2
* QEMU 16550A UART emulation
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* Copyright (c) 2003-2004 Fabrice Bellard
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* Copyright (c) 2008 Citrix Systems, Inc.
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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#include "hw/char/serial.h"
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#include "sysemu/char.h"
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#include "qemu/timer.h"
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#include "exec/address-spaces.h"
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//#define DEBUG_SERIAL
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#define UART_LCR_DLAB 0x80 /* Divisor latch access bit */
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#define UART_IER_MSI 0x08 /* Enable Modem status interrupt */
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#define UART_IER_RLSI 0x04 /* Enable receiver line status interrupt */
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#define UART_IER_THRI 0x02 /* Enable Transmitter holding register int. */
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#define UART_IER_RDI 0x01 /* Enable receiver data interrupt */
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#define UART_IIR_NO_INT 0x01 /* No interrupts pending */
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#define UART_IIR_ID 0x06 /* Mask for the interrupt ID */
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#define UART_IIR_MSI 0x00 /* Modem status interrupt */
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#define UART_IIR_THRI 0x02 /* Transmitter holding register empty */
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#define UART_IIR_RDI 0x04 /* Receiver data interrupt */
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#define UART_IIR_RLSI 0x06 /* Receiver line status interrupt */
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#define UART_IIR_CTI 0x0C /* Character Timeout Indication */
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#define UART_IIR_FENF 0x80 /* Fifo enabled, but not functionning */
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#define UART_IIR_FE 0xC0 /* Fifo enabled */
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* These are the definitions for the Modem Control Register
55
#define UART_MCR_LOOP 0x10 /* Enable loopback test mode */
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#define UART_MCR_OUT2 0x08 /* Out2 complement */
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#define UART_MCR_OUT1 0x04 /* Out1 complement */
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#define UART_MCR_RTS 0x02 /* RTS complement */
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#define UART_MCR_DTR 0x01 /* DTR complement */
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* These are the definitions for the Modem Status Register
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#define UART_MSR_DCD 0x80 /* Data Carrier Detect */
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#define UART_MSR_RI 0x40 /* Ring Indicator */
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#define UART_MSR_DSR 0x20 /* Data Set Ready */
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#define UART_MSR_CTS 0x10 /* Clear to Send */
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#define UART_MSR_DDCD 0x08 /* Delta DCD */
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#define UART_MSR_TERI 0x04 /* Trailing edge ring indicator */
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#define UART_MSR_DDSR 0x02 /* Delta DSR */
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#define UART_MSR_DCTS 0x01 /* Delta CTS */
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#define UART_MSR_ANY_DELTA 0x0F /* Any of the delta bits! */
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#define UART_LSR_TEMT 0x40 /* Transmitter empty */
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#define UART_LSR_THRE 0x20 /* Transmit-hold-register empty */
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#define UART_LSR_BI 0x10 /* Break interrupt indicator */
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#define UART_LSR_FE 0x08 /* Frame error indicator */
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#define UART_LSR_PE 0x04 /* Parity error indicator */
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#define UART_LSR_OE 0x02 /* Overrun error indicator */
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#define UART_LSR_DR 0x01 /* Receiver data ready */
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#define UART_LSR_INT_ANY 0x1E /* Any of the lsr-interrupt-triggering status bits */
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/* Interrupt trigger levels. The byte-counts are for 16550A - in newer UARTs the byte-count for each ITL is higher. */
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#define UART_FCR_ITL_1 0x00 /* 1 byte ITL */
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#define UART_FCR_ITL_2 0x40 /* 4 bytes ITL */
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#define UART_FCR_ITL_3 0x80 /* 8 bytes ITL */
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#define UART_FCR_ITL_4 0xC0 /* 14 bytes ITL */
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#define UART_FCR_DMS 0x08 /* DMA Mode Select */
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#define UART_FCR_XFR 0x04 /* XMIT Fifo Reset */
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#define UART_FCR_RFR 0x02 /* RCVR Fifo Reset */
