Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 662 insertions, 0 deletions

diff --git a/arch/mips/kernel/smp-bmips.c b/arch/mips/kernel/smp-bmips.c
new file mode 100644
index 000000000..d16e6654a
--- /dev/null
+++ b/arch/mips/kernel/smp-bmips.c
@@ -0,0 +1,662 @@
+/*
+ * 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) 2011 by Kevin Cernekee (cernekee@gmail.com)
+ *
+ * SMP support for BMIPS
+ */
+
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/sched/hotplug.h>
+#include <linux/sched/task_stack.h>
+#include <linux/mm.h>
+#include <linux/delay.h>
+#include <linux/smp.h>
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/reboot.h>
+#include <linux/io.h>
+#include <linux/compiler.h>
+#include <linux/linkage.h>
+#include <linux/bug.h>
+#include <linux/kernel.h>
+
+#include <asm/time.h>
+#include <asm/pgtable.h>
+#include <asm/processor.h>
+#include <asm/bootinfo.h>
+#include <asm/pmon.h>
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+#include <asm/mipsregs.h>
+#include <asm/bmips.h>
+#include <asm/traps.h>
+#include <asm/barrier.h>
+#include <asm/cpu-features.h>
+
+static int __maybe_unused max_cpus = 1;
+
+/* these may be configured by the platform code */
+int bmips_smp_enabled = 1;
+int bmips_cpu_offset;
+cpumask_t bmips_booted_mask;
+unsigned long bmips_tp1_irqs = IE_IRQ1;
+
+#define RESET_FROM_KSEG0		0x80080800
+#define RESET_FROM_KSEG1		0xa0080800
+
+static void bmips_set_reset_vec(int cpu, u32 val);
+
+#ifdef CONFIG_SMP
+
+/* initial $sp, $gp - used by arch/mips/kernel/bmips_vec.S */
+unsigned long bmips_smp_boot_sp;
+unsigned long bmips_smp_boot_gp;
+
+static void bmips43xx_send_ipi_single(int cpu, unsigned int action);
+static void bmips5000_send_ipi_single(int cpu, unsigned int action);
+static irqreturn_t bmips43xx_ipi_interrupt(int irq, void *dev_id);
+static irqreturn_t bmips5000_ipi_interrupt(int irq, void *dev_id);
+
+/* SW interrupts 0,1 are used for interprocessor signaling */
+#define IPI0_IRQ			(MIPS_CPU_IRQ_BASE + 0)
+#define IPI1_IRQ			(MIPS_CPU_IRQ_BASE + 1)
+
+#define CPUNUM(cpu, shift)		(((cpu) + bmips_cpu_offset) << (shift))
+#define ACTION_CLR_IPI(cpu, ipi)	(0x2000 | CPUNUM(cpu, 9) | ((ipi) << 8))
+#define ACTION_SET_IPI(cpu, ipi)	(0x3000 | CPUNUM(cpu, 9) | ((ipi) << 8))
+#define ACTION_BOOT_THREAD(cpu)		(0x08 | CPUNUM(cpu, 0))
+
+static void __init bmips_smp_setup(void)
+{
+	int i, cpu = 1, boot_cpu = 0;
+	int cpu_hw_intr;
+
+	switch (current_cpu_type()) {
+	case CPU_BMIPS4350:
+	case CPU_BMIPS4380:
+		/* arbitration priority */
+		clear_c0_brcm_cmt_ctrl(0x30);
+
+		/* NBK and weak order flags */
+		set_c0_brcm_config_0(0x30000);
+
+		/* Find out if we are running on TP0 or TP1 */
+		boot_cpu = !!(read_c0_brcm_cmt_local() & (1 << 31));
+
+		/*
+		 * MIPS interrupts 0,1 (SW INT 0,1) cross over to the other
+		 * thread
+		 * MIPS interrupt 2 (HW INT 0) is the CPU0 L1 controller output
+		 * MIPS interrupt 3 (HW INT 1) is the CPU1 L1 controller output
+		 */
+		if (boot_cpu == 0)
+			cpu_hw_intr = 0x02;
+		else
+			cpu_hw_intr = 0x1d;
+
+		change_c0_brcm_cmt_intr(0xf8018000,
+					(cpu_hw_intr << 27) | (0x03 << 15));
+
+		/* single core, 2 threads (2 pipelines) */
+		max_cpus = 2;
+
+		break;
+	case CPU_BMIPS5000:
+		/* enable raceless SW interrupts */
+		set_c0_brcm_config(0x03 << 22);
+
+		/* route HW interrupt 0 to CPU0, HW interrupt 1 to CPU1 */
+		change_c0_brcm_mode(0x1f << 27, 0x02 << 27);
