[PATCH] mips: add support for Qemu system architecture

Add support for the virtual MIPS system that is emulated by Qemu.  See
http://www.linux-mips.org/wiki/Qemu for a detailed current status.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/mips/Kconfig

@@ -445,6 +445,24 @@ config DDB5477_BUS_FREQUENCY
 	depends on DDB5477
 	default 0
 
+config QEMU
+	bool "Support for Qemu"
+	select DMA_COHERENT
+	select GENERIC_ISA_DMA
+	select HAVE_STD_PC_SERIAL_PORT
+	select I8259
+	select ISA
+	select SWAP_IO_SPACE
+	select SYS_SUPPORTS_32BIT_KERNEL
+	select SYS_SUPPORTS_BIG_ENDIAN
+	help
+	 Qemu is a software emulator which among other architectures also
+	 can simulate a MIPS32 4Kc system.  This patch adds support for the
+	 system architecture that currently is being simulated by Qemu.  It
+	 will eventually be removed again when Qemu has the capability to
+	 simulate actual MIPS hardware platforms.  More information on Qemu
+	 can be found at http://www.linux-mips.org/wiki/Qemu.
+
 config SGI_IP22
 	bool "Support for SGI IP22 (Indy/Indigo2)"
 	select ARC

arch/mips/Makefile

@@ -423,6 +423,12 @@ core-$(CONFIG_PMC_YOSEMITE)	+= arch/mips/pmc-sierra/yosemite/
 cflags-$(CONFIG_PMC_YOSEMITE)	+= -Iinclude/asm-mips/mach-yosemite
 load-$(CONFIG_PMC_YOSEMITE)	+= 0xffffffff80100000
 
+# Qemu simulating MIPS32 4Kc
+#
+core-$(CONFIG_QEMU)		+= arch/mips/qemu/
+cflags-$(CONFIG_QEMU)		+= -Iinclude/asm-mips/mach-qemu
+load-$(CONFIG_QEMU)		+= 0xffffffff80010000
+
 #
 # Momentum Ocelot-3
 #

