ARM: Add a new arch + board for QEMU's 'virt' machine

This board builds an U-Boot binary that is bootable with QEMU's 'virt'
machine on ARM. The minimal QEMU command line is:

    qemu-system-arm -machine virt,highmem=off -bios u-boot.bin

(Note that the 'highmem=off' parameter to the 'virt' machine is required for
PCI to work in U-Boot.) This command line enables the following:
    - u-boot.bin loaded and executing in the emulated flash at address 0x0
    - A generated device tree blob placed at the start of RAM
    - A freely configurable amount of RAM, described by the DTB
    - A PL011 serial port, discoverable via the DTB
    - An ARMv7 architected timer
    - PSCI for rebooting the system
    - A generic ECAM-based PCI host controller, discoverable via the DTB

Additionally, QEMU allows plugging a bunch of useful peripherals to the PCI bus.
The following ones are supported by both U-Boot and Linux:

- To add a Serial ATA disk via an Intel ICH9 AHCI controller, pass e.g.:
    -drive if=none,file=disk.img,id=mydisk -device ich9-ahci,id=ahci -device ide-drive,drive=mydisk,bus=ahci.0
- To add an Intel E1000 network adapter, pass e.g.:
    -net nic,model=e1000 -net user
- To add an EHCI-compliant USB host controller, pass e.g.:
    -device usb-ehci,id=ehci
- To add a NVMe disk, pass e.g.:
    -drive if=none,file=disk.img,id=mydisk -device nvme,drive=mydisk,serial=foo

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>

arch/arm/Kconfig

@@ -631,6 +631,14 @@ config ARCH_MX5
 	select CPU_V7
 	select BOARD_EARLY_INIT_F
 
+config ARCH_QEMU
+	bool "QEMU Virtual Platform"
+	select CPU_V7
+	select ARCH_SUPPORT_PSCI
+	select DM
+	select DM_SERIAL
+	select OF_CONTROL
+
 config ARCH_RMOBILE
 	bool "Renesas ARM SoCs"
 	select DM
@@ -1171,6 +1179,8 @@ source "arch/arm/mach-rmobile/Kconfig"
 
 source "arch/arm/mach-meson/Kconfig"
 
+source "arch/arm/mach-qemu/Kconfig"
+
 source "arch/arm/mach-rockchip/Kconfig"
 
 source "arch/arm/mach-s5pc1xx/Kconfig"

arch/arm/mach-qemu/Kconfig

@@ -0,0 +1,12 @@
+if ARCH_QEMU
+
+config SYS_VENDOR
+	default "emulation"
+
+config SYS_BOARD
+	default "qemu-arm"
+
+config SYS_CONFIG_NAME
+	default "qemu-arm"
+
+endif

board/emulation/qemu-arm/MAINTAINERS

@@ -0,0 +1,6 @@
+QEMU ARM 'VIRT' BOARD
+M:	Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
+S:	Maintained
+F:	board/emulation/qemu-arm/
+F:	include/configs/qemu-arm.h
+F:	configs/qemu_arm_defconfig

board/emulation/qemu-arm/Makefile

@@ -0,0 +1,5 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+obj-y	+= qemu-arm.o

board/emulation/qemu-arm/qemu-arm.c

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2017 Tuomas Tynkkynen
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+#include <common.h>
+#include <fdtdec.h>
+
+int board_init(void)
+{
+	return 0;
+}
+
+int dram_init(void)
+{
+	if (fdtdec_setup_memory_size() != 0)
+		return -EINVAL;
+
+	return 0;
+}
+
+int dram_init_banksize(void)
+{
+	fdtdec_setup_memory_banksize();
+
+	return 0;
+}
+
+void *board_fdt_blob_setup(void)
+{
+	/* QEMU loads a generated DTB for us at the start of RAM. */
+	return (void *)CONFIG_SYS_SDRAM_BASE;
+}

configs/qemu_arm_defconfig

@@ -0,0 +1,28 @@
+CONFIG_ARM=y
+CONFIG_ARM_SMCCC=y
+CONFIG_ARCH_QEMU=y
+CONFIG_AHCI=y
+CONFIG_DISTRO_DEFAULTS=y
+# CONFIG_DISPLAY_CPUINFO is not set
+# CONFIG_DISPLAY_BOARDINFO is not set
+# CONFIG_CMD_IMLS is not set
+CONFIG_CMD_PCI=y
+CONFIG_CMD_USB=y
+CONFIG_OF_BOARD=y
+CONFIG_AHCI_PCI=y
+CONFIG_BLK=y
+# CONFIG_MMC is not set
+CONFIG_DM_ETH=y
+CONFIG_E1000=y
+CONFIG_NVME=y
+CONFIG_PCI=y
+CONFIG_DM_PCI=y
+CONFIG_PCIE_ECAM_GENERIC=y
+CONFIG_SCSI=y
+CONFIG_DM_SCSI=y
+CONFIG_SYSRESET=y
+CONFIG_SYSRESET_PSCI=y
+CONFIG_USB=y
+CONFIG_DM_USB=y
+CONFIG_USB_EHCI_HCD=y
+CONFIG_USB_EHCI_PCI=y

include/configs/qemu-arm.h

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2017 Tuomas Tynkkynen
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef __CONFIG_H
+#define __CONFIG_H
+
+#include <linux/sizes.h>
+
+/* Physical memory map */
+#define CONFIG_SYS_TEXT_BASE		0x00000000
+
+#define CONFIG_NR_DRAM_BANKS		1
+#define CONFIG_SYS_SDRAM_BASE		0x40000000
+
+/* The DTB generated by QEMU is placed at start of RAM, stay away from there */
+#define CONFIG_SYS_INIT_SP_ADDR         (CONFIG_SYS_SDRAM_BASE + SZ_2M)
+#define CONFIG_SYS_LOAD_ADDR		(CONFIG_SYS_SDRAM_BASE + SZ_2M)
+#define CONFIG_SYS_MALLOC_LEN		SZ_16M
+
+/* QEMU's PL011 serial port is detected via FDT using the device model */
+#define CONFIG_PL01X_SERIAL
+
+/* QEMU implements a 62.5MHz architected timer */
+/* FIXME: can we rely on CNTFREQ instead of hardcoding this fact here? */
+#define CONFIG_SYS_ARCH_TIMER
+#define CONFIG_SYS_HZ                       1000
+#define CONFIG_SYS_HZ_CLOCK                 62500000
+
+/* For block devices, QEMU emulates an ICH9 AHCI controller over PCI */
+#define CONFIG_SYS_SCSI_MAX_SCSI_ID 6
+#define CONFIG_SCSI_AHCI
+#define CONFIG_LIBATA
+
+/* Environment options */
+#define CONFIG_ENV_SIZE				SZ_64K
+
+#include <config_distro_defaults.h>
+
+#define BOOT_TARGET_DEVICES(func) \
+	func(SCSI, scsi, 0)
+
+#include <config_distro_bootcmd.h>
+
+#define CONFIG_PREBOOT "pci enum"
+#define CONFIG_EXTRA_ENV_SETTINGS \
+	"fdt_high=0xffffffff\0" \
+	"initrd_high=0xffffffff\0" \
+	"fdt_addr=0x40000000\0" \
+	"scriptaddr=0x40200000\0" \
+	"pxefile_addr_r=0x40300000\0" \
+	"kernel_addr_r=0x40400000\0" \
+	"ramdisk_addr_r=0x44000000\0" \
+	BOOTENV
+
+#endif /* __CONFIG_H */