406 lines
12 KiB
C
406 lines
12 KiB
C
/*
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* ARM CMSDK APB UART emulation
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*
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* Copyright (c) 2017 Linaro Limited
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* Written by Peter Maydell
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 or
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* (at your option) any later version.
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*/
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/* This is a model of the "APB UART" which is part of the Cortex-M
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* System Design Kit (CMSDK) and documented in the Cortex-M System
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* Design Kit Technical Reference Manual (ARM DDI0479C):
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* https://developer.arm.com/products/system-design/system-design-kits/cortex-m-system-design-kit
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*/
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#include "qemu/osdep.h"
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#include "qemu/log.h"
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#include "qapi/error.h"
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#include "trace.h"
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#include "hw/sysbus.h"
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#include "hw/registerfields.h"
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#include "chardev/char-fe.h"
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#include "chardev/char-serial.h"
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#include "hw/char/cmsdk-apb-uart.h"
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REG32(DATA, 0)
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REG32(STATE, 4)
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FIELD(STATE, TXFULL, 0, 1)
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FIELD(STATE, RXFULL, 1, 1)
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FIELD(STATE, TXOVERRUN, 2, 1)
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FIELD(STATE, RXOVERRUN, 3, 1)
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REG32(CTRL, 8)
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FIELD(CTRL, TX_EN, 0, 1)
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FIELD(CTRL, RX_EN, 1, 1)
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FIELD(CTRL, TX_INTEN, 2, 1)
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FIELD(CTRL, RX_INTEN, 3, 1)
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FIELD(CTRL, TXO_INTEN, 4, 1)
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FIELD(CTRL, RXO_INTEN, 5, 1)
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FIELD(CTRL, HSTEST, 6, 1)
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REG32(INTSTATUS, 0xc)
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FIELD(INTSTATUS, TX, 0, 1)
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FIELD(INTSTATUS, RX, 1, 1)
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FIELD(INTSTATUS, TXO, 2, 1)
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FIELD(INTSTATUS, RXO, 3, 1)
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REG32(BAUDDIV, 0x10)
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REG32(PID4, 0xFD0)
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REG32(PID5, 0xFD4)
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REG32(PID6, 0xFD8)
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REG32(PID7, 0xFDC)
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REG32(PID0, 0xFE0)
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REG32(PID1, 0xFE4)
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REG32(PID2, 0xFE8)
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REG32(PID3, 0xFEC)
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REG32(CID0, 0xFF0)
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REG32(CID1, 0xFF4)
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REG32(CID2, 0xFF8)
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REG32(CID3, 0xFFC)
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/* PID/CID values */
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static const int uart_id[] = {
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0x04, 0x00, 0x00, 0x00, /* PID4..PID7 */
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0x21, 0xb8, 0x1b, 0x00, /* PID0..PID3 */
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0x0d, 0xf0, 0x05, 0xb1, /* CID0..CID3 */
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};
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static bool uart_baudrate_ok(CMSDKAPBUART *s)
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{
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/* The minimum permitted bauddiv setting is 16, so we just ignore
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* settings below that (usually this means the device has just
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* been reset and not yet programmed).
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*/
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return s->bauddiv >= 16 && s->bauddiv <= s->pclk_frq;
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}
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static void uart_update_parameters(CMSDKAPBUART *s)
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{
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QEMUSerialSetParams ssp;
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/* This UART is always 8N1 but the baud rate is programmable. */
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if (!uart_baudrate_ok(s)) {
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return;
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}
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ssp.data_bits = 8;
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ssp.parity = 'N';
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ssp.stop_bits = 1;
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ssp.speed = s->pclk_frq / s->bauddiv;
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qemu_chr_fe_ioctl(&s->chr, CHR_IOCTL_SERIAL_SET_PARAMS, &ssp);
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trace_cmsdk_apb_uart_set_params(ssp.speed);
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}
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static void cmsdk_apb_uart_update(CMSDKAPBUART *s)
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{
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/* update outbound irqs, including handling the way the rxo and txo
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* interrupt status bits are just logical AND of the overrun bit in
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* STATE and the overrun interrupt enable bit in CTRL.