arch/mips/configs/qemu_defconfig

+#
+# Automatically generated make config: don't edit
+# Linux kernel version: 2.6.13-rc6
+# Mon Aug  8 11:49:54 2005
+#
+CONFIG_MIPS=y
+
+#
+# Code maturity level options
+#
+# CONFIG_EXPERIMENTAL is not set
+CONFIG_CLEAN_COMPILE=y
+CONFIG_BROKEN_ON_SMP=y
+CONFIG_INIT_ENV_ARG_LIMIT=32
+
+#
+# General setup
+#
+CONFIG_LOCALVERSION=""
+# CONFIG_SWAP is not set
+# CONFIG_SYSVIPC is not set
+# CONFIG_BSD_PROCESS_ACCT is not set
+# CONFIG_SYSCTL is not set
+# CONFIG_AUDIT is not set
+# CONFIG_HOTPLUG is not set
+CONFIG_KOBJECT_UEVENT=y
+# CONFIG_IKCONFIG is not set
+CONFIG_EMBEDDED=y
+CONFIG_KALLSYMS=y
+# CONFIG_KALLSYMS_EXTRA_PASS is not set
+CONFIG_PRINTK=y
+# CONFIG_BUG is not set
+# CONFIG_BASE_FULL is not set
+# CONFIG_FUTEX is not set
+# CONFIG_EPOLL is not set
+# CONFIG_CC_OPTIMIZE_FOR_SIZE is not set
+# CONFIG_SHMEM is not set
+CONFIG_CC_ALIGN_FUNCTIONS=0
+CONFIG_CC_ALIGN_LABELS=0
+CONFIG_CC_ALIGN_LOOPS=0
+CONFIG_CC_ALIGN_JUMPS=0
+CONFIG_TINY_SHMEM=y
+CONFIG_BASE_SMALL=1
+
+#
+# Loadable module support
+#
+# CONFIG_MODULES is not set
+
+#
+# Machine selection
+#
+# CONFIG_MIPS_MTX1 is not set
+# CONFIG_MIPS_BOSPORUS is not set
+# CONFIG_MIPS_PB1000 is not set
+# CONFIG_MIPS_PB1100 is not set
+# CONFIG_MIPS_PB1500 is not set
+# CONFIG_MIPS_PB1550 is not set
+# CONFIG_MIPS_PB1200 is not set
+# CONFIG_MIPS_DB1000 is not set
+# CONFIG_MIPS_DB1100 is not set
+# CONFIG_MIPS_DB1500 is not set
+# CONFIG_MIPS_DB1550 is not set
+# CONFIG_MIPS_DB1200 is not set
+# CONFIG_MIPS_MIRAGE is not set
+# CONFIG_MIPS_COBALT is not set
+# CONFIG_MACH_DECSTATION is not set
+# CONFIG_MIPS_EV64120 is not set
+# CONFIG_MIPS_EV96100 is not set
+# CONFIG_MIPS_IVR is not set
+# CONFIG_MIPS_ITE8172 is not set
+# CONFIG_MACH_JAZZ is not set
+# CONFIG_LASAT is not set
+# CONFIG_MIPS_ATLAS is not set
+# CONFIG_MIPS_MALTA is not set
+# CONFIG_MIPS_SEAD is not set
+# CONFIG_MOMENCO_JAGUAR_ATX is not set
+# CONFIG_MOMENCO_OCELOT is not set
+# CONFIG_MOMENCO_OCELOT_3 is not set
+# CONFIG_MOMENCO_OCELOT_C is not set
+# CONFIG_MOMENCO_OCELOT_G is not set
+# CONFIG_MIPS_XXS1500 is not set
+# CONFIG_PNX8550_V2PCI is not set
+# CONFIG_PNX8550_JBS is not set
+# CONFIG_DDB5074 is not set
+# CONFIG_DDB5476 is not set
+# CONFIG_DDB5477 is not set
+# CONFIG_MACH_VR41XX is not set
+# CONFIG_PMC_YOSEMITE is not set
+CONFIG_QEMU=y
+# CONFIG_SGI_IP22 is not set
+# CONFIG_SGI_IP27 is not set
+# CONFIG_SGI_IP32 is not set
+# CONFIG_SIBYTE_SWARM is not set
+# CONFIG_SIBYTE_SENTOSA is not set