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#define UART_FCR_FE 0x01 /* FIFO Enable */
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#define MAX_XMIT_RETRY 4
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#define DPRINTF(fmt, ...) \
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do { fprintf(stderr, "serial: " fmt , ## __VA_ARGS__); } while (0)
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#define DPRINTF(fmt, ...) \
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static void serial_receive1(void *opaque, const uint8_t *buf, int size);
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static inline void recv_fifo_put(SerialState *s, uint8_t chr)
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/* Receive overruns do not overwrite FIFO contents. */
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if (!fifo8_is_full(&s->recv_fifo)) {
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fifo8_push(&s->recv_fifo, chr);
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s->lsr |= UART_LSR_OE;
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static void serial_update_irq(SerialState *s)
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uint8_t tmp_iir = UART_IIR_NO_INT;
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if ((s->ier & UART_IER_RLSI) && (s->lsr & UART_LSR_INT_ANY)) {
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tmp_iir = UART_IIR_RLSI;
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} else if ((s->ier & UART_IER_RDI) && s->timeout_ipending) {
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/* Note that(s->ier & UART_IER_RDI) can mask this interrupt,
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* this is not in the specification but is observed on existing
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tmp_iir = UART_IIR_CTI;
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} else if ((s->ier & UART_IER_RDI) && (s->lsr & UART_LSR_DR) &&
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(!(s->fcr & UART_FCR_FE) ||
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s->recv_fifo.num >= s->recv_fifo_itl)) {
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tmp_iir = UART_IIR_RDI;
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} else if ((s->ier & UART_IER_THRI) && s->thr_ipending) {
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tmp_iir = UART_IIR_THRI;
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} else if ((s->ier & UART_IER_MSI) && (s->msr & UART_MSR_ANY_DELTA)) {
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tmp_iir = UART_IIR_MSI;
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s->iir = tmp_iir | (s->iir & 0xF0);
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if (tmp_iir != UART_IIR_NO_INT) {
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qemu_irq_raise(s->irq);
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qemu_irq_lower(s->irq);
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static void serial_update_parameters(SerialState *s)
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int speed, parity, data_bits, stop_bits, frame_size;
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QEMUSerialSetParams ssp;
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data_bits = (s->lcr & 0x03) + 5;
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frame_size += data_bits + stop_bits;
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speed = s->baudbase / s->divider;
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ssp.data_bits = data_bits;
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ssp.stop_bits = stop_bits;
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s->char_transmit_time = (get_ticks_per_sec() / speed) * frame_size;
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qemu_chr_fe_ioctl(s->chr, CHR_IOCTL_SERIAL_SET_PARAMS, &ssp);
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DPRINTF("speed=%d parity=%c data=%d stop=%d\n",
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speed, parity, data_bits, stop_bits);
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static void serial_update_msl(SerialState *s)
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qemu_del_timer(s->modem_status_poll);
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if (qemu_chr_fe_ioctl(s->chr,CHR_IOCTL_SERIAL_GET_TIOCM, &flags) == -ENOTSUP) {
200
s->msr = (flags & CHR_TIOCM_CTS) ? s->msr | UART_MSR_CTS : s->msr & ~UART_MSR_CTS;
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s->msr = (flags & CHR_TIOCM_DSR) ? s->msr | UART_MSR_DSR : s->msr & ~UART_MSR_DSR;
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s->msr = (flags & CHR_TIOCM_CAR) ? s->msr | UART_MSR_DCD : s->msr & ~UART_MSR_DCD;
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s->msr = (flags & CHR_TIOCM_RI) ? s->msr | UART_MSR_RI : s->msr & ~UART_MSR_RI;
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if (s->msr != omsr) {
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s->msr = s->msr | ((s->msr >> 4) ^ (omsr >> 4));
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/* UART_MSR_TERI only if change was from 1 -> 0 */
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if ((s->msr & UART_MSR_TERI) && !(omsr & UART_MSR_RI))
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s->msr &= ~UART_MSR_TERI;
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serial_update_irq(s);
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/* The real 16550A apparently has a 250ns response latency to line status changes.