+
+		/* N cores, 2 threads per core */
+		max_cpus = (((read_c0_brcm_config() >> 6) & 0x03) + 1) << 1;
+
+		/* clear any pending SW interrupts */
+		for (i = 0; i < max_cpus; i++) {
+			write_c0_brcm_action(ACTION_CLR_IPI(i, 0));
+			write_c0_brcm_action(ACTION_CLR_IPI(i, 1));
+		}
+
+		break;
+	default:
+		max_cpus = 1;
+	}
+
+	if (!bmips_smp_enabled)
+		max_cpus = 1;
+
+	/* this can be overridden by the BSP */
+	if (!board_ebase_setup)
+		board_ebase_setup = &bmips_ebase_setup;
+
+	__cpu_number_map[boot_cpu] = 0;
+	__cpu_logical_map[0] = boot_cpu;
+
+	for (i = 0; i < max_cpus; i++) {
+		if (i != boot_cpu) {
+			__cpu_number_map[i] = cpu;
+			__cpu_logical_map[cpu] = i;
+			cpu++;
+		}
+		set_cpu_possible(i, 1);
+		set_cpu_present(i, 1);
+	}
+}
+
+/*
+ * IPI IRQ setup - runs on CPU0
+ */
+static void bmips_prepare_cpus(unsigned int max_cpus)
+{
+	irqreturn_t (*bmips_ipi_interrupt)(int irq, void *dev_id);
+
+	switch (current_cpu_type()) {
+	case CPU_BMIPS4350:
+	case CPU_BMIPS4380:
+		bmips_ipi_interrupt = bmips43xx_ipi_interrupt;
+		break;
+	case CPU_BMIPS5000:
+		bmips_ipi_interrupt = bmips5000_ipi_interrupt;
+		break;
+	default:
+		return;
+	}
+
+	if (request_irq(IPI0_IRQ, bmips_ipi_interrupt,
+			IRQF_PERCPU | IRQF_NO_SUSPEND, "smp_ipi0", NULL))
+		panic("Can't request IPI0 interrupt");
+	if (request_irq(IPI1_IRQ, bmips_ipi_interrupt,
+			IRQF_PERCPU | IRQF_NO_SUSPEND, "smp_ipi1", NULL))
+		panic("Can't request IPI1 interrupt");
+}
+
+/*
+ * Tell the hardware to boot CPUx - runs on CPU0
+ */
+static int bmips_boot_secondary(int cpu, struct task_struct *idle)
+{
+	bmips_smp_boot_sp = __KSTK_TOS(idle);
+	bmips_smp_boot_gp = (unsigned long)task_thread_info(idle);
+	mb();
+
+	/*
+	 * Initial boot sequence for secondary CPU:
+	 *   bmips_reset_nmi_vec @ a000_0000 ->
+	 *   bmips_smp_entry ->
+	 *   plat_wired_tlb_setup (cached function call; optional) ->
+	 *   start_secondary (cached jump)
+	 *
+	 * Warm restart sequence:
+	 *   play_dead WAIT loop ->
+	 *   bmips_smp_int_vec @ BMIPS_WARM_RESTART_VEC ->
+	 *   eret to play_dead ->
+	 *   bmips_secondary_reentry ->
+	 *   start_secondary
+	 */
+
+	pr_info("SMP: Booting CPU%d...\n", cpu);
+
+	if (cpumask_test_cpu(cpu, &bmips_booted_mask)) {
+		/* kseg1 might not exist if this CPU enabled XKS01 */
+		bmips_set_reset_vec(cpu, RESET_FROM_KSEG0);
+
+		switch (current_cpu_type()) {
+		case CPU_BMIPS4350:
+		case CPU_BMIPS4380:
+			bmips43xx_send_ipi_single(cpu, 0);
+			break;
+		case CPU_BMIPS5000:
+			bmips5000_send_ipi_single(cpu, 0);
+			break;
+		}
+	} else {
+		bmips_set_reset_vec(cpu, RESET_FROM_KSEG1);
+
+		switch (current_cpu_type()) {
+		case CPU_BMIPS4350:
+		case CPU_BMIPS4380:
+			/* Reset slave TP1 if booting from TP0 */
+			if (cpu_logical_map(cpu) == 1)
+				set_c0_brcm_cmt_ctrl(0x01);
+			break;
+		case CPU_BMIPS5000:
+			write_c0_brcm_action(ACTION_BOOT_THREAD(cpu));
+			break;
+		}
+		cpumask_set_cpu(cpu, &bmips_booted_mask);
+	}
+
+	return 0;
+}
+
+/*
+ * Early setup - runs on secondary CPU after cache probe
+ */
+static void bmips_init_secondary(void)
+{
+	bmips_cpu_setup();
+
+	switch (current_cpu_type()) {
+	case CPU_BMIPS4350:
+	case CPU_BMIPS4380:
+		clear_c0_cause(smp_processor_id() ? C_SW1 : C_SW0);
+		break;
+	case CPU_BMIPS5000:
+		write_c0_brcm_action(ACTION_CLR_IPI(smp_processor_id(), 0));
+		cpu_set_core(&current_cpu_data, (read_c0_brcm_config() >> 25) & 3);
