On Mon, Oct 27, 2025 at 8:12 PM Michael Levit <[email protected]> wrote:
>
> From: Michael <[email protected]>
>
> Add NEORV32 UART device: CTRL/DATA registers, RX FIFO, TX to chardev.
> Includes Kconfig/meson and public header.
>
> Signed-off-by: Michael Levit <[email protected]>
>
> diff --git a/hw/char/Kconfig b/hw/char/Kconfig
> index 020c0a84bb..1fd39c2b30 100644
> --- a/hw/char/Kconfig
> +++ b/hw/char/Kconfig
> @@ -95,3 +95,6 @@ config IP_OCTAL_232
> bool
> default y
> depends on IPACK
> +
> +config NEORV32_UART
> + bool
>
> diff --git a/hw/char/meson.build b/hw/char/meson.build
> index a9e1dc26c0..2f5bf827a7 100644
> --- a/hw/char/meson.build
> +++ b/hw/char/meson.build
> @@ -31,6 +31,7 @@ system_ss.add(when: 'CONFIG_OMAP', if_true:
> files('omap_uart.c'))
> system_ss.add(when: 'CONFIG_RASPI', if_true: files('bcm2835_aux.c'))
> system_ss.add(when: 'CONFIG_RENESAS_SCI', if_true: files('renesas_sci.c'))
> system_ss.add(when: 'CONFIG_SIFIVE_UART', if_true: files('sifive_uart.c'))
> +system_ss.add(when: 'CONFIG_NEORV32_UART', if_true: files('neorv32_uart.c'))
> system_ss.add(when: 'CONFIG_SH_SCI', if_true: files('sh_serial.c'))
> system_ss.add(when: 'CONFIG_STM32F2XX_USART', if_true:
> files('stm32f2xx_usart.c'))
> system_ss.add(when: 'CONFIG_STM32L4X5_USART', if_true:
> files('stm32l4x5_usart.c'))
>
> diff --git a/hw/char/neorv32_uart.c b/hw/char/neorv32_uart.c
> new file mode 100644
> index 0000000000..b54ab54d6a
> --- /dev/null
> +++ b/hw/char/neorv32_uart.c
> @@ -0,0 +1,311 @@
> +/*
> + * Neorv32-specific UART.
> + *
> + * Copyright (c) 2025 Michael Levit
> + *
> + * Author:
> + * Michael Levit <[email protected]>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2 or later, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along
> with
> + * this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +
> +#include "qemu/osdep.h"
> +#include "qapi/error.h"
> +#include "qemu/log.h"
> +#include "migration/vmstate.h"
> +#include "chardev/char.h"
> +#include "chardev/char-fe.h"
> +#include "hw/irq.h"
> +#include "hw/char/neorv32_uart.h"
> +#include "hw/qdev-properties-system.h"
> +
> +typedef volatile struct __attribute__((packed,aligned(4))) {
> + uint32_t CTRL; /**< offset 0: control register (#NEORV32_UART_CTRL_enum)
> */
> + uint32_t DATA; /**< offset 4: data register (#NEORV32_UART_DATA_enum) */
> +} neorv32_uart_t;
This doesn't seem to be used at all
Alistair
> +
> +#define NEORV32_UART_IO_REGION_SIZE (32)
> +
> +static Property neorv32_uart_properties[] = {
> + DEFINE_PROP_CHR("chardev", Neorv32UARTState, chr),
> +};
> +
> +enum {
> + NEORV32_UART_CTRL = 0, /**< offset 0: control register */
> + NEORV32_UART_DATA = 4 /**< offset 4: data register */
> +};
> +
> +/** UART control register bits */
> +enum NEORV32_UART_CTRL_enum {
> + UART_CTRL_EN = 0, /**< UART control register(0) (r/w): UART
