupt ID */
  37
  38 #define UART_IIR_MSI    0x00    /* Modem status interrupt */
  39 #define UART_IIR_THRI   0x02    /* Transmitter holding register empty */
  40 #define UART_IIR_RDI    0x04    /* Receiver data interrupt */
  41 #define UART_IIR_RLSI   0x06    /* Receiver line status interrupt */
  42
  43 /*
  44  * These are the definitions for the Modem Control Register
  45  */
  46 #define UART_MCR_LOOP   0x10    /* Enable loopback test mode */
  47 #define UART_MCR_OUT2   0x08    /* Out2 complement */
  48 #define UART_MCR_OUT1   0x04    /* Out1 complement */
  49 #define UART_MCR_RTS    0x02    /* RTS complement */
  50 #define UART_MCR_DTR    0x01    /* DTR complement */
  51
  52 /*
  53  * These are the definitions for the Modem Status Register
  54  */
  55 #define UART_MSR_DCD    0x80    /* Data Carrier Detect */
  56 #define UART_MSR_RI     0x40    /* Ring Indicator */
  57 #define UART_MSR_DSR    0x20    /* Data Set Ready */
  58 #define UART_MSR_CTS    0x10    /* Clear to Send */
  59 #define UART_MSR_DDCD   0x08    /* Delta DCD */
  60 #define UART_MSR_TERI   0x04    /* Trailing edge ring indicator */
  61 #define UART_MSR_DDSR   0x02    /* Delta DSR */
  62 #define UART_MSR_DCTS   0x01    /* Delta CTS */
  63 #define UART_MSR_ANY_DELTA 0x0F /* Any of the delta bits! */
  64
  65 #define UART_LSR_TEMT   0x40    /* Transmitter empty */
  66 #define UART_LSR_THRE   0x20    /* Transmit-hold-register empty */
  67 #define UART_LSR_BI     0x10    /* Break interrupt indicator */
  68 #define UART_LSR_FE     0x08    /* Frame error indicator */
  69 #define UART_LSR_PE     0x04    /* Parity error indicator */
  70 #define UART_LSR_OE     0x02    /* Overrun error indicator */
  71 #define UART_LSR_DR     0x01    /* Receiver data ready */
  72
  73 struct SerialState {
  74     uint8_t divider;
  75     uint8_t rbr; /* receive register */
  76     uint8_t ier;
  77     uint8_t iir; /* read only */
  78     uint8_t lcr;
  79     uint8_t mcr;
  80     uint8_t lsr; /* read only */
  81     uint8_t msr;
  82     uint8_t scr;
  83     /* NOTE: this hidden state is necessary for tx irq generation as
  84        it can be reset while reading iir */
  85     int thr_ipending;
  86     int irq;
  87     int out_fd;
  88 };
  89
  90 static void serial_update_irq(SerialState *s)
  91 {
  92     if ((s->lsr & UART_LSR_DR) && (s->ier & UART_IER_RDI)) {
  93         s->iir = UART_IIR_RDI;
  94     } else if (s->thr_ipending && (s->ier & UART_IER_THRI)) {
  95         s->iir = UART_IIR_THRI;
  96     } else {
  97         s->iir = UART_IIR_NO_INT;
  98     }
  99     if (s->iir != UART_IIR_NO_INT) {
 100         pic_set_irq(s->irq, 1);
 101     } else {
 102         pic_set_irq(s->irq, 0);
 103     }
 104 }
 105
 106 static void serial_ioport_write(void *opaque, uint32_t addr, uint32_t val)
 107 {
 108     SerialState *s = opaque;
 109     unsigned char ch;
 110     int ret;
 111
 112     addr &= 7;
 113 #ifdef DEBUG_SERIAL
 114     printf("serial: write addr=0x%02x val=0x%02x\n", addr, val);
 115 #endif
 116     switch(addr) {
 117     default:
 118     case 0:
 119         if (s->lcr & UART_LCR_DLAB) {
 120             s->divider = (s->divider & 0xff00) | val;
 121         } else {
 122             s->thr_ipending = 0;
 123             s->lsr &= ~UART_LSR_THRE;
 124             serial_update_irq(s);
 125
 126             if (s->out_fd >= 0) {
 127                 ch = val;
 128                 do {
 129                     ret = write(s->out_fd, &ch, 1);
 130                 } while (ret != 1);
 131             }
 132             s->thr_ipending = 1;
 133             s->lsr |= UART_LSR_THRE;
 134             s->lsr |= UART_LSR_TEMT;
 135             serial_update_irq(s);
 136         }
 137         break;
 138     case 1:
 139         if (s->lcr & UART_LCR_DLAB) {