+		break;
+	}
+}
+
+/*
+ * Late setup - runs on secondary CPU before entering the idle loop
+ */
+static void bmips_smp_finish(void)
+{
+	pr_info("SMP: CPU%d is running\n", smp_processor_id());
+
+	/* make sure there won't be a timer interrupt for a little while */
+	write_c0_compare(read_c0_count() + mips_hpt_frequency / HZ);
+
+	irq_enable_hazard();
+	set_c0_status(IE_SW0 | IE_SW1 | bmips_tp1_irqs | IE_IRQ5 | ST0_IE);
+	irq_enable_hazard();
+}
+
+/*
+ * BMIPS5000 raceless IPIs
+ *
+ * Each CPU has two inbound SW IRQs which are independent of all other CPUs.
+ * IPI0 is used for SMP_RESCHEDULE_YOURSELF
+ * IPI1 is used for SMP_CALL_FUNCTION
+ */
+
+static void bmips5000_send_ipi_single(int cpu, unsigned int action)
+{
+	write_c0_brcm_action(ACTION_SET_IPI(cpu, action == SMP_CALL_FUNCTION));
+}
+
+static irqreturn_t bmips5000_ipi_interrupt(int irq, void *dev_id)
+{
+	int action = irq - IPI0_IRQ;
+
+	write_c0_brcm_action(ACTION_CLR_IPI(smp_processor_id(), action));
+
+	if (action == 0)
+		scheduler_ipi();
+	else
+		generic_smp_call_function_interrupt();
+
+	return IRQ_HANDLED;
+}
+
+static void bmips5000_send_ipi_mask(const struct cpumask *mask,
+	unsigned int action)
+{
+	unsigned int i;
+
+	for_each_cpu(i, mask)
+		bmips5000_send_ipi_single(i, action);
+}
+
+/*
+ * BMIPS43xx racey IPIs
+ *
+ * We use one inbound SW IRQ for each CPU.
+ *
+ * A spinlock must be held in order to keep CPUx from accidentally clearing
+ * an incoming IPI when it writes CP0 CAUSE to raise an IPI on CPUy.  The
+ * same spinlock is used to protect the action masks.
+ */
+
+static DEFINE_SPINLOCK(ipi_lock);
+static DEFINE_PER_CPU(int, ipi_action_mask);
+
+static void bmips43xx_send_ipi_single(int cpu, unsigned int action)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&ipi_lock, flags);
+	set_c0_cause(cpu ? C_SW1 : C_SW0);
+	per_cpu(ipi_action_mask, cpu) |= action;
+	irq_enable_hazard();
+	spin_unlock_irqrestore(&ipi_lock, flags);
+}
+
+static irqreturn_t bmips43xx_ipi_interrupt(int irq, void *dev_id)
+{
+	unsigned long flags;
+	int action, cpu = irq - IPI0_IRQ;
+
+	spin_lock_irqsave(&ipi_lock, flags);
+	action = __this_cpu_read(ipi_action_mask);
+	per_cpu(ipi_action_mask, cpu) = 0;
+	clear_c0_cause(cpu ? C_SW1 : C_SW0);
+	spin_unlock_irqrestore(&ipi_lock, flags);
+
+	if (action & SMP_RESCHEDULE_YOURSELF)
+		scheduler_ipi();
+	if (action & SMP_CALL_FUNCTION)
+		generic_smp_call_function_interrupt();
+
+	return IRQ_HANDLED;
+}
+
+static void bmips43xx_send_ipi_mask(const struct cpumask *mask,
+	unsigned int action)
+{
+	unsigned int i;
+
+	for_each_cpu(i, mask)
+		bmips43xx_send_ipi_single(i, action);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+static int bmips_cpu_disable(void)
+{
+	unsigned int cpu = smp_processor_id();
+
+	if (cpu == 0)
+		return -EBUSY;
+
+	pr_info("SMP: CPU%d is offline\n", cpu);
+
+	set_cpu_online(cpu, false);
+	calculate_cpu_foreign_map();
+	irq_cpu_offline();
+	clear_c0_status(IE_IRQ5);
+
+	local_flush_tlb_all();
+	local_flush_icache_range(0, ~0);
+
+	return 0;
+}
+
+static void bmips_cpu_die(unsigned int cpu)
+{
+}
+
+void __ref play_dead(void)
+{
+	idle_task_exit();
+
+	/* flush data cache */
+	_dma_cache_wback_inv(0, ~0);
+
+	/*
+	 * Wakeup is on SW0 or SW1; disable everything else
+	 * Use BEV !IV (BMIPS_WARM_RESTART_VEC) to avoid the regular Linux
+	 * IRQ handlers; this clears ST0_IE and returns immediately.