> global enable */
> + UART_CTRL_SIM_MODE = 1, /**< UART control register(1) (r/w):
> Simulation output override enable */
> + UART_CTRL_HWFC_EN = 2, /**< UART control register(2) (r/w): Enable
> RTS/CTS hardware flow-control */
> + UART_CTRL_PRSC_LSB = 3, /**< UART control register(3) (r/w): clock
> prescaler select, bit 0 (LSB) */
> + UART_CTRL_PRSC_MSB = 5, /**< UART control register(5) (r/w): clock
> prescaler select, bit 2 (MSB) */
> + UART_CTRL_BAUD_LSB = 6, /**< UART control register(6) (r/w): BAUD
> rate divisor, bit 0 (LSB) */
> + UART_CTRL_BAUD_MSB = 15, /**< UART control register(15) (r/w): BAUD
> rate divisor, bit 9 (MSB) */
> + UART_CTRL_RX_NEMPTY = 16, /**< UART control register(16) (r/-): RX
> FIFO not empty */
> + UART_CTRL_RX_FULL = 17, /**< UART control register(17) (r/-): RX
> FIFO full */
> + UART_CTRL_TX_EMPTY = 18, /**< UART control register(18) (r/-): TX
> FIFO empty */
> + UART_CTRL_TX_NFULL = 19, /**< UART control register(19) (r/-): TX
> FIFO not full */
> + UART_CTRL_IRQ_RX_NEMPTY = 20, /**< UART control register(20) (r/w): Fire
> IRQ if RX FIFO not empty */
> + UART_CTRL_IRQ_RX_FULL = 21, /**< UART control register(21) (r/w): Fire
> IRQ if RX FIFO full */
> + UART_CTRL_IRQ_TX_EMPTY = 22, /**< UART control register(22) (r/w): Fire
> IRQ if TX FIFO empty */
> + UART_CTRL_IRQ_TX_NFULL = 23, /**< UART control register(23) (r/w): Fire
> IRQ if TX FIFO not full */
> +
> + UART_CTRL_RX_OVER = 30, /**< UART control register(30) (r/-): RX
> FIFO overflow */
> + UART_CTRL_TX_BUSY = 31 /**< UART control register(31) (r/-):
> Transmitter busy or TX FIFO not empty */
> +};
> +
> +/** bits */
> +enum NEORV32_UART_DATA_enum {
> + UART_DATA_RTX_LSB = 0, /**< (r/w): UART rx/tx data, LSB */
> + UART_DATA_RTX_MSB = 7, /**< (r/w): UART rx/tx data, MSB */
> +
> + UART_DATA_RX_FIFO_SIZE_LSB = 8, /**< (r/-): log2(RX FIFO size), LSB */
> + UART_DATA_RX_FIFO_SIZE_MSB = 11, /**< (r/-): log2(RX FIFO size), MSB */
> +
> + UART_DATA_TX_FIFO_SIZE_LSB = 12, /**< (r/-): log2(RX FIFO size), LSB */
> + UART_DATA_TX_FIFO_SIZE_MSB = 15, /**< (r/-): log2(RX FIFO size), MSB */
> +};
> +/**@}*/
> +
> +static void neorv32_uart_update_irq(Neorv32UARTState *s)
> +{
> + int cond = 0;
> + if ((s->ie & NEORV32_UART_IE_TXWM) ||
> + ((s->ie & NEORV32_UART_IE_RXWM) && s->rx_fifo_len)) {
> + cond = 1;
> + }
> + if (cond) {
> + qemu_irq_raise(s->irq);
> + } else {
> + qemu_irq_lower(s->irq);
> + }
> +}
> +
> +static uint64_t
> +neorv32_uart_read(void *opaque, hwaddr addr, unsigned int size)
> +{
> + Neorv32UARTState *s = opaque;
> + unsigned char r;
> +
> + switch (addr) {
> + case NEORV32_UART_CTRL:
> + if (s->rx_fifo_len) {
> + s->CTRL |= (1 << UART_CTRL_RX_NEMPTY); /* set
> data available */
> + } else {
> + s->CTRL &= ~(1 << UART_CTRL_RX_NEMPTY); /*
> clear data available */
> + }
> + //TODO: assuming here TX is always avalable, fix it.
