board: Add QEMU m68k virt board support

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> Reviewed-by: Simon Glass <simon.glass@canonical.com>
2026-02-02 14:24:41 -06:00
parent c69b6aeaa3
commit 516afc8f76
9 changed files with 229 additions and 0 deletions
@@ -194,6 +194,14 @@ config TARGET_STMARK2
        select CF_DSPI
        select M54418

+config TARGET_QEMU_M68K
+    bool "Support QEMU m68k virt"
+    select M68040
+    imply CMD_DM
+    help
+      This target supports the QEMU m68k virtual machine (-M virt).
+      It simulates a Motorola 68040 CPU with Goldfish peripherals.
+
 endchoice

 config SYS_CPU
@@ -222,6 +230,7 @@ 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"
@@ -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
@@ -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
@@ -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
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2025, Kuan-Wei Chiu <visitorckw@gmail.com>
+ */
+
+#include <config.h>
+#include <goldfish_rtc.h>
+#include <goldfish_timer.h>
+#include <goldfish_tty.h>
+#include <init.h>
+#include <qemu_virt_ctrl.h>
+#include <serial.h>
+#include <asm-generic/sections.h>
+#include <asm/bootinfo.h>
+#include <asm/global_data.h>
+#include <asm/io.h>
+#include <dm/platdata.h>
+#include <linux/errno.h>
+#include <linux/sizes.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+static struct goldfish_tty_plat serial_plat;
+static struct goldfish_rtc_plat rtc_plat;
+static struct goldfish_timer_plat timer_plat;
+static struct qemu_virt_ctrl_plat reset_plat;
+
+/*
+ * 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
+
+static void parse_bootinfo(void)
+{
+	struct bi_record *record;
+	ulong addr;
+	int loops = 0;
+
+	/* 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;
+
+	while (record->tag != BI_LAST) {
+		phys_addr_t base = record->data[0];
+
+		if (++loops > MAX_BOOTINFO_RECORDS)
+			panic("Bootinfo loop exceeded");
+
+		switch (record->tag) {
+		case BI_VIRT_GF_TTY_BASE:
+			serial_plat.reg = base;
+			break;
+		case BI_VIRT_GF_RTC_BASE:
+			rtc_plat.reg = base;
+			timer_plat.reg = base;
+			break;
+		case BI_VIRT_CTRL_BASE:
+			reset_plat.reg = base;
+			break;
+		case BI_MEMCHUNK:
+			gd->ram_size = record->data[1];
+			break;
+		}
+		record = (struct bi_record *)((ulong)record + record->size);
+	}
+}
+
+int board_early_init_f(void)
+{
+	parse_bootinfo();
+
+	return 0;
+}
+
+int checkboard(void)
+{
+	puts("Board: QEMU m68k virt\n");
+
+	return 0;
+}
+
+int dram_init(void)
+{
+	/* Default: 16MB */
+	if (!gd->ram_size)
+		gd->ram_size = SZ_16M;
+
+	return 0;
+}
+
+U_BOOT_DRVINFO(goldfish_rtc) = {
+	.name = "rtc_goldfish",
+	.plat = &rtc_plat,
+};
+
+U_BOOT_DRVINFO(goldfish_timer) = {
+	.name = "goldfish_timer",
+	.plat = &timer_plat,
+};
+
+U_BOOT_DRVINFO(goldfish_serial) = {
+	.name = "serial_goldfish",
+	.plat = &serial_plat,
+};
+
+U_BOOT_DRVINFO(sysreset_qemu_virt_ctrl) = {
+	.name = "sysreset_qemu_virt_ctrl",
+	.plat = &reset_plat,
+};
@@ -0,0 +1,20 @@
+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_CMD_POWEROFF=y
+CONFIG_DM_RTC=y
+CONFIG_RTC_GOLDFISH=y
+CONFIG_DM_SERIAL=y
+CONFIG_SERIAL_GOLDFISH=y
+CONFIG_SYSRESET=y
+CONFIG_SYSRESET_CMD_POWEROFF=y
+CONFIG_SYSRESET_QEMU_VIRT_CTRL=y
+CONFIG_TIMER=y
+CONFIG_GOLDFISH_TIMER=y
@@ -15,6 +15,7 @@ Emulation
   qemu-sbsa
   qemu-x86
   qemu-xtensa
+   qemu-m68k

 Also see

@@ -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)
@@ -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 */