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We'll be lazy and poll only every 10ms, and only poll it at all if MSI interrupts are turned on */
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qemu_mod_timer(s->modem_status_poll, qemu_get_clock_ns(vm_clock) + get_ticks_per_sec() / 100);
221
static gboolean serial_xmit(GIOChannel *chan, GIOCondition cond, void *opaque)
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SerialState *s = opaque;
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if (s->tsr_retry <= 0) {
226
if (s->fcr & UART_FCR_FE) {
227
s->tsr = fifo8_is_full(&s->xmit_fifo) ?
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0 : fifo8_pop(&s->xmit_fifo);
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if (!s->xmit_fifo.num) {
230
s->lsr |= UART_LSR_THRE;
232
} else if ((s->lsr & UART_LSR_THRE)) {
236
s->lsr |= UART_LSR_THRE;
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s->lsr &= ~UART_LSR_TEMT;
241
if (s->mcr & UART_MCR_LOOP) {
242
/* in loopback mode, say that we just received a char */
243
serial_receive1(s, &s->tsr, 1);
244
} else if (qemu_chr_fe_write(s->chr, &s->tsr, 1) != 1) {
245
if (s->tsr_retry >= 0 && s->tsr_retry < MAX_XMIT_RETRY &&
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qemu_chr_fe_add_watch(s->chr, G_IO_OUT, serial_xmit, s) > 0) {
255
s->last_xmit_ts = qemu_get_clock_ns(vm_clock);
257
if (s->lsr & UART_LSR_THRE) {
258
s->lsr |= UART_LSR_TEMT;
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serial_update_irq(s);
267
static void serial_ioport_write(void *opaque, hwaddr addr, uint64_t val,
270
SerialState *s = opaque;
273
DPRINTF("write addr=0x%" HWADDR_PRIx " val=0x%" PRIx64 "\n", addr, val);
277
if (s->lcr & UART_LCR_DLAB) {
278
s->divider = (s->divider & 0xff00) | val;
279
serial_update_parameters(s);
281
s->thr = (uint8_t) val;
282
if(s->fcr & UART_FCR_FE) {
283
/* xmit overruns overwrite data, so make space if needed */
284
if (fifo8_is_full(&s->xmit_fifo)) {
285
fifo8_pop(&s->xmit_fifo);
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fifo8_push(&s->xmit_fifo, s->thr);
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s->lsr &= ~UART_LSR_TEMT;
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s->lsr &= ~UART_LSR_THRE;
292
serial_update_irq(s);
293
serial_xmit(NULL, G_IO_OUT, s);
297
if (s->lcr & UART_LCR_DLAB) {
298
s->divider = (s->divider & 0x00ff) | (val << 8);
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serial_update_parameters(s);
302
/* If the backend device is a real serial port, turn polling of the modem
303
status lines on physical port on or off depending on UART_IER_MSI state */
304
if (s->poll_msl >= 0) {
305
if (s->ier & UART_IER_MSI) {
307
serial_update_msl(s);
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qemu_del_timer(s->modem_status_poll);
313
if (s->lsr & UART_LSR_THRE) {
315
serial_update_irq(s);
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/* Did the enable/disable flag change? If so, make sure FIFOs get flushed */
326
if ((val ^ s->fcr) & UART_FCR_FE)
327
val |= UART_FCR_XFR | UART_FCR_RFR;
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if (val & UART_FCR_RFR) {
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qemu_del_timer(s->fifo_timeout_timer);
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s->timeout_ipending=0;
334
fifo8_reset(&s->recv_fifo);
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if ((s->lsr & UART_LSR_DR)) {
336
s->lsr &= ~(UART_LSR_DR | UART_LSR_BI | UART_LSR_OE);
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if (!(s->mcr & UART_MCR_LOOP)) {
338
qemu_chr_accept_input(s->chr);
343
if (val & UART_FCR_XFR) {
344
fifo8_reset(&s->xmit_fifo);