> + s->CTRL |= (1 << UART_CTRL_TX_NFULL); /* set TX not
> full */
> +
> + return s->CTRL;
> +
> + case NEORV32_UART_DATA:
> + if (s->rx_fifo_len) {
> + r = s->rx_fifo[0];
> + memmove(s->rx_fifo, s->rx_fifo + 1, s->rx_fifo_len - 1);
> + s->rx_fifo_len--;
> + qemu_chr_fe_accept_input(&s->chr);
> + s->DATA = r;
> +
> + neorv32_uart_update_irq(s); /* TODO: check if need to call */
> + return r;
> + }
> + }
> +
> +
> +
> + qemu_log_mask(LOG_GUEST_ERROR, "%s: bad read: addr=0x%x\n",
> + __func__, (int)addr);
> + return 0;
> +}
> +
> +
> +
> +static void
> +neorv32_uart_write(void *opaque, hwaddr addr,
> + uint64_t val64, unsigned int size)
> +{
> +
> + Neorv32UARTState *s = opaque;
> + uint32_t value = val64;
> + unsigned char ch = value;
> +
> + /* TODO: check if need to update data and control bits */
> + switch (addr) {
> + case NEORV32_UART_CTRL:
> + s->CTRL = value;
> + /* TODO: check if need to call, depending on IRQ flags */
> + /* neorv32_uart_update_irq(s); */
> + return;
> + case NEORV32_UART_DATA:
> + s->DATA = value;
> + qemu_chr_fe_write(&s->chr, &ch, 1);
> + /* neorv32_uart_update_irq(s); TODO: check if need to call */
> + return;
> + }
> +
> + qemu_log_mask(LOG_GUEST_ERROR, "%s: bad write: addr=0x%x v=0x%x\n",
> + __func__, (int)addr, (int)value);
> +}
> +
> +static const MemoryRegionOps neorv32_uart_ops = {
> + .read = neorv32_uart_read,
> + .write = neorv32_uart_write,
> + .endianness = DEVICE_NATIVE_ENDIAN,
> + .valid = {
> + .min_access_size = 4,
> + .max_access_size = 4
> + }
> +};
> +
> +static void neorv32_uart_init(Object *obj)
> +{
> + SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
> + Neorv32UARTState *s = NEORV32_UART(obj);
> +
> + memory_region_init_io(&s->mmio, OBJECT(s), &neorv32_uart_ops, s,
> + TYPE_NEORV32_UART, NEORV32_UART_IO_REGION_SIZE);
> + sysbus_init_mmio(sbd, &s->mmio);
> + sysbus_init_irq(sbd, &s->irq);
> +}
> +
> +
> +static void neorv32_uart_rx(void *opaque, const uint8_t *buf, int size)
> +{
> + Neorv32UARTState *s = opaque;
> +
> + /* Got a byte. */
> + if (s->rx_fifo_len >= sizeof(s->rx_fifo)) {
> + printf("WARNING: UART dropped char.\n");
> + return;
> + }
> + s->rx_fifo[s->rx_fifo_len++] = *buf;
> +
> + neorv32_uart_update_irq(s);
> +}
> +
> +static int neorv32_uart_can_rx(void *opaque)
> +{
> + Neorv32UARTState *s = opaque;
> +
> + return s->rx_fifo_len < sizeof(s->rx_fifo);
> +}
> +
> +static void neorv32_uart_event(void *opaque, QEMUChrEvent event)
> +{
> +}
> +
> +static int neorv32_uart_be_change(void *opaque)
> +{
> + Neorv32UARTState *s = opaque;
> +
> + qemu_chr_fe_set_handlers(&s->chr, neorv32_uart_can_rx, neorv32_uart_rx,
> + neorv32_uart_event, neorv32_uart_be_change, s,
> + NULL, true);
> +
> + return 0;
> +}
> +
> +static void neorv32_uart_realize(DeviceState *dev, Error **errp)
> +{
> + Neorv32UARTState *s = NEORV32_UART(dev);
> +
> + qemu_chr_fe_set_handlers(&s->chr, neorv32_uart_can_rx, neorv32_uart_rx,
> + neorv32_uart_event, neorv32_uart_be_change, s,
> + NULL, true);
> +
> +}
> +
> +static const VMStateDescription vmstate_neorv32_uart = {
> + .name = TYPE_NEORV32_UART,
> + .version_id = 1,
> + .minimum_version_id = 1,
> + .fields = (VMStateField[]) {
> + VMSTATE_UINT8_ARRAY(rx_fifo,
> + Neorv32UARTState,
> + NEORV32_UART_RX_FIFO_SIZE),
> + VMSTATE_UINT8(rx_fifo_len, Neorv32UARTState),
> + VMSTATE_UINT32(ie, Neorv32UARTState),
> + VMSTATE_END_OF_LIST()
> + },
> +};
> +
> +static void neorv32_uart_reset_enter(Object *obj, ResetType type)
> +{
> + Neorv32UARTState *s = NEORV32_UART(obj);
> + s->rx_fifo_len = 0;
> + s->ie = 0;
> +}
> +
> +static void neorv32_uart_reset_hold(Object *obj, ResetType type)
> +{
> + Neorv32UARTState *s = NEORV32_UART(obj);
> + qemu_irq_lower(s->irq);
> +}
> +
> +static void neorv32_uart_class_init(ObjectClass *oc,const void *data)
> +{
> + DeviceClass *dc = DEVICE_CLASS(oc);
> + ResettableClass *rc = RESETTABLE_CLASS(oc);
> +
> + dc->realize = neorv32_uart_realize;
> + dc->vmsd = &vmstate_neorv32_uart;
> + rc->phases.enter = neorv32_uart_reset_enter;
> + rc->phases.hold = neorv32_uart_reset_hold;
> + device_class_set_props(dc, neorv32_uart_properties);
> + set_bit(DEVICE_CATEGORY_INPUT, dc->categories);
> +}
> +
> +static const TypeInfo neorv32_uart_info = {
> + .name = TYPE_NEORV32_UART,
> + .parent = TYPE_SYS_BUS_DEVICE,
> + .instance_size = sizeof(Neorv32UARTState),
> + .instance_init = neorv32_uart_init,
> + .class_init = neorv32_uart_class_init,
> +};
> +
> +static void neorv32_uart_register_types(void)
> +{
> + type_register_static(&neorv32_uart_info);
> +}
> +
> +type_init(neorv32_uart_register_types)
> +/*
> + * Create UART device.
