Re: [PATCH v4 5/6] board: Add QEMU m68k virt board support

[Heinrich Schuchardt <heinrich.schuchardt@canonical.com>]

On 1/1/26 18:54, Kuan-Wei Chiu wrote:
> Add support for the QEMU 'virt' machine on the m68k architecture. This
> board emulates a generic machine based on the Motorola 68040 CPU
> equipped with Goldfish virtual peripherals.
> 
> Introduce the necessary board configuration and initialization
> infrastructure. The implementation includes logic to parse the QEMU
> bootinfo interface, enabling dynamic detection of system RAM size to
> adapt to the virtual machine's configuration.
> 
> Enable the Goldfish TTY driver for serial console output. Additionally,
> enable Goldfish RTC and timer drivers to support real-time clock
> functionality and nanosecond-resolution delays. Include comprehensive
> documentation covering build instructions and usage examples.
> 
> Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
> Tested-by: Daniel Palmer <daniel@0x0f.com>
> ---
> No changes in v4.
> 
>   arch/m68k/Kconfig                     |   8 ++
>   board/emulation/qemu-m68k/Kconfig     |  12 +++
>   board/emulation/qemu-m68k/MAINTAINERS |   8 ++
>   board/emulation/qemu-m68k/Makefile    |   5 ++
>   board/emulation/qemu-m68k/qemu-m68k.c | 115 ++++++++++++++++++++++++++
>   configs/qemu-m68k_defconfig           |  16 ++++
>   doc/board/emulation/index.rst         |   1 +
>   doc/board/emulation/qemu-m68k.rst     |  39 +++++++++
>   include/configs/qemu-m68k.h           |  18 ++++
>   9 files changed, 222 insertions(+)
>   create mode 100644 board/emulation/qemu-m68k/Kconfig
>   create mode 100644 board/emulation/qemu-m68k/MAINTAINERS
>   create mode 100644 board/emulation/qemu-m68k/Makefile
>   create mode 100644 board/emulation/qemu-m68k/qemu-m68k.c
>   create mode 100644 configs/qemu-m68k_defconfig
>   create mode 100644 doc/board/emulation/qemu-m68k.rst
>   create mode 100644 include/configs/qemu-m68k.h
> 
> diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
> index de7c673c376..605ae5ec20c 100644
> --- a/arch/m68k/Kconfig
> +++ b/arch/m68k/Kconfig
> @@ -183,6 +183,13 @@ config TARGET_STMARK2
>           select CF_DSPI
>           select M54418
>   
> +config TARGET_QEMU_M68K
> +    bool "Support QEMU m68k virt"
> +    select M68040

Not even the dm command is available on the board by default. How about 
letting TARGET_QEMU_M68K imply CMD_DM like other targets do?