+# CONFIG_SIBYTE_RHONE is not set
+# CONFIG_SIBYTE_CARMEL is not set
+# CONFIG_SIBYTE_PTSWARM is not set
+# CONFIG_SIBYTE_LITTLESUR is not set
+# CONFIG_SIBYTE_CRHINE is not set
+# CONFIG_SIBYTE_CRHONE is not set
+# CONFIG_SNI_RM200_PCI is not set
+# CONFIG_TOSHIBA_JMR3927 is not set
+# CONFIG_TOSHIBA_RBTX4927 is not set
+# CONFIG_TOSHIBA_RBTX4938 is not set
+CONFIG_RWSEM_GENERIC_SPINLOCK=y
+CONFIG_GENERIC_CALIBRATE_DELAY=y
+CONFIG_HAVE_DEC_LOCK=y
+CONFIG_DMA_COHERENT=y
+CONFIG_GENERIC_ISA_DMA=y
+CONFIG_I8259=y
+CONFIG_CPU_BIG_ENDIAN=y
+# CONFIG_CPU_LITTLE_ENDIAN is not set
+CONFIG_SYS_SUPPORTS_BIG_ENDIAN=y
+CONFIG_SWAP_IO_SPACE=y
+CONFIG_MIPS_L1_CACHE_SHIFT=5
+CONFIG_HAVE_STD_PC_SERIAL_PORT=y
+
+#
+# CPU selection
+#
+# CONFIG_CPU_MIPS32_R1 is not set
+# CONFIG_CPU_MIPS32_R2 is not set
+# CONFIG_CPU_MIPS64_R1 is not set
+# CONFIG_CPU_MIPS64_R2 is not set
+# CONFIG_CPU_R3000 is not set
+# CONFIG_CPU_TX39XX is not set
+# CONFIG_CPU_VR41XX is not set
+# CONFIG_CPU_R4300 is not set
+CONFIG_CPU_R4X00=y
+# CONFIG_CPU_TX49XX is not set
+# CONFIG_CPU_R5000 is not set
+# CONFIG_CPU_R5432 is not set
+# CONFIG_CPU_R6000 is not set
+# CONFIG_CPU_NEVADA is not set
+# CONFIG_CPU_R8000 is not set
+# CONFIG_CPU_R10000 is not set
+# CONFIG_CPU_RM7000 is not set
+# CONFIG_CPU_RM9000 is not set
+# CONFIG_CPU_SB1 is not set
+CONFIG_SYS_SUPPORTS_32BIT_KERNEL=y
+CONFIG_CPU_SUPPORTS_32BIT_KERNEL=y
+CONFIG_CPU_SUPPORTS_64BIT_KERNEL=y
+
+#
+# Kernel type
+#
+CONFIG_32BIT=y
+# CONFIG_64BIT is not set
+CONFIG_PAGE_SIZE_4KB=y
+# CONFIG_PAGE_SIZE_8KB is not set
+# CONFIG_PAGE_SIZE_16KB is not set
+# CONFIG_PAGE_SIZE_64KB is not set
+# CONFIG_MIPS_MT is not set
+# CONFIG_64BIT_PHYS_ADDR is not set
+# CONFIG_CPU_ADVANCED is not set
+CONFIG_CPU_HAS_LLSC=y
+CONFIG_CPU_HAS_LLDSCD=y
+CONFIG_CPU_HAS_SYNC=y
+CONFIG_ARCH_FLATMEM_ENABLE=y
+CONFIG_FLATMEM=y
+CONFIG_FLAT_NODE_MEM_MAP=y
+CONFIG_PREEMPT_NONE=y
+# CONFIG_PREEMPT_VOLUNTARY is not set
+# CONFIG_PREEMPT is not set
+
+#
+# Bus options (PCI, PCMCIA, EISA, ISA, TC)
+#
+CONFIG_ISA=y
+CONFIG_MMU=y
+
+#
+# PCCARD (PCMCIA/CardBus) support
+#
+# CONFIG_PCCARD is not set
+
+#
+# PCI Hotplug Support
+#
+
+#
+# Executable file formats
+#
+CONFIG_BINFMT_ELF=y
+# CONFIG_BINFMT_MISC is not set
+CONFIG_TRAD_SIGNALS=y
+
+#
+# Networking
+#
+CONFIG_NET=y
+
+#
+# Networking options
+#
+CONFIG_PACKET=y
+CONFIG_PACKET_MMAP=y
+CONFIG_UNIX=y
+# CONFIG_NET_KEY is not set
+CONFIG_INET=y
+CONFIG_IP_MULTICAST=y
+# CONFIG_IP_ADVANCED_ROUTER is not set
+CONFIG_IP_FIB_HASH=y
+CONFIG_IP_PNP=y
+CONFIG_IP_PNP_DHCP=y