> + */
> +Neorv32UARTState *neorv32_uart_create(MemoryRegion *address_space,
> + hwaddr base,
> + Chardev *chr)
> +{
> + DeviceState *dev;
> + SysBusDevice *s;
> + bool succed= false;
> +
> + dev = qdev_new("riscv.neorv32.uart");
> +
> + qdev_prop_set_chr(dev, "chardev", chr);
> + s = SYS_BUS_DEVICE(dev);
> + succed = sysbus_realize_and_unref(s, &error_fatal);
> +
> + if (succed) {
> + memory_region_add_subregion(address_space, base,
> + sysbus_mmio_get_region(s, 0));
> + return NEORV32_UART(dev);
> + } else {
> + return NULL;
> + }
> +} //neorv32_uart_create
>
> diff --git a/include/hw/char/neorv32_uart.h b/include/hw/char/neorv32_uart.h
> new file mode 100644
> index 0000000000..3651d4741f
> --- /dev/null
> +++ b/include/hw/char/neorv32_uart.h
> @@ -0,0 +1,68 @@
> +/*
> + * Neorv32-specific UART.
> + *
> + * Copyright (c) 2025 Michael Levit
> + *
> + * Author:
> + * Michael Levit <[email protected]>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2 or later, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along
> with
> + * this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#ifndef HW_NEORV32_UART_H
> +#define HW_NEORV32_UART_H
> +
> +#include "chardev/char-fe.h"
> +#include "hw/qdev-properties.h"
> +#include "hw/sysbus.h"
> +#include "qom/object.h"
> +
> +#define TYPE_NEORV32_UART "riscv.neorv32.uart"
> +OBJECT_DECLARE_SIMPLE_TYPE(Neorv32UARTState, NEORV32_UART)
> +
> +#define QEMU_UART_DATA_RX_FIFO_SIZE_LSB 8 /**256 < UART data register(8)
> (r/-): log2(RX FIFO size), LSB */
> +#define QEMU_UART_DATA_RX_FIFO_SIZE_MSB 11 /** 2048 < UART data
> register(11) (r/-): log2(RX FIFO size), MSB */
> +
> +#define NEORV32_UART_RX_FIFO_SIZE 32 //in HW it is 2048 + 256 = _MSB + _LSB
> +
> +enum {
> + NEORV32_UART_IE_TXWM = 1, /* Transmit watermark interrupt
> enable */
> + NEORV32_UART_IE_RXWM = 2 /* Receive watermark interrupt enable
> */
> +};
> +
> +enum {
> + NEORV32_UART_IP_TXWM = 1, /* Transmit watermark interrupt
> pending */
> + NEORV32_UART_IP_RXWM = 2 /* Receive watermark interrupt
> pending */
> +};
> +
> +
> +
> +struct Neorv32UARTState {
> + /*< private >*/
> + SysBusDevice parent_obj;
> +
> + /*< public >*/
> + qemu_irq irq;
> + MemoryRegion mmio;
> + CharBackend chr;
> + uint8_t rx_fifo[NEORV32_UART_RX_FIFO_SIZE];
> + uint8_t rx_fifo_len;
> + uint32_t ie; //interrupt enable
> + uint32_t CTRL;
> + uint32_t DATA;
> +};
> +
> +Neorv32UARTState *neorv32_uart_create(MemoryRegion *address_space, hwaddr
> base,
> + Chardev *chr);
> +
> +#endif //HW_NEORV32_UART_H
>