Best regards

Heinrich

> +    help
> +      This target supports the QEMU m68k virtual machine (-M virt).
> +      It simulates a Motorola 68040 CPU with Goldfish peripherals.
> +
>   endchoice
>   
>   config SYS_CPU
> @@ -208,6 +215,7 @@ source "board/freescale/m5329evb/Kconfig"
>   source "board/freescale/m5373evb/Kconfig"
>   source "board/sysam/amcore/Kconfig"
>   source "board/sysam/stmark2/Kconfig"
> +source "board/emulation/qemu-m68k/Kconfig"
>   
>   config M68K_QEMU
>   	bool "Build with workarounds for incomplete QEMU emulation"
> diff --git a/board/emulation/qemu-m68k/Kconfig b/board/emulation/qemu-m68k/Kconfig
> new file mode 100644
> index 00000000000..aae6dfe400f
> --- /dev/null
> +++ b/board/emulation/qemu-m68k/Kconfig
> @@ -0,0 +1,12 @@
> +if TARGET_QEMU_M68K
> +
> +config SYS_BOARD
> +	default "qemu-m68k"
> +
> +config SYS_VENDOR
> +	default "emulation"
> +
> +config SYS_CONFIG_NAME
> +	default "qemu-m68k"
> +
> +endif
> diff --git a/board/emulation/qemu-m68k/MAINTAINERS b/board/emulation/qemu-m68k/MAINTAINERS
> new file mode 100644
> index 00000000000..90414c58465
> --- /dev/null
> +++ b/board/emulation/qemu-m68k/MAINTAINERS
> @@ -0,0 +1,8 @@
> +QEMU M68K VIRT BOARD
> +M:	Kuan-Wei Chiu <visitorckw@gmail.com>
> +S:	Maintained
> +F:	board/emulation/qemu-m68k/
> +F:	board/emulation/common/
> +F:	include/configs/qemu-m68k.h
> +F:	configs/qemu-m68k_defconfig
> +F:	doc/board/emulation/qemu-m68k.rst
> diff --git a/board/emulation/qemu-m68k/Makefile b/board/emulation/qemu-m68k/Makefile
> new file mode 100644
> index 00000000000..5cb2886ff5a
> --- /dev/null
> +++ b/board/emulation/qemu-m68k/Makefile
> @@ -0,0 +1,5 @@
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +#
> +# Copyright (C) 2025, Kuan-Wei Chiu <visitorckw@gmail.com>
> +
> +obj-y += qemu-m68k.o
> diff --git a/board/emulation/qemu-m68k/qemu-m68k.c b/board/emulation/qemu-m68k/qemu-m68k.c
> new file mode 100644
> index 00000000000..3b911b95343
> --- /dev/null
> +++ b/board/emulation/qemu-m68k/qemu-m68k.c
> @@ -0,0 +1,115 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2025, Kuan-Wei Chiu <visitorckw@gmail.com>
> + */
> +
> +#include <asm-generic/sections.h>
> +#include <asm/bootinfo.h>
> +#include <asm/global_data.h>
> +#include <asm/io.h>
> +#include <config.h>
> +#include <dm/platdata.h>
> +#include <goldfish_rtc.h>
> +#include <goldfish_timer.h>
> +#include <goldfish_tty.h>
> +#include <init.h>
> +#include <linux/errno.h>
> +#include <serial.h>
> +
> +DECLARE_GLOBAL_DATA_PTR;
> +
> +/* QEMU Virt Machine Hardware Map */
> +#define VIRT_GF_RTC_MMIO_BASE  0xff007000
> +#define VIRT_GF_TTY_MMIO_BASE  0xff008000
> +#define VIRT_CTRL_MMIO_BASE    0xff009000
> +#define VIRT_CTRL_RESET        0x01
> +
> +/*
> + * Theoretical limit derivation:
> + * Max Bootinfo Size (Standard Page) = 4096 bytes
> + * Min Record Size (Tag + Size)      = 4 bytes
> + * Max Records = 4096 / 4 = 1024
> + */
> +#define MAX_BOOTINFO_RECORDS  1024
> +
> +int board_early_init_f(void)
> +{
> +	return 0;
> +}
> +
> +int checkboard(void)
> +{
> +	puts("Board: QEMU m68k virt\n");
> +	return 0;
> +}
> +
> +int dram_init(void)
> +{
> +	struct bi_record *record;
> +	ulong addr;
> +	int loops = 0;
> +
> +	/* Default: 16MB */
> +	gd->ram_size = 0x01000000;
> +
> +	/* QEMU places bootinfo after _end, aligned to 2 bytes */
> +	addr = (ulong)&_end;
> +	addr = ALIGN(addr, 2);
> +
> +	record = (struct bi_record *)addr;
> +
> +	if (record->tag != BI_MACHTYPE)
> +		return 0;
> +
> +	while (record->tag != BI_LAST) {
> +		if (++loops > MAX_BOOTINFO_RECORDS)
> +			panic("Bootinfo loop exceeded");
> +		if (record->tag == BI_MEMCHUNK) {
> +			gd->ram_size = record->data[1];
> +			break;
> +		}
> +		record = (struct bi_record *)((ulong)record + record->size);
> +	}
> +
> +	return 0;
> +}
> +
> +void reset_cpu(unsigned long addr)
> +{
> +	writel(VIRT_CTRL_RESET, VIRT_CTRL_MMIO_BASE);