+CONFIG_IP_PNP_BOOTP=y
+# CONFIG_IP_PNP_RARP is not set
+# CONFIG_NET_IPIP is not set
+# CONFIG_NET_IPGRE is not set
+# CONFIG_IP_MROUTE is not set
+# CONFIG_SYN_COOKIES is not set
+# CONFIG_INET_AH is not set
+# CONFIG_INET_ESP is not set
+# CONFIG_INET_IPCOMP is not set
+# CONFIG_INET_TUNNEL is not set
+CONFIG_IP_TCPDIAG=y
+# CONFIG_IP_TCPDIAG_IPV6 is not set
+# CONFIG_TCP_CONG_ADVANCED is not set
+CONFIG_TCP_CONG_BIC=y
+# CONFIG_IPV6 is not set
+# CONFIG_NETFILTER is not set
+# CONFIG_BRIDGE is not set
+# CONFIG_VLAN_8021Q is not set
+# CONFIG_DECNET is not set
+# CONFIG_LLC2 is not set
+# CONFIG_IPX is not set
+# CONFIG_ATALK is not set
+# CONFIG_NET_SCHED is not set
+# CONFIG_NET_CLS_ROUTE is not set
+
+#
+# Network testing
+#
+# CONFIG_HAMRADIO is not set
+# CONFIG_IRDA is not set
+# CONFIG_BT is not set
+
+#
+# Device Drivers
+#
+
+#
+# Generic Driver Options
+#
+CONFIG_STANDALONE=y
+# CONFIG_PREVENT_FIRMWARE_BUILD is not set
+# CONFIG_FW_LOADER is not set
+
+#
+# Memory Technology Devices (MTD)
+#
+# CONFIG_MTD is not set
+
+#
+# Parallel port support
+#
+# CONFIG_PARPORT is not set
+
+#
+# Plug and Play support
+#
+# CONFIG_PNP is not set
+
+#
+# Block devices
+#
+# CONFIG_BLK_DEV_FD is not set
+# CONFIG_BLK_DEV_COW_COMMON is not set
+# CONFIG_BLK_DEV_LOOP is not set
+# CONFIG_BLK_DEV_NBD is not set
+# CONFIG_BLK_DEV_RAM is not set
+CONFIG_BLK_DEV_RAM_COUNT=16
+CONFIG_INITRAMFS_SOURCE=""
+# CONFIG_CDROM_PKTCDVD is not set
+
+#
+# IO Schedulers
+#
+CONFIG_IOSCHED_NOOP=y
+# CONFIG_IOSCHED_AS is not set
+# CONFIG_IOSCHED_DEADLINE is not set
+# CONFIG_IOSCHED_CFQ is not set
+# CONFIG_ATA_OVER_ETH is not set
+
+#
+# ATA/ATAPI/MFM/RLL support
+#
+# CONFIG_IDE is not set
+
+#
+# SCSI device support
+#
+# CONFIG_SCSI is not set
+
+#
+# Old CD-ROM drivers (not SCSI, not IDE)
+#
+# CONFIG_CD_NO_IDESCSI is not set
+
+#
+# Multi-device support (RAID and LVM)
+#
+# CONFIG_MD is not set
+
+#
+# Fusion MPT device support
+#
+# CONFIG_FUSION is not set
+
+#
+# IEEE 1394 (FireWire) support
+#
+
+#
+# I2O device support
+#
+
+#
+# Network device support
+#
+CONFIG_NETDEVICES=y
+# CONFIG_DUMMY is not set
+# CONFIG_BONDING is not set
+# CONFIG_EQUALIZER is not set
+# CONFIG_TUN is not set
+
+#
+# ARCnet devices
+#
+# CONFIG_ARCNET is not set
+
+#
+# Ethernet (10 or 100Mbit)
+#
+CONFIG_NET_ETHERNET=y
+CONFIG_MII=y
+# CONFIG_NET_VENDOR_3COM is not set
+# CONFIG_NET_VENDOR_SMC is not set
+# CONFIG_NET_VENDOR_RACAL is not set
+# CONFIG_DEPCA is not set
+# CONFIG_HP100 is not set
+CONFIG_NET_ISA=y