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s->lsr |= UART_LSR_THRE;
348
if (val & UART_FCR_FE) {
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s->iir |= UART_IIR_FE;
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/* Set recv_fifo trigger Level */
351
switch (val & 0xC0) {
353
s->recv_fifo_itl = 1;
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s->recv_fifo_itl = 4;
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s->recv_fifo_itl = 8;
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s->recv_fifo_itl = 14;
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s->iir &= ~UART_IIR_FE;
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/* Set fcr - or at least the bits in it that are supposed to "stick" */
370
serial_update_irq(s);
376
serial_update_parameters(s);
377
break_enable = (val >> 6) & 1;
378
if (break_enable != s->last_break_enable) {
379
s->last_break_enable = break_enable;
380
qemu_chr_fe_ioctl(s->chr, CHR_IOCTL_SERIAL_SET_BREAK,
388
int old_mcr = s->mcr;
390
if (val & UART_MCR_LOOP)
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if (s->poll_msl >= 0 && old_mcr != s->mcr) {
395
qemu_chr_fe_ioctl(s->chr,CHR_IOCTL_SERIAL_GET_TIOCM, &flags);
397
flags &= ~(CHR_TIOCM_RTS | CHR_TIOCM_DTR);
399
if (val & UART_MCR_RTS)
400
flags |= CHR_TIOCM_RTS;
401
if (val & UART_MCR_DTR)
402
flags |= CHR_TIOCM_DTR;
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qemu_chr_fe_ioctl(s->chr,CHR_IOCTL_SERIAL_SET_TIOCM, &flags);
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/* Update the modem status after a one-character-send wait-time, since there may be a response
406
from the device/computer at the other end of the serial line */
407
qemu_mod_timer(s->modem_status_poll, qemu_get_clock_ns(vm_clock) + s->char_transmit_time);
421
static uint64_t serial_ioport_read(void *opaque, hwaddr addr, unsigned size)
423
SerialState *s = opaque;
430
if (s->lcr & UART_LCR_DLAB) {
431
ret = s->divider & 0xff;
433
if(s->fcr & UART_FCR_FE) {
434
ret = fifo8_is_empty(&s->recv_fifo) ?
435
0 : fifo8_pop(&s->recv_fifo);
436
if (s->recv_fifo.num == 0) {
437
s->lsr &= ~(UART_LSR_DR | UART_LSR_BI);
439
qemu_mod_timer(s->fifo_timeout_timer, qemu_get_clock_ns (vm_clock) + s->char_transmit_time * 4);
441
s->timeout_ipending = 0;
444
s->lsr &= ~(UART_LSR_DR | UART_LSR_BI);
446
serial_update_irq(s);
447
if (!(s->mcr & UART_MCR_LOOP)) {
448
/* in loopback mode, don't receive any data */
449
qemu_chr_accept_input(s->chr);
454
if (s->lcr & UART_LCR_DLAB) {
455
ret = (s->divider >> 8) & 0xff;
462
if ((ret & UART_IIR_ID) == UART_IIR_THRI) {
464
serial_update_irq(s);
475
/* Clear break and overrun interrupts */
476
if (s->lsr & (UART_LSR_BI|UART_LSR_OE)) {
477
s->lsr &= ~(UART_LSR_BI|UART_LSR_OE);
478
serial_update_irq(s);
482
if (s->mcr & UART_MCR_LOOP) {
483
/* in loopback, the modem output pins are connected to the
485
ret = (s->mcr & 0x0c) << 4;
486
ret |= (s->mcr & 0x02) << 3;
487
ret |= (s->mcr & 0x01) << 5;
489
if (s->poll_msl >= 0)
490
serial_update_msl(s);
492
/* Clear delta bits & msr int after read, if they were set */
493
if (s->msr & UART_MSR_ANY_DELTA) {
495
serial_update_irq(s);
503
DPRINTF("read addr=0x%" HWADDR_PRIx " val=0x%02x\n", addr, ret);
507
static int serial_can_receive(SerialState *s)
509
if(s->fcr & UART_FCR_FE) {
510
if (s->recv_fifo.num < UART_FIFO_LENGTH) {
512
* Advertise (fifo.itl - fifo.count) bytes when count < ITL, and 1
513
* if above. If UART_FIFO_LENGTH - fifo.count is advertised the
514
* effect will be to almost always fill the fifo completely before
515
* the guest has a chance to respond, effectively overriding the ITL
516
* that the guest has set.
518
return (s->recv_fifo.num <= s->recv_fifo_itl) ?