> +	while (1)
> +		;
> +}
> +
> +int do_reset(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
> +{
> +	reset_cpu(0);
> +	return 0;
> +}
> +
> +static const struct goldfish_rtc_plat rtc_plat = {
> +	.base = (void __iomem *)VIRT_GF_RTC_MMIO_BASE,
> +};
> +
> +U_BOOT_DRVINFO(goldfish_rtc) = {
> +	.name = "rtc_goldfish",
> +	.plat = &rtc_plat,
> +};
> +
> +static const struct goldfish_timer_plat timer_plat = {
> +	.base = (void __iomem *)VIRT_GF_RTC_MMIO_BASE,
> +};
> +
> +U_BOOT_DRVINFO(goldfish_timer) = {
> +	.name = "goldfish_timer",
> +	.plat = &timer_plat,
> +};
> +
> +static const struct goldfish_tty_plat serial_plat = {
> +	.base = (void __iomem *)VIRT_GF_TTY_MMIO_BASE,
> +};
> +
> +U_BOOT_DRVINFO(goldfish_serial) = {
> +	.name = "serial_goldfish",
> +	.plat = &serial_plat,
> +};
> diff --git a/configs/qemu-m68k_defconfig b/configs/qemu-m68k_defconfig
> new file mode 100644
> index 00000000000..f9294218429
> --- /dev/null
> +++ b/configs/qemu-m68k_defconfig
> @@ -0,0 +1,16 @@
> +CONFIG_M68K=y
> +CONFIG_TEXT_BASE=0x00000000
> +CONFIG_SYS_MALLOC_LEN=0x20000
> +CONFIG_SYS_MALLOC_F_LEN=0x2000
> +CONFIG_SYS_MONITOR_LEN=262144
> +CONFIG_SYS_BOOTM_LEN=0x1000000
> +CONFIG_SYS_LOAD_ADDR=0x00000000
> +CONFIG_TARGET_QEMU_M68K=y
> +# CONFIG_DISPLAY_BOARDINFO is not set
> +CONFIG_BOARD_EARLY_INIT_F=y
> +CONFIG_DM_RTC=y
> +CONFIG_RTC_GOLDFISH=y
> +CONFIG_DM_SERIAL=y
> +CONFIG_SERIAL_GOLDFISH=y
> +CONFIG_TIMER=y
> +CONFIG_GOLDFISH_TIMER=y
> diff --git a/doc/board/emulation/index.rst b/doc/board/emulation/index.rst
> index f8908166276..4f7c812d493 100644
> --- a/doc/board/emulation/index.rst
> +++ b/doc/board/emulation/index.rst
> @@ -15,6 +15,7 @@ Emulation
>      qemu-sbsa
>      qemu-x86
>      qemu-xtensa
> +   qemu-m68k
>   
>   Also see
>   
> diff --git a/doc/board/emulation/qemu-m68k.rst b/doc/board/emulation/qemu-m68k.rst
> new file mode 100644
> index 00000000000..6c4de54cf6a
> --- /dev/null
> +++ b/doc/board/emulation/qemu-m68k.rst
> @@ -0,0 +1,39 @@
> +.. SPDX-License-Identifier: GPL-2.0-or-later
> +.. Copyright (C) 2025, Kuan-Wei Chiu <visitorckw@gmail.com>
> +
> +QEMU m68k
> +=========
> +
> +QEMU for m68k supports a special 'virt' machine designed for emulation and
> +virtualization purposes. This document describes how to run U-Boot under it.
> +
> +The QEMU virt machine models a generic m68k virtual machine with Goldfish
> +interfaces. It supports the Motorola 68040 CPU architecture.
> +
> +Building U-Boot
> +---------------
> +Set the CROSS_COMPILE environment variable to your m68k toolchain, and run:
> +
> +.. code-block:: bash
> +
> +    export CROSS_COMPILE=m68k-linux-gnu-
> +    make qemu-m68k_defconfig
> +    make
> +
> +Running U-Boot
> +--------------
> +The minimal QEMU command line to get U-Boot up and running is:
> +
> +.. code-block:: bash
> +
> +    qemu-system-m68k -M virt -cpu m68040 -nographic -kernel u-boot
> +
> +Note that the `-nographic` option is used to redirect the console to stdio,
> +which connects to the emulated Goldfish TTY device.
> +
> +Hardware Support
> +----------------
> +The following QEMU virt peripherals are supported in U-Boot:
> +
> +* Goldfish TTY (Serial Console)
> +* Goldfish RTC (Real Time Clock)
> diff --git a/include/configs/qemu-m68k.h b/include/configs/qemu-m68k.h
> new file mode 100644
> index 00000000000..1d8aa92fe80
> --- /dev/null
> +++ b/include/configs/qemu-m68k.h
> @@ -0,0 +1,18 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (C) 2025, Kuan-Wei Chiu <visitorckw@gmail.com>
> + */
> +
> +#ifndef __QEMU_M68K_H
> +#define __QEMU_M68K_H
> +
> +/* Memory Configuration */
> +#define CFG_SYS_SDRAM_BASE       0x00000000
> +
> +/*
> + * Initial Stack Pointer:
> + * Place the stack at 4MB offset to avoid overwriting U-Boot code/data.
> + */
> +#define CFG_SYS_INIT_SP_ADDR     (CFG_SYS_SDRAM_BASE + 0x400000)
> +
> +#endif /* __QEMU_M68K_H */