+# CONFIG_E2100 is not set
+# CONFIG_EWRK3 is not set
+# CONFIG_EEXPRESS is not set
+# CONFIG_EEXPRESS_PRO is not set
+# CONFIG_HPLAN_PLUS is not set
+# CONFIG_HPLAN is not set
+# CONFIG_LP486E is not set
+# CONFIG_ETH16I is not set
+CONFIG_NE2000=y
+# CONFIG_NET_PCI is not set
+# CONFIG_NET_POCKET is not set
+
+#
+# Ethernet (1000 Mbit)
+#
+
+#
+# Ethernet (10000 Mbit)
+#
+
+#
+# Token Ring devices
+#
+# CONFIG_TR is not set
+
+#
+# Wireless LAN (non-hamradio)
+#
+# CONFIG_NET_RADIO is not set
+
+#
+# Wan interfaces
+#
+# CONFIG_WAN is not set
+# CONFIG_PPP is not set
+# CONFIG_SLIP is not set
+# CONFIG_NETPOLL is not set
+# CONFIG_NET_POLL_CONTROLLER is not set
+
+#
+# ISDN subsystem
+#
+# CONFIG_ISDN is not set
+
+#
+# Telephony Support
+#
+# CONFIG_PHONE is not set
+
+#
+# Input device support
+#
+CONFIG_INPUT=y
+
+#
+# Userland interfaces
+#
+# CONFIG_INPUT_MOUSEDEV is not set
+# CONFIG_INPUT_JOYDEV is not set
+# CONFIG_INPUT_TSDEV is not set
+# CONFIG_INPUT_EVDEV is not set
+# CONFIG_INPUT_EVBUG is not set
+
+#
+# Input Device Drivers
+#
+# CONFIG_INPUT_KEYBOARD is not set
+# CONFIG_INPUT_MOUSE is not set
+# CONFIG_INPUT_JOYSTICK is not set
+# CONFIG_INPUT_TOUCHSCREEN is not set
+# CONFIG_INPUT_MISC is not set
+
+#
+# Hardware I/O ports
+#
+# CONFIG_SERIO is not set
+# CONFIG_GAMEPORT is not set
+
+#
+# Character devices
+#
+CONFIG_VT=y
+CONFIG_VT_CONSOLE=y
+CONFIG_HW_CONSOLE=y
+# CONFIG_SERIAL_NONSTANDARD is not set
+
+#
+# Serial drivers
+#
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+CONFIG_SERIAL_8250_NR_UARTS=4
+# CONFIG_SERIAL_8250_EXTENDED is not set
+
+#
+# Non-8250 serial port support
+#
+CONFIG_SERIAL_CORE=y
+CONFIG_SERIAL_CORE_CONSOLE=y
+# CONFIG_UNIX98_PTYS is not set
+# CONFIG_LEGACY_PTYS is not set
+
+#
+# IPMI
+#
+# CONFIG_IPMI_HANDLER is not set
+
+#
+# Watchdog Cards
+#
+# CONFIG_WATCHDOG is not set
+# CONFIG_RTC is not set
+# CONFIG_GEN_RTC is not set
+# CONFIG_DTLK is not set
+# CONFIG_R3964 is not set
+
+#
+# Ftape, the floppy tape device driver
+#
+# CONFIG_RAW_DRIVER is not set
+
+#
+# TPM devices
+#
+
+#
+# I2C support
+#
+# CONFIG_I2C is not set
+# CONFIG_I2C_SENSOR is not set
+
+#
+# Dallas's 1-wire bus
+#
+# CONFIG_W1 is not set
+
+#
+# Hardware Monitoring support
+#
+# CONFIG_HWMON is not set
+
+#
+# Misc devices
+#
+
+#
+# Multimedia devices
+#
+# CONFIG_VIDEO_DEV is not set
+
+#
+# Digital Video Broadcasting Devices
+#
+# CONFIG_DVB is not set
+
+#
+# Graphics support
+#
+# CONFIG_FB is not set
+
+#
+# Console display driver support
+#