519
s->recv_fifo_itl - s->recv_fifo.num : 1;
524
return !(s->lsr & UART_LSR_DR);
528
static void serial_receive_break(SerialState *s)
531
/* When the LSR_DR is set a null byte is pushed into the fifo */
532
recv_fifo_put(s, '\0');
533
s->lsr |= UART_LSR_BI | UART_LSR_DR;
534
serial_update_irq(s);
537
/* There's data in recv_fifo and s->rbr has not been read for 4 char transmit times */
538
static void fifo_timeout_int (void *opaque) {
539
SerialState *s = opaque;
540
if (s->recv_fifo.num) {
541
s->timeout_ipending = 1;
542
serial_update_irq(s);
546
static int serial_can_receive1(void *opaque)
548
SerialState *s = opaque;
549
return serial_can_receive(s);
552
static void serial_receive1(void *opaque, const uint8_t *buf, int size)
554
SerialState *s = opaque;
557
qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
559
if(s->fcr & UART_FCR_FE) {
561
for (i = 0; i < size; i++) {
562
recv_fifo_put(s, buf[i]);
564
s->lsr |= UART_LSR_DR;
565
/* call the timeout receive callback in 4 char transmit time */
566
qemu_mod_timer(s->fifo_timeout_timer, qemu_get_clock_ns (vm_clock) + s->char_transmit_time * 4);
568
if (s->lsr & UART_LSR_DR)
569
s->lsr |= UART_LSR_OE;
571
s->lsr |= UART_LSR_DR;
573
serial_update_irq(s);
576
static void serial_event(void *opaque, int event)
578
SerialState *s = opaque;
579
DPRINTF("event %x\n", event);
580
if (event == CHR_EVENT_BREAK)
581
serial_receive_break(s);
584
static void serial_pre_save(void *opaque)
586
SerialState *s = opaque;
587
s->fcr_vmstate = s->fcr;
590
static int serial_post_load(void *opaque, int version_id)
592
SerialState *s = opaque;
594
if (version_id < 3) {
597
/* Initialize fcr via setter to perform essential side-effects */
598
serial_ioport_write(s, 0x02, s->fcr_vmstate, 1);
599
serial_update_parameters(s);
603
const VMStateDescription vmstate_serial = {
606
.minimum_version_id = 2,
607
.pre_save = serial_pre_save,
608
.post_load = serial_post_load,
609
.fields = (VMStateField []) {
610
VMSTATE_UINT16_V(divider, SerialState, 2),
611
VMSTATE_UINT8(rbr, SerialState),
612
VMSTATE_UINT8(ier, SerialState),
613
VMSTATE_UINT8(iir, SerialState),
614
VMSTATE_UINT8(lcr, SerialState),
615
VMSTATE_UINT8(mcr, SerialState),
616
VMSTATE_UINT8(lsr, SerialState),
617
VMSTATE_UINT8(msr, SerialState),
618
VMSTATE_UINT8(scr, SerialState),
619
VMSTATE_UINT8_V(fcr_vmstate, SerialState, 3),
620
VMSTATE_END_OF_LIST()
624
static void serial_reset(void *opaque)
626
SerialState *s = opaque;
630
s->iir = UART_IIR_NO_INT;
632
s->lsr = UART_LSR_TEMT | UART_LSR_THRE;
633
s->msr = UART_MSR_DCD | UART_MSR_DSR | UART_MSR_CTS;
634
/* Default to 9600 baud, 1 start bit, 8 data bits, 1 stop bit, no parity. */
636
s->mcr = UART_MCR_OUT2;
639
s->char_transmit_time = (get_ticks_per_sec() / 9600) * 10;
642
fifo8_reset(&s->recv_fifo);
643
fifo8_reset(&s->xmit_fifo);
645
s->last_xmit_ts = qemu_get_clock_ns(vm_clock);
648
s->last_break_enable = 0;
649
qemu_irq_lower(s->irq);
652
void serial_realize_core(SerialState *s, Error **errp)
655
error_setg(errp, "Can't create serial device, empty char device");
659
s->modem_status_poll = qemu_new_timer_ns(vm_clock, (QEMUTimerCB *) serial_update_msl, s);
661
