/*
* AVR USART
*
* Copyright (c) 2018 University of Kent
* Author: Sarah Harris
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see
* <http://www.gnu.org/licenses/lgpl-2.1.html>
*/
#include "qemu/osdep.h"
#include "hw/char/avr_usart.h"
#include "qemu/log.h"
#include "hw/irq.h"
#include "hw/qdev-properties.h"
static int avr_usart_can_receive(void *opaque)
{
AVRUsartState *usart = opaque;
if (usart->data_valid || !(usart->csrb & USART_CSRB_RXEN)) {
return 0;
}
return 1;
}
static void avr_usart_receive(void *opaque, const uint8_t *buffer, int size)
{
AVRUsartState *usart = opaque;
assert(size == 1);
assert(!usart->data_valid);
usart->data = buffer[0];
usart->data_valid = true;
usart->csra |= USART_CSRA_RXC;
if (usart->csrb & USART_CSRB_RXCIE) {
qemu_set_irq(usart->rxc_irq, 1);
}
}
static void update_char_mask(AVRUsartState *usart)
{
uint8_t mode = ((usart->csrc & USART_CSRC_CSZ0) ? 1 : 0) |
((usart->csrc & USART_CSRC_CSZ1) ? 2 : 0) |
((usart->csrb & USART_CSRB_CSZ2) ? 4 : 0);
switch (mode) {
case 0:
usart->char_mask = 0b11111;
break;
case 1:
usart->char_mask = 0b111111;
break;
case 2:
usart->char_mask = 0b1111111;
break;
case 3:
usart->char_mask = 0b11111111;
break;
case 4:
/* Fallthrough. */
case 5:
/* Fallthrough. */
case 6:
qemu_log_mask(
LOG_GUEST_ERROR,
"%s: Reserved character size 0x%x\n",
__func__,
mode);
break;
case 7:
qemu_log_mask(
LOG_GUEST_ERROR,
"%s: Nine bit character size not supported (forcing eight)\n",
__func__);
usart->char_mask = 0b11111111;
break;
default:
assert(0);
}
}
static void avr_usart_reset(DeviceState *dev)
{
AVRUsartState *usart = AVR_USART(dev);
usart->data_valid = false;
usart->csra = 0b00100000;
usart->csrb = 0b00000000;
usart->csrc = 0b00000110;
usart->brrl = 0;
usart->brrh = 0;
update_char_mask(usart);
qemu_set_irq(usart->rxc_irq, 0);
qemu_set_irq(usart->txc_irq, 0);
qemu_set_irq(usart->dre_irq, 0);
}
static uint64_t avr_usart_read(void *opaque, hwaddr addr, unsigned int size)
{
AVRUsartState *usart = opaque;
uint8_t data;
assert(size == 1);
if (!usart->enabled) {
return 0;
}
switch (addr) {
case USART_DR:
if (!(usart->csrb & USART_CSRB_RXEN)) {
/* Receiver disabled, ignore. */
return 0;
}
if (usart->data_valid) {
data = usart->data & usart->char_mask;
usart->data_valid = false;
} else {
data = 0;
}
usart->csra &= 0xff ^ USART_CSRA_RXC;
qemu_set_irq(usart->rxc_irq, 0);
qemu_chr_fe_accept_input(&usart->chr);
return data;
case USART_CSRA:
return usart->csra;
case USART_CSRB:
return usart->csrb;
case USART_CSRC:
return usart->csrc;
case USART_BRRL:
return usart->brrl;
case USART_BRRH:
return usart->brrh;
default:
qemu_log_mask(
LOG_GUEST_ERROR,
"%s: Bad offset 0x%"HWADDR_PRIx"\n",
__func__,
addr);
}
return 0;
}
static void avr_usart_write(void *opaque, hwaddr addr, uint64_t value,
unsigned int size)
{
AVRUsartState *usart = opaque;
uint8_t mask;
uint8_t data;
assert((value & 0xff) == value);
assert(size == 1);
if (!usart->enabled) {
return;
}
switch (addr) {
case USART_DR:
if (!(usart->csrb & USART_CSRB_TXEN)) {
/* Transmitter disabled, ignore. */
return;
}
usart->csra |= USART_CSRA_TXC;
usart->csra |= USART_CSRA_DRE;
if (usart->csrb & USART_CSRB_TXCIE) {
qemu_set_irq(usart->txc_irq, 1);
usart->csra &= 0xff ^ USART_CSRA_TXC;
}
if (usart->csrb & USART_CSRB_DREIE) {
qemu_set_irq(usart->dre_irq, 1);
}
data = value;
qemu_chr_fe_write_all(&usart->chr, &data, 1);