+CONFIG_VGA_CONSOLE=y
+# CONFIG_MDA_CONSOLE is not set
+CONFIG_DUMMY_CONSOLE=y
+
+#
+# Sound
+#
+# CONFIG_SOUND is not set
+
+#
+# USB support
+#
+# CONFIG_USB_ARCH_HAS_HCD is not set
+# CONFIG_USB_ARCH_HAS_OHCI is not set
+
+#
+# USB Gadget Support
+#
+# CONFIG_USB_GADGET is not set
+
+#
+# MMC/SD Card support
+#
+# CONFIG_MMC is not set
+
+#
+# InfiniBand support
+#
+# CONFIG_INFINIBAND is not set
+
+#
+# SN Devices
+#
+
+#
+# File systems
+#
+# CONFIG_EXT2_FS is not set
+# CONFIG_EXT3_FS is not set
+# CONFIG_JBD is not set
+# CONFIG_REISERFS_FS is not set
+# CONFIG_JFS_FS is not set
+# CONFIG_FS_POSIX_ACL is not set
+
+#
+# XFS support
+#
+# CONFIG_XFS_FS is not set
+# CONFIG_MINIX_FS is not set
+# CONFIG_ROMFS_FS is not set
+CONFIG_INOTIFY=y
+# CONFIG_QUOTA is not set
+# CONFIG_DNOTIFY is not set
+# CONFIG_AUTOFS_FS is not set
+# CONFIG_AUTOFS4_FS is not set
+
+#
+# CD-ROM/DVD Filesystems
+#
+# CONFIG_ISO9660_FS is not set
+# CONFIG_UDF_FS is not set
+
+#
+# DOS/FAT/NT Filesystems
+#
+# CONFIG_MSDOS_FS is not set
+# CONFIG_VFAT_FS is not set
+# CONFIG_NTFS_FS is not set
+
+#
+# Pseudo filesystems
+#
+# CONFIG_PROC_FS is not set
+# CONFIG_SYSFS is not set
+# CONFIG_TMPFS is not set
+# CONFIG_HUGETLB_PAGE is not set
+CONFIG_RAMFS=y
+
+#
+# Miscellaneous filesystems
+#
+# CONFIG_HFSPLUS_FS is not set
+# CONFIG_CRAMFS is not set
+# CONFIG_VXFS_FS is not set
+# CONFIG_HPFS_FS is not set
+# CONFIG_QNX4FS_FS is not set
+# CONFIG_SYSV_FS is not set
+# CONFIG_UFS_FS is not set
+
+#
+# Network File Systems
+#
+CONFIG_NFS_FS=y
+CONFIG_NFS_V3=y
+# CONFIG_NFS_V3_ACL is not set
+# CONFIG_NFSD is not set
+CONFIG_ROOT_NFS=y
+CONFIG_LOCKD=y
+CONFIG_LOCKD_V4=y
+CONFIG_NFS_COMMON=y
+CONFIG_SUNRPC=y
+# CONFIG_SMB_FS is not set
+# CONFIG_CIFS is not set
+# CONFIG_NCP_FS is not set
+# CONFIG_CODA_FS is not set
+
+#
+# Partition Types
+#
+# CONFIG_PARTITION_ADVANCED is not set
+CONFIG_MSDOS_PARTITION=y
+
+#
+# Native Language Support
+#
+# CONFIG_NLS is not set
+
+#
+# Kernel hacking
+#
+# CONFIG_PRINTK_TIME is not set
+# CONFIG_DEBUG_KERNEL is not set
+CONFIG_LOG_BUF_SHIFT=14
+CONFIG_CROSSCOMPILE=y
+CONFIG_CMDLINE="console=ttyS0 debug ip=172.20.0.2:172.20.0.1::255.255.0.0"
+
+#
+# Security options
+#
+# CONFIG_KEYS is not set
+# CONFIG_SECURITY is not set
+
+#
+# Cryptographic options
+#
+# CONFIG_CRYPTO is not set
+
+#
+# Hardware crypto devices
+#
+
+#
+# Library routines
+#
+# CONFIG_CRC_CCITT is not set
+CONFIG_CRC32=y
+# CONFIG_LIBCRC32C is not set
+CONFIG_GENERIC_HARDIRQS=y
+CONFIG_GENERIC_IRQ_PROBE=y

