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 <[email protected]>
Tested-by: Daniel Palmer <[email protected]>
Reviewed-by: Simon Glass <[email protected]>

4 files changed, 142 insertions, 0 deletions

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 <[email protected]>
+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 <[email protected]>
+
+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..d3527aee112
--- /dev/null
+++ b/board/emulation/qemu-m68k/qemu-m68k.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2025, Kuan-Wei Chiu <[email protected]>
+ */
+
+#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,
+};