On Sun, 2026-09-27 at 20:13 +0000, Kuan-Wei Chiu wrote: > Add the dw8250 uart support. This hardware is a widely used 16550A > derivative that includes additional registers. > > Without this specific device support, the Linux 8250_dw driver fails > to > probe the extended registers (UCV, CPR, etc.), which are essential > for > correct feature detection. > > Signed-off-by: Kuan-Wei Chiu <[email protected]> > Reviewed-by: Chao Liu <[email protected]> > Reviewed-by: Alistair Francis <[email protected]> > --- > MAINTAINERS | 6 ++ > hw/char/Kconfig | 4 ++ > hw/char/dw8250.c | 131 > +++++++++++++++++++++++++++++++++++++++ > hw/char/meson.build | 1 + > include/hw/char/dw8250.h | 27 ++++++++ > 5 files changed, 169 insertions(+) > create mode 100644 hw/char/dw8250.c > create mode 100644 include/hw/char/dw8250.h > > diff --git a/MAINTAINERS b/MAINTAINERS > index 6be9c5725b..d4e9cf61ea 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -2848,6 +2848,12 @@ S: Maintained > F: hw/i2c/designware_i2c.c > F: include/hw/i2c/designware_i2c.h > > +DesignWare 8250 UART > +M: Kuan-Wei Chiu <[email protected]> > +S: Maintained > +F: hw/char/dw8250.c > +F: include/hw/char/dw8250.h > + > Generic Loader > M: Alistair Francis <[email protected]> > S: Maintained > diff --git a/hw/char/Kconfig b/hw/char/Kconfig > index 020c0a84bb..418d99b757 100644 > --- a/hw/char/Kconfig > +++ b/hw/char/Kconfig > @@ -95,3 +95,7 @@ config IP_OCTAL_232 > bool > default y > depends on IPACK > + > +config DW8250 > + bool > + select SERIAL
This should be SERIAL_MM as you use "serial-mm" in the driver. I'll just rename this when I apply it as SERIAL_MM selects SERIAL Alistair > diff --git a/hw/char/dw8250.c b/hw/char/dw8250.c > new file mode 100644 > index 0000000000..ccf05dd9ad > --- /dev/null > +++ b/hw/char/dw8250.c > @@ -0,0 +1,131 @@ > +/* SPDX-License-Identifier: GPL-2.0-or-later */ > +/* > + * Synopsys DesignWare APB UART (DW 8250) > + * > + * Copyright (c) 2026 Kuan-Wei Chiu <[email protected]> > + */ > + > +#include "qemu/osdep.h" > +#include "qemu/log.h" > +#include "qapi/error.h" > +#include "hw/char/dw8250.h" > +#include "hw/core/qdev-properties.h" > +#include "hw/core/qdev-properties-system.h" > + > +#define DW_UART_REGION_SIZE 0x100 > + > +#define DW_UART_RE_EN (0xB4 >> 2) /* Receiver Output Enable Register > */ > +#define DW_UART_DLF (0xC0 >> 2) /* Divisor Latch Fraction Register > */ > +#define DW_UART_CPR (0xF4 >> 2) /* Component Parameter Register */ > +#define DW_UART_UCV (0xF8 >> 2) /* UART Component Version */ > +#define DW_UART_CTR (0xFC >> 2) /* Component Type Register */ > + > +#define DW_UART_UCV_VALUE 0x3332332A /* "323*" -> v3.23a */ > +#define DW_UART_CTR_VALUE 0x44570110 /* "DW" */ > + > +static uint64_t dw8250_ext_read(void *opaque, hwaddr addr, unsigned > int size) > +{ > + DW8250State *s = opaque; > + > + switch (addr >> s->regshift) { > + case DW_UART_UCV: > + return DW_UART_UCV_VALUE; > + case DW_UART_CPR: > + return 0x00000000; /* No advanced features (DMA, extra > FIFOs) */ > + case DW_UART_CTR: > + return DW_UART_CTR_VALUE; > + > + case DW_UART_RE_EN: > + case DW_UART_DLF: > + /* > + * Return 0 to indicate these optional features > + * (RS485 and Fractional Divisor) are not implemented. > + */ > + return 0x00000000; > + > + default: > + return 0; > + } > +} > + > +static void dw8250_ext_write(void *opaque, hwaddr addr, uint64_t > val, unsigned int size) > +{ > + qemu_log_mask(LOG_UNIMP, "%s: Unimplemented write to address > 0x%" HWADDR_PRIx "\n", > + __func__, addr); > +} > + > +static const MemoryRegionOps dw8250_ext_ops = { > + .read = dw8250_ext_read, > + .write = dw8250_ext_write, > + .endianness = DEVICE_LITTLE_ENDIAN, > + .impl = { > + .min_access_size = 4, > + .max_access_size = 4, > + }, > + .valid = { > + .min_access_size = 1, > + .max_access_size = 4, > + }, > +}; > + > +static void dw8250_instance_init(Object *obj) > +{ > + DW8250State *s = DW8250(obj); > + > + s->serial_mm = qdev_new("serial-mm"); > + object_property_add_child(obj, "serial-mm", OBJECT(s- > >serial_mm)); > + object_property_add_alias(obj, "chardev", OBJECT(s->serial_mm), > "chardev"); > +} > + > +static void dw8250_realize(DeviceState *dev, Error **errp) > +{ > + DW8250State *s = DW8250(dev); > + SysBusDevice *sbd = SYS_BUS_DEVICE(dev); > + SysBusDevice *serial_sbd = SYS_BUS_DEVICE(s->serial_mm); > + > + memory_region_init(&s->container, OBJECT(dev), "dw8250- > container", > + DW_UART_REGION_SIZE); > + sysbus_init_mmio(sbd, &s->container); > + > + qdev_prop_set_uint8(s->serial_mm, "regshift", s->regshift); > + qdev_prop_set_uint8(s->serial_mm, "endianness", > DEVICE_LITTLE_ENDIAN); > + if (!sysbus_realize(serial_sbd, errp)) { > + return; > + } > + > + memory_region_init_io(&s->ext_iomem, OBJECT(dev), > &dw8250_ext_ops, s, > + "dw8250-ext", DW_UART_REGION_SIZE); > + memory_region_add_subregion(&s->container, 0, &s->ext_iomem); > + > + memory_region_add_subregion_overlap(&s->container, 0, > + > sysbus_mmio_get_region(serial_sbd, 0), 1); > + > + sysbus_pass_irq(sbd, serial_sbd); > +} > + > +static const Property dw8250_properties[] = { > + DEFINE_PROP_UINT8("regshift", DW8250State, regshift, 2), > +}; > + > +static void dw8250_class_init(ObjectClass *klass, const void *data) > +{ > + DeviceClass *dc = DEVICE_CLASS(klass); > + > + dc->realize = dw8250_realize; > + device_class_set_props(dc, dw8250_properties); > +} > + > +static const TypeInfo dw8250_info = { > + .name = TYPE_DW8250, > + .parent = TYPE_SYS_BUS_DEVICE, > + .instance_size = sizeof(DW8250State), > + .instance_init = dw8250_instance_init, > + .class_init = dw8250_class_init, > +}; > + > +static void dw8250_register_types(void) > +{ > + type_register_static(&dw8250_info); > +} > + > +type_init(dw8250_register_types) > diff --git a/hw/char/meson.build b/hw/char/meson.build > index fc3d7ee506..b2250ee6ae 100644 > --- a/hw/char/meson.build > +++ b/hw/char/meson.build > @@ -38,6 +38,7 @@ system_ss.add(when: 'CONFIG_STM32L4X5_USART', > if_true: files('stm32l4x5_usart.c' > system_ss.add(when: 'CONFIG_MCHP_PFSOC_MMUART', if_true: > files('mchp_pfsoc_mmuart.c')) > system_ss.add(when: 'CONFIG_HTIF', if_true: files('riscv_htif.c')) > system_ss.add(when: 'CONFIG_GOLDFISH_TTY', if_true: > files('goldfish_tty.c')) > +system_ss.add(when: 'CONFIG_DW8250', if_true: files('dw8250.c')) > > specific_ss.add(when: 'CONFIG_TERMINAL3270', if_true: > files('terminal3270.c')) > specific_ss.add(when: 'CONFIG_PSERIES', if_true: > files('spapr_vty.c')) > diff --git a/include/hw/char/dw8250.h b/include/hw/char/dw8250.h > new file mode 100644 > index 0000000000..59396ad202 > --- /dev/null > +++ b/include/hw/char/dw8250.h > @@ -0,0 +1,27 @@ > +/* SPDX-License-Identifier: GPL-2.0-or-later */ > +/* > + * Synopsys DesignWare APB UART (DW 8250) > + * > + * Copyright (c) 2026 Kuan-Wei Chiu <[email protected]> > + */ > + > +#ifndef HW_CHAR_DW8250_H > +#define HW_CHAR_DW8250_H > + > +#include "hw/core/sysbus.h" > +#include "qom/object.h" > + > +#define TYPE_DW8250 "dw8250" > +OBJECT_DECLARE_SIMPLE_TYPE(DW8250State, DW8250) > + > +struct DW8250State { > + SysBusDevice parent_obj; > + > + MemoryRegion container; > + MemoryRegion ext_iomem; > + DeviceState *serial_mm; > + > + uint8_t regshift; > +}; > + > +#endif