arch/mips/qemu/Makefile

+#
+# Makefile for Qemu specific kernel interface routines under Linux.
+#
+
+obj-y		= q-firmware.o q-int.o q-irq.o q-mem.o q-setup.o

arch/mips/qemu/q-firmware.c

+#include <linux/init.h>
+#include <asm/bootinfo.h>
+
+void __init prom_init(void)
+{
+	add_memory_region(0x0<<20, 0x10<<20, BOOT_MEM_RAM);
+}

arch/mips/qemu/q-int.S

+/*
+ * Qemu interrupt handler code.
+ *
+ * Copyright (C) 2005 by Ralf Baechle
+ */
+#include <asm/asm.h>
+#include <asm/regdef.h>
+#include <asm/stackframe.h>
+
+	.align	5
+	NESTED(qemu_handle_int, PT_SIZE, sp)
+	SAVE_ALL
+	CLI
+	move	a0, sp
+	PTR_LA	ra, ret_from_irq
+	j	do_qemu_int
+	END(qemu_handle_int)

arch/mips/qemu/q-irq.c

+#include <linux/init.h>
+#include <linux/linkage.h>
+
+#include <asm/i8259.h>
+#include <asm/mipsregs.h>
+#include <asm/qemu.h>
+#include <asm/system.h>
+#include <asm/time.h>
+
+extern asmlinkage void qemu_handle_int(void);
+
+asmlinkage void do_qemu_int(struct pt_regs *regs)
+{
+	unsigned int pending = read_c0_status() & read_c0_cause();
+
+	if (pending & 0x8000) {
+		ll_timer_interrupt(Q_COUNT_COMPARE_IRQ, regs);
+		return;
+	}
+	if (pending & 0x0400) {
+		int irq = i8259_irq();
+
+		if (likely(irq >= 0))
+			do_IRQ(irq, regs);
+
+		return;
+	}
+}
+
+void __init arch_init_irq(void)
+{
+	set_except_vector(0, qemu_handle_int);
+	mips_hpt_frequency = QEMU_C0_COUNTER_CLOCK;		/* 100MHz */
+
+	init_i8259_irqs();
+	set_c0_status(0x8400);
+}

arch/mips/qemu/q-mem.c

+#include <linux/init.h>
+
+unsigned long __init prom_free_prom_memory(void)
+{
+	return 0UL;
+}

arch/mips/qemu/q-setup.c

+#include <linux/init.h>
+#include <asm/io.h>
+#include <asm/time.h>
+
+#define QEMU_PORT_BASE 0xb4000000
+
+static void __init qemu_timer_setup(struct irqaction *irq)
+{
+	/* set the clock to 100 Hz */
+	outb_p(0x34,0x43);		/* binary, mode 2, LSB/MSB, ch 0 */
+	outb_p(LATCH & 0xff , 0x40);	/* LSB */
+	outb(LATCH >> 8 , 0x40);	/* MSB */
+	setup_irq(0, irq);
+}
+
+void __init plat_setup(void)
+{
+	set_io_port_base(QEMU_PORT_BASE);
+	board_timer_setup = qemu_timer_setup;
+}

include/asm-mips/mach-qemu/cpu-feature-overrides.h

+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2003 Ralf Baechle
+ */
+#ifndef __ASM_MACH_QEMU_CPU_FEATURE_OVERRIDES_H
+#define __ASM_MACH_QEMU_CPU_FEATURE_OVERRIDES_H
+
+/*
+ * QEMU only comes with a hazard-free MIPS32 processor, so things are easy.
+ */
+#define cpu_has_mips16		0
+#define cpu_has_divec		0
+#define cpu_has_cache_cdex_p	0
+#define cpu_has_prefetch	0
+#define cpu_has_mcheck		0
+#define cpu_has_ejtag		0
+
+#define cpu_has_llsc		1
+#define cpu_has_vtag_icache	0
+#define cpu_has_dc_aliases	(PAGE_SIZE < 0x4000)
+#define cpu_has_ic_fills_f_dc	0
+
+#define cpu_has_dsp		0
+
+#define cpu_has_nofpuex		0
+#define cpu_has_64bits		0
+
+#endif /* __ASM_MACH_QEMU_CPU_FEATURE_OVERRIDES_H */

include/asm-mips/mach-qemu/param.h

+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2005 by Ralf Baechle
+ */
+#ifndef __ASM_MACH_QEMU_PARAM_H
+#define __ASM_MACH_QEMU_PARAM_H
+
+#define HZ		100		/* Internal kernel timer frequency */
+
+#endif /* __ASM_MACH_QEMU_PARAM_H */

include/asm-mips/qemu.h

+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2005 by Ralf Baechle (ralf@linux-mips.org)
+ */
+#ifndef __ASM_QEMU_H
+#define __ASM_QEMU_H
+
+/*
+ * Interrupt numbers
+ */
+#define Q_PIC_IRQ_BASE		0
+#define Q_COUNT_COMPARE_IRQ	16
+
+/*
+ * Qemu clock rate.  Unlike on real MIPS this has no relation to the
+ * instruction issue rate, so the choosen value is pure fiction, just needs
+ * to match the value in Qemu itself.
+ */
+#define QEMU_C0_COUNTER_CLOCK	100000000
+
+#endif /* __ASM_QEMU_H */