break;
case USART_CSRA:
mask = 0b01000011;
/* Mask read-only bits. */
value = (value & mask) | (usart->csra & (0xff ^ mask));
usart->csra = value;
if (value & USART_CSRA_TXC) {
usart->csra ^= USART_CSRA_TXC;
qemu_set_irq(usart->txc_irq, 0);
}
if (value & USART_CSRA_MPCM) {
qemu_log_mask(
LOG_GUEST_ERROR,
"%s: MPCM not supported by USART\n",
__func__);
}
break;
case USART_CSRB:
mask = 0b11111101;
/* Mask read-only bits. */
value = (value & mask) | (usart->csrb & (0xff ^ mask));
usart->csrb = value;
if (!(value & USART_CSRB_RXEN)) {
/* Receiver disabled, flush input buffer. */
usart->data_valid = false;
}
qemu_set_irq(usart->rxc_irq,
((value & USART_CSRB_RXCIE) &&
(usart->csra & USART_CSRA_RXC)) ? 1 : 0);
qemu_set_irq(usart->txc_irq,
((value & USART_CSRB_TXCIE) &&
(usart->csra & USART_CSRA_TXC)) ? 1 : 0);
qemu_set_irq(usart->dre_irq,
((value & USART_CSRB_DREIE) &&
(usart->csra & USART_CSRA_DRE)) ? 1 : 0);
update_char_mask(usart);
break;
case USART_CSRC:
usart->csrc = value;
if ((value & USART_CSRC_MSEL1) && (value & USART_CSRC_MSEL0)) {
qemu_log_mask(
LOG_GUEST_ERROR,
"%s: SPI mode not supported by USART\n",
__func__);
}
if ((value & USART_CSRC_MSEL1) && !(value & USART_CSRC_MSEL0)) {
qemu_log_mask(LOG_GUEST_ERROR, "%s: Bad USART mode\n", __func__);
}
if (!(value & USART_CSRC_PM1) && (value & USART_CSRC_PM0)) {
qemu_log_mask(
LOG_GUEST_ERROR,
"%s: Bad USART parity mode\n",
__func__);
}
update_char_mask(usart);
break;
case USART_BRRL:
usart->brrl = value;
break;
case USART_BRRH:
usart->brrh = value & 0b00001111;
break;
default:
qemu_log_mask(
LOG_GUEST_ERROR,
"%s: Bad offset 0x%"HWADDR_PRIx"\n",
__func__,
addr);
}
}
static const MemoryRegionOps avr_usart_ops = {
.read = avr_usart_read,
.write = avr_usart_write,
.endianness = DEVICE_NATIVE_ENDIAN,
.impl = {.min_access_size = 1, .max_access_size = 1}
};
static Property avr_usart_properties[] = {
DEFINE_PROP_CHR("chardev", AVRUsartState, chr),
DEFINE_PROP_END_OF_LIST(),
};
static void avr_usart_pr(void *opaque, int irq, int level)
{
AVRUsartState *s = AVR_USART(opaque);
s->enabled = !level;
if (!s->enabled) {
avr_usart_reset(DEVICE(s));
}
}
static void avr_usart_init(Object *obj)
{
AVRUsartState *s = AVR_USART(obj);
sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->rxc_irq);
sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->dre_irq);
sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->txc_irq);
memory_region_init_io(&s->mmio, obj, &avr_usart_ops, s, TYPE_AVR_USART, 7);
sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->mmio);
qdev_init_gpio_in(DEVICE(s), avr_usart_pr, 1);
s->enabled = true;
}
static void avr_usart_realize(DeviceState *dev, Error **errp)
{
AVRUsartState *s = AVR_USART(dev);
qemu_chr_fe_set_handlers(&s->chr, avr_usart_can_receive,
avr_usart_receive, NULL, NULL,
s, NULL, true);
avr_usart_reset(dev);
}
static void avr_usart_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
dc->reset = avr_usart_reset;
device_class_set_props(dc, avr_usart_properties);
dc->realize = avr_usart_realize;
}
static const TypeInfo avr_usart_info = {
.name = TYPE_AVR_USART,
.parent = TYPE_SYS_BUS_DEVICE,
.instance_size = sizeof(AVRUsartState),
.instance_init = avr_usart_init,
.class_init = avr_usart_class_init,
};
static void avr_usart_register_types(void)
{
type_register_static(&avr_usart_info);
}
type_init(avr_usart_register_types)