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*/
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uint32_t omask = (R_INTSTATUS_RXO_MASK | R_INTSTATUS_TXO_MASK);
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s->intstatus &= ~omask;
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s->intstatus |= (s->state & (s->ctrl >> 2) & omask);
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qemu_set_irq(s->txint, !!(s->intstatus & R_INTSTATUS_TX_MASK));
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qemu_set_irq(s->rxint, !!(s->intstatus & R_INTSTATUS_RX_MASK));
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qemu_set_irq(s->txovrint, !!(s->intstatus & R_INTSTATUS_TXO_MASK));
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qemu_set_irq(s->rxovrint, !!(s->intstatus & R_INTSTATUS_RXO_MASK));
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qemu_set_irq(s->uartint, !!(s->intstatus));
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}
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static int uart_can_receive(void *opaque)
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{
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CMSDKAPBUART *s = CMSDK_APB_UART(opaque);
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/* We can take a char if RX is enabled and the buffer is empty */
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if (s->ctrl & R_CTRL_RX_EN_MASK && !(s->state & R_STATE_RXFULL_MASK)) {
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return 1;
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}
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return 0;
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}
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static void uart_receive(void *opaque, const uint8_t *buf, int size)
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{
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CMSDKAPBUART *s = CMSDK_APB_UART(opaque);
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trace_cmsdk_apb_uart_receive(*buf);
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/* In fact uart_can_receive() ensures that we can't be
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* called unless RX is enabled and the buffer is empty,
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* but we include this logic as documentation of what the
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* hardware does if a character arrives in these circumstances.
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*/
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if (!(s->ctrl & R_CTRL_RX_EN_MASK)) {
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/* Just drop the character on the floor */
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return;
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}
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if (s->state & R_STATE_RXFULL_MASK) {
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s->state |= R_STATE_RXOVERRUN_MASK;
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}
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s->rxbuf = *buf;
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s->state |= R_STATE_RXFULL_MASK;
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if (s->ctrl & R_CTRL_RX_INTEN_MASK) {
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s->intstatus |= R_INTSTATUS_RX_MASK;
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}
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cmsdk_apb_uart_update(s);
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}
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static uint64_t uart_read(void *opaque, hwaddr offset, unsigned size)
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{
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CMSDKAPBUART *s = CMSDK_APB_UART(opaque);
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uint64_t r;
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switch (offset) {
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case A_DATA:
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r = s->rxbuf;
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s->state &= ~R_STATE_RXFULL_MASK;
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cmsdk_apb_uart_update(s);
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qemu_chr_fe_accept_input(&s->chr);
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break;
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case A_STATE:
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r = s->state;
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break;
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case A_CTRL:
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r = s->ctrl;
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break;
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case A_INTSTATUS:
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r = s->intstatus;
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break;
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case A_BAUDDIV:
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r = s->bauddiv;
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break;
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case A_PID4 ... A_CID3:
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r = uart_id[(offset - A_PID4) / 4];
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break;
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default:
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qemu_log_mask(LOG_GUEST_ERROR,
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"CMSDK APB UART read: bad offset %x\n", (int) offset);
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r = 0;
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break;
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}
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trace_cmsdk_apb_uart_read(offset, r, size);
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return r;
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}
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/* Try to send tx data, and arrange to be called back later if
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* we can't (ie the char backend is busy/blocking).
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*/
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static gboolean uart_transmit(GIOChannel *chan, GIOCondition cond, void *opaque)
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{
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CMSDKAPBUART *s = CMSDK_APB_UART(opaque);
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int ret;
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s->watch_tag = 0;
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if (!(s->ctrl & R_CTRL_TX_EN_MASK) || !(s->state & R_STATE_TXFULL_MASK)) {
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return FALSE;
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}
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ret = qemu_chr_fe_write(&s->chr, &s->txbuf, 1);
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if (ret <= 0) {
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s->watch_tag = qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP,
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uart_transmit, s);
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if (!s->watch_tag) {
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/* Most common reason to be here is "no chardev backend":
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* just insta-drain the buffer, so the serial output
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* goes into a void, rather than blocking the guest.
