On Thu, May 14, 2026 at 01:15:24AM +0800, 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: > > [ 0.293566] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled > [ 0.306929] Oops - store (or AMO) access fault [#1] > [ 0.307020] Modules linked in: > [ 0.307192] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.0.0 #1 > PREEMPTLAZY > [ 0.307250] Hardware name: Milk-V Duo (DT) > [ 0.307294] epc : dw8250_setup_port+0x22/0x520 > [ 0.307504] ra : dw8250_probe+0x57e/0x5b8 > [ 0.307518] epc : ffffffff80708dd6 ra : ffffffff8070a49e sp : > ffffffc60000b820 > [ 0.307525] gp : ffffffff81a32ba8 tp : ffffffd602180cc0 t0 : > 0000000000000073 > [ 0.307533] t1 : 000000000000006c t2 : 0000000000000000 s0 : > ffffffc60000b830 > [ 0.307539] s1 : ffffffd6028c8640 a0 : ffffffc60000b848 a1 : > ffffffff813162c1 > [ 0.307546] a2 : ffffffff813162c0 a3 : ffffffd6028c8640 a4 : > ffffffc60002d0b4 > [ 0.307552] a5 : 0000000000000001 a6 : 0000000000000094 a7 : > 0000000000000060 > [ 0.307558] s2 : ffffffd60225d410 s3 : ffffffd60225d400 s4 : > 0000000000000000 > [ 0.307573] s5 : ffffffff80e31a48 s6 : 0000000000000008 s7 : > 0000000000000000 > [ 0.307584] s8 : 0000000000000149 s9 : 0000000000000000 s10: > 0000000000000000 > [ 0.307590] s11: 0000000000000000 t3 : ffffffd602007c00 t4 : > ffffffff81601540 > [ 0.307604] t5 : 0000000000000003 t6 : ffffffd602a42f82 ssp : > 0000000000000000 > [ 0.307611] status: 0000000200000120 badaddr: ffffffc60002d0b4 cause: > 0000000000000007 > [ 0.307652] [<ffffffff80708dd6>] dw8250_setup_port+0x22/0x520 > [ 0.307695] [<ffffffff8070a49e>] dw8250_probe+0x57e/0x5b8 > [ 0.307702] [<ffffffff80731f0e>] platform_probe+0x46/0x80 > [ 0.307708] [<ffffffff8072f67c>] really_probe+0x84/0x22c > [ 0.307715] [<ffffffff8072f880>] __driver_probe_device+0x5c/0xd4 > [ 0.307721] [<ffffffff8072f9be>] driver_probe_device+0x2e/0xf4 > [ 0.307727] [<ffffffff8072fbe6>] __driver_attach+0x6e/0x14c > [ 0.307734] [<ffffffff8072d5f0>] bus_for_each_dev+0x60/0xb0 > [ 0.307740] [<ffffffff8072f1b2>] driver_attach+0x1a/0x24 > [ 0.307746] [<ffffffff8072e8da>] bus_add_driver+0xca/0x1d8 > [ 0.307752] [<ffffffff80730aaa>] driver_register+0x3e/0xdc > [ 0.307757] [<ffffffff80731c54>] __platform_driver_register+0x1c/0x24 > [ 0.307779] [<ffffffff80c334f6>] dw8250_platform_driver_init+0x1a/0x24 > [ 0.307793] [<ffffffff80011992>] do_one_initcall+0x4e/0x2a4 > [ 0.307800] [<ffffffff80c01362>] kernel_init_freeable+0x226/0x2b0 > [ 0.307807] [<ffffffff80bc3798>] kernel_init+0x1c/0x144 > [ 0.307813] [<ffffffff8001361c>] ret_from_fork_kernel+0x18/0x164 > [ 0.307820] [<ffffffff80bcefb6>] ret_from_fork_kernel_asm+0x16/0x18 > [ 0.307914] Code: 3683 2085 0b63 32f7 000f 0140 6918 4785 0713 0b47 (c31c) > 2583 > [ 0.308041] ---[ end trace 0000000000000000 ]--- > [ 0.308180] Kernel panic - not syncing: Fatal exception in interrupt > [ 0.315760] ---[ end Kernel panic - not syncing: Fatal exception in > interrupt ]--- > > Signed-off-by: Kuan-Wei Chiu <[email protected]> Reviewed-by: Chao Liu <[email protected]>
Thanks, Chao > --- > hw/char/Kconfig | 4 ++ > hw/char/dw8250.c | 118 +++++++++++++++++++++++++++++++++++++++ > hw/char/meson.build | 1 + > include/hw/char/dw8250.h | 27 +++++++++ > 4 files changed, 150 insertions(+) > create mode 100644 hw/char/dw8250.c > create mode 100644 include/hw/char/dw8250.h > > 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 > diff --git a/hw/char/dw8250.c b/hw/char/dw8250.c > new file mode 100644 > index 0000000000..4ec829ceaf > --- /dev/null > +++ b/hw/char/dw8250.c > @@ -0,0 +1,118 @@ > +/* 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 "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 /* Receiver Output Enable Register */ > +#define DW_UART_DLF 0xC0 /* Divisor Latch Fraction Register */ > +#define DW_UART_CPR 0xF4 /* Component Parameter Register */ > +#define DW_UART_UCV 0xF8 /* UART Component Version */ > +#define DW_UART_CTR 0xFC /* 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) > +{ > + switch (addr) { > + 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) > +{ > +} > + > +static const MemoryRegionOps dw8250_ext_ops = { > + .read = dw8250_ext_read, > + .write = dw8250_ext_write, > + .endianness = DEVICE_LITTLE_ENDIAN, > + .valid.min_access_size = 4, > + .valid.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); > + sysbus_realize(serial_sbd, errp); > + > + 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 > -- > 2.54.0.563.g4f69b47b94-goog >