 140             s->divider = (s->divider & 0x00ff) | (val << 8);
 141         } else {
 142             s->ier = val;
 143             serial_update_irq(s);
 144         }
 145         break;
 146     case 2:
 147         break;
 148     case 3:
 149         s->lcr = val;
 150         break;
 151     case 4:
 152         s->mcr = val;
 153         break;
 154     case 5:
 155         break;
 156     case 6:
 157         s->msr = val;
 158         break;
 159     case 7:
 160         s->scr = val;
 161         break;
 162     }
 163 }
 164
 165 static uint32_t serial_ioport_read(void *opaque, uint32_t addr)
 166 {
 167     SerialState *s = opaque;
 168     uint32_t ret;
 169
 170     addr &= 7;
 171     switch(addr) {
 172     default:
 173     case 0:
 174         if (s->lcr & UART_LCR_DLAB) {
 175             ret = s->divider & 0xff;
 176         } else {
 177             ret = s->rbr;
 178             s->lsr &= ~(UART_LSR_DR | UART_LSR_BI);
 179             serial_update_irq(s);
 180         }
 181         break;
 182     case 1:
 183         if (s->lcr & UART_LCR_DLAB) {
 184             ret = (s->divider >> 8) & 0xff;
 185         } else {
 186             ret = s->ier;
 187         }
 188         break;
 189     case 2:
 190         ret = s->iir;
 191         /* reset THR pending bit */
 192         if ((ret & 0x7) == UART_IIR_THRI)
 193             s->thr_ipending = 0;
 194         serial_update_irq(s);
 195         break;
 196     case 3:
 197         ret = s->lcr;
 198         break;
 199     case 4:
 200         ret = s->mcr;
 201         break;
 202     case 5:
 203         ret = s->lsr;
 204         break;
 205     case 6:
 206         if (s->mcr & UART_MCR_LOOP) {
 207             /* in loopback, the modem output pins are connected to the
 208                inputs */
 209             ret = (s->mcr & 0x0c) << 4;
 210             ret |= (s->mcr & 0x02) << 3;
 211             ret |= (s->mcr & 0x01) << 5;
 212         } else {
 213             ret = s->msr;
 214         }
 215         break;
 216     case 7:
 217         ret = s->scr;
 218         break;
 219     }
 220 #ifdef DEBUG_SERIAL
 221     printf("serial: read addr=0x%02x val=0x%02x\n", addr, ret);
 222 #endif
 223     return ret;
 224 }
 225
 226 int serial_can_receive(SerialState *s)
 227 {
 228     return !(s->lsr & UART_LSR_DR);
 229 }
 230
 231 void serial_receive_byte(SerialState *s, int ch)
 232 {
 233     s->rbr = ch;
 234     s->lsr |= UART_LSR_DR;
 235     serial_update_irq(s);
 236 }
 237
 238 void serial_receive_break(SerialState *s)
 239 {
 240     s->rbr = 0;
 241     s->lsr |= UART_LSR_BI | UART_LSR_DR;
 242     serial_update_irq(s);
 243 }
 244
 245 static int serial_can_receive1(void *opaque)
 246 {
 247     SerialState *s = opaque;
 248     return serial_can_receive(s);
 249 }
 250
 251 static void serial_receive1(void *opaque, const uint8_t *buf, int size)
 252 {
 253     SerialState *s = opaque;
 254     serial_receive_byte(s, buf[0]);
 255 }
 256
 257 /* If fd is zero, it means that the serial device uses the console */
 258 SerialState *serial_init(int base, int irq, int fd)
 259 {
 260     SerialState *s;
 261
 262     s = qemu_mallocz(sizeof(SerialState));
 263     if (!s)
 264         return NULL;
 265     s->irq = irq;
 266     s->lsr = UART_LSR_TEMT | UART_LSR_THRE;
 267     s->iir = UART_IIR_NO_INT;
 268
 269     register_ioport_write(base, 8, 1, serial_ioport_write, s);
 270     register_ioport_read(base, 8, 1, serial_ioport_read, s);
 271
 272     if (fd < 0) {
 273         /* no associated device */
 274         s->out_fd = -1;
 275     } else if (fd != 0) {
 276         qemu_add_fd_read_handler(fd, serial_can_receive1, serial_receive1, s);
 277         s->out_fd = fd;
 278     } else {
 279         serial_console = s;
 280         s->out_fd = 1;
 281     }
 282     return s;
 283 }