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*/
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goto buffer_drained;
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}
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/* Transmit pending */
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trace_cmsdk_apb_uart_tx_pending();
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return FALSE;
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}
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buffer_drained:
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/* Character successfully sent */
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trace_cmsdk_apb_uart_tx(s->txbuf);
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s->state &= ~R_STATE_TXFULL_MASK;
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/* Going from TXFULL set to clear triggers the tx interrupt */
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if (s->ctrl & R_CTRL_TX_INTEN_MASK) {
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s->intstatus |= R_INTSTATUS_TX_MASK;
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}
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cmsdk_apb_uart_update(s);
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return FALSE;
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}
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static void uart_cancel_transmit(CMSDKAPBUART *s)
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{
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if (s->watch_tag) {
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g_source_remove(s->watch_tag);
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s->watch_tag = 0;
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}
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}
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static void uart_write(void *opaque, hwaddr offset, uint64_t value,
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unsigned size)
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{
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CMSDKAPBUART *s = CMSDK_APB_UART(opaque);
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trace_cmsdk_apb_uart_write(offset, value, size);
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switch (offset) {
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case A_DATA:
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s->txbuf = value;
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if (s->state & R_STATE_TXFULL_MASK) {
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/* Buffer already full -- note the overrun and let the
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* existing pending transmit callback handle the new char.
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*/
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s->state |= R_STATE_TXOVERRUN_MASK;
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cmsdk_apb_uart_update(s);
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} else {
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s->state |= R_STATE_TXFULL_MASK;
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uart_transmit(NULL, G_IO_OUT, s);
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}
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break;
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case A_STATE:
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/* Bits 0 and 1 are read only; bits 2 and 3 are W1C */
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s->state &= ~(value &
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(R_STATE_TXOVERRUN_MASK | R_STATE_RXOVERRUN_MASK));
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cmsdk_apb_uart_update(s);
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break;
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case A_CTRL:
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s->ctrl = value & 0x7f;
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if ((s->ctrl & R_CTRL_TX_EN_MASK) && !uart_baudrate_ok(s)) {
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qemu_log_mask(LOG_GUEST_ERROR,
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"CMSDK APB UART: Tx enabled with invalid baudrate\n");
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}
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cmsdk_apb_uart_update(s);
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break;
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case A_INTSTATUS:
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/* All bits are W1C. Clearing the overrun interrupt bits really
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* clears the overrun status bits in the STATE register (which
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* is then reflected into the intstatus value by the update function).