s->fifo_timeout_timer = qemu_new_timer_ns(vm_clock, (QEMUTimerCB *) fifo_timeout_int, s);
662
qemu_register_reset(serial_reset, s);
664
qemu_chr_add_handlers(s->chr, serial_can_receive1, serial_receive1,
666
fifo8_create(&s->recv_fifo, UART_FIFO_LENGTH);
667
fifo8_create(&s->xmit_fifo, UART_FIFO_LENGTH);
670
void serial_exit_core(SerialState *s)
672
qemu_chr_add_handlers(s->chr, NULL, NULL, NULL, NULL);
673
qemu_unregister_reset(serial_reset, s);
676
/* Change the main reference oscillator frequency. */
677
void serial_set_frequency(SerialState *s, uint32_t frequency)
679
s->baudbase = frequency;
680
serial_update_parameters(s);
683
const MemoryRegionOps serial_io_ops = {
684
.read = serial_ioport_read,
685
.write = serial_ioport_write,
687
.min_access_size = 1,
688
.max_access_size = 1,
690
.endianness = DEVICE_LITTLE_ENDIAN,
693
SerialState *serial_init(int base, qemu_irq irq, int baudbase,
694
CharDriverState *chr, MemoryRegion *system_io)
699
s = g_malloc0(sizeof(SerialState));
702
s->baudbase = baudbase;
704
serial_realize_core(s, &err);
706
fprintf(stderr, "%s\n", error_get_pretty(err));
711
vmstate_register(NULL, base, &vmstate_serial, s);
713
memory_region_init_io(&s->io, NULL, &serial_io_ops, s, "serial", 8);
714
memory_region_add_subregion(system_io, base, &s->io);
719
/* Memory mapped interface */
720
static uint64_t serial_mm_read(void *opaque, hwaddr addr,
723
SerialState *s = opaque;
724
return serial_ioport_read(s, addr >> s->it_shift, 1);
727
static void serial_mm_write(void *opaque, hwaddr addr,
728
uint64_t value, unsigned size)
730
SerialState *s = opaque;
731
value &= ~0u >> (32 - (size * 8));
732
serial_ioport_write(s, addr >> s->it_shift, value, 1);
735
static const MemoryRegionOps serial_mm_ops[3] = {
736
[DEVICE_NATIVE_ENDIAN] = {
737
.read = serial_mm_read,
738
.write = serial_mm_write,
739
.endianness = DEVICE_NATIVE_ENDIAN,
741
[DEVICE_LITTLE_ENDIAN] = {
742
.read = serial_mm_read,
743
.write = serial_mm_write,
744
.endianness = DEVICE_LITTLE_ENDIAN,
746
[DEVICE_BIG_ENDIAN] = {
747
.read = serial_mm_read,
748
.write = serial_mm_write,
749
.endianness = DEVICE_BIG_ENDIAN,
753
SerialState *serial_mm_init(MemoryRegion *address_space,
754
hwaddr base, int it_shift,
755
qemu_irq irq, int baudbase,
756
CharDriverState *chr, enum device_endian end)
761
s = g_malloc0(sizeof(SerialState));
763
s->it_shift = it_shift;
765
s->baudbase = baudbase;
768
serial_realize_core(s, &err);
770
fprintf(stderr, "%s\n", error_get_pretty(err));
774
vmstate_register(NULL, base, &vmstate_serial, s);
777
memory_region_init_io(&s->io, NULL, &serial_mm_ops[end], s,
778
"serial", 8 << it_shift);
779
memory_region_add_subregion(address_space, base, &s->io);
782
serial_update_msl(s);
786
void serial_change_char_driver(SerialState *s, CharDriverState *chr)
788
/* TODO this is somewhat guesswork, and pretty ugly anyhow */
789
qemu_chr_add_handlers(s->chr, NULL, NULL, NULL, NULL);
791
qemu_chr_add_handlers(s->chr, serial_can_receive1, serial_receive1,
793
serial_update_msl(s);
796
const MemoryRegionOps *serial_get_memops(enum device_endian end)
798
return &serial_mm_ops[end];
801
qemu_irq *serial_get_irq(SerialState *s)