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*/
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s->state &= ~(value & (R_INTSTATUS_TXO_MASK | R_INTSTATUS_RXO_MASK));
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s->intstatus &= ~value;
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cmsdk_apb_uart_update(s);
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break;
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case A_BAUDDIV:
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s->bauddiv = value & 0xFFFFF;
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uart_update_parameters(s);
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break;
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case A_PID4 ... A_CID3:
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qemu_log_mask(LOG_GUEST_ERROR,
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"CMSDK APB UART write: write to RO offset 0x%x\n",
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(int)offset);
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break;
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default:
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qemu_log_mask(LOG_GUEST_ERROR,
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"CMSDK APB UART write: bad offset 0x%x\n", (int) offset);
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break;
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}
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}
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static const MemoryRegionOps uart_ops = {
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.read = uart_read,
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.write = uart_write,
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.endianness = DEVICE_LITTLE_ENDIAN,
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};
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static void cmsdk_apb_uart_reset(DeviceState *dev)
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{
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CMSDKAPBUART *s = CMSDK_APB_UART(dev);
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trace_cmsdk_apb_uart_reset();
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uart_cancel_transmit(s);
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s->state = 0;
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s->ctrl = 0;
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s->intstatus = 0;
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s->bauddiv = 0;
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s->txbuf = 0;
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s->rxbuf = 0;
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}
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static void cmsdk_apb_uart_init(Object *obj)
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{
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SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
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CMSDKAPBUART *s = CMSDK_APB_UART(obj);
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memory_region_init_io(&s->iomem, obj, &uart_ops, s, "uart", 0x1000);
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sysbus_init_mmio(sbd, &s->iomem);
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sysbus_init_irq(sbd, &s->txint);
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sysbus_init_irq(sbd, &s->rxint);
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sysbus_init_irq(sbd, &s->txovrint);
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sysbus_init_irq(sbd, &s->rxovrint);
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sysbus_init_irq(sbd, &s->uartint);
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}
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static void cmsdk_apb_uart_realize(DeviceState *dev, Error **errp)
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{
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CMSDKAPBUART *s = CMSDK_APB_UART(dev);
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if (s->pclk_frq == 0) {
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error_setg(errp, "CMSDK APB UART: pclk-frq property must be set");
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return;
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}
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/* This UART has no flow control, so we do not need to register
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* an event handler to deal with CHR_EVENT_BREAK.
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*/
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qemu_chr_fe_set_handlers(&s->chr, uart_can_receive, uart_receive,
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NULL, NULL, s, NULL, true);
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}
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static int cmsdk_apb_uart_post_load(void *opaque, int version_id)
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{
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CMSDKAPBUART *s = CMSDK_APB_UART(opaque);
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/* If we have a pending character, arrange to resend it. */
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if (s->state & R_STATE_TXFULL_MASK) {
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s->watch_tag = qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP,
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uart_transmit, s);
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}
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uart_update_parameters(s);
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return 0;
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}
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static const VMStateDescription cmsdk_apb_uart_vmstate = {
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.name = "cmsdk-apb-uart",
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.version_id = 1,
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.minimum_version_id = 1,
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.post_load = cmsdk_apb_uart_post_load,
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.fields = (VMStateField[]) {
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VMSTATE_UINT32(state, CMSDKAPBUART),
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VMSTATE_UINT32(ctrl, CMSDKAPBUART),
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VMSTATE_UINT32(intstatus, CMSDKAPBUART),
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VMSTATE_UINT32(bauddiv, CMSDKAPBUART),
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VMSTATE_UINT8(txbuf, CMSDKAPBUART),
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VMSTATE_UINT8(rxbuf, CMSDKAPBUART),
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VMSTATE_END_OF_LIST()
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}
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};
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static Property cmsdk_apb_uart_properties[] = {
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DEFINE_PROP_CHR("chardev", CMSDKAPBUART, chr),
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DEFINE_PROP_UINT32("pclk-frq", CMSDKAPBUART, pclk_frq, 0),
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DEFINE_PROP_END_OF_LIST(),
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};
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static void cmsdk_apb_uart_class_init(ObjectClass *klass, void *data)
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{
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DeviceClass *dc = DEVICE_CLASS(klass);
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dc->realize = cmsdk_apb_uart_realize;
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dc->vmsd = &cmsdk_apb_uart_vmstate;
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dc->reset = cmsdk_apb_uart_reset;
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dc->props = cmsdk_apb_uart_properties;
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}
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static const TypeInfo cmsdk_apb_uart_info = {
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.name = TYPE_CMSDK_APB_UART,
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.parent = TYPE_SYS_BUS_DEVICE,
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.instance_size = sizeof(CMSDKAPBUART),
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.instance_init = cmsdk_apb_uart_init,
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.class_init = cmsdk_apb_uart_class_init,
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};
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static void cmsdk_apb_uart_register_types(void)
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{
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type_register_static(&cmsdk_apb_uart_info);
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}
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type_init(cmsdk_apb_uart_register_types);
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