+	 */
+	clear_c0_cause(CAUSEF_IV | C_SW0 | C_SW1);
+	change_c0_status(
+		IE_IRQ5 | bmips_tp1_irqs | IE_SW0 | IE_SW1 | ST0_IE | ST0_BEV,
+		IE_SW0 | IE_SW1 | ST0_IE | ST0_BEV);
+	irq_disable_hazard();
+
+	/*
+	 * wait for SW interrupt from bmips_boot_secondary(), then jump
+	 * back to start_secondary()
+	 */
+	__asm__ __volatile__(
+	"	wait\n"
+	"	j	bmips_secondary_reentry\n"
+	: : : "memory");
+}
+
+#endif /* CONFIG_HOTPLUG_CPU */
+
+const struct plat_smp_ops bmips43xx_smp_ops = {
+	.smp_setup		= bmips_smp_setup,
+	.prepare_cpus		= bmips_prepare_cpus,
+	.boot_secondary		= bmips_boot_secondary,
+	.smp_finish		= bmips_smp_finish,
+	.init_secondary		= bmips_init_secondary,
+	.send_ipi_single	= bmips43xx_send_ipi_single,
+	.send_ipi_mask		= bmips43xx_send_ipi_mask,
+#ifdef CONFIG_HOTPLUG_CPU
+	.cpu_disable		= bmips_cpu_disable,
+	.cpu_die		= bmips_cpu_die,
+#endif
+};
+
+const struct plat_smp_ops bmips5000_smp_ops = {
+	.smp_setup		= bmips_smp_setup,
+	.prepare_cpus		= bmips_prepare_cpus,
+	.boot_secondary		= bmips_boot_secondary,
+	.smp_finish		= bmips_smp_finish,
+	.init_secondary		= bmips_init_secondary,
+	.send_ipi_single	= bmips5000_send_ipi_single,
+	.send_ipi_mask		= bmips5000_send_ipi_mask,
+#ifdef CONFIG_HOTPLUG_CPU
+	.cpu_disable		= bmips_cpu_disable,
+	.cpu_die		= bmips_cpu_die,
+#endif
+};
+
+#endif /* CONFIG_SMP */
+
+/***********************************************************************
+ * BMIPS vector relocation
+ * This is primarily used for SMP boot, but it is applicable to some
+ * UP BMIPS systems as well.
+ ***********************************************************************/
+
+static void bmips_wr_vec(unsigned long dst, char *start, char *end)
+{
+	memcpy((void *)dst, start, end - start);
+	dma_cache_wback(dst, end - start);
+	local_flush_icache_range(dst, dst + (end - start));
+	instruction_hazard();
+}
+
+static inline void bmips_nmi_handler_setup(void)
+{
+	bmips_wr_vec(BMIPS_NMI_RESET_VEC, bmips_reset_nmi_vec,
+		bmips_reset_nmi_vec_end);
+	bmips_wr_vec(BMIPS_WARM_RESTART_VEC, bmips_smp_int_vec,
+		bmips_smp_int_vec_end);
+}
+
+struct reset_vec_info {
+	int cpu;
+	u32 val;
+};
+
+static void bmips_set_reset_vec_remote(void *vinfo)
+{
+	struct reset_vec_info *info = vinfo;
+	int shift = info->cpu & 0x01 ? 16 : 0;
+	u32 mask = ~(0xffff << shift), val = info->val >> 16;
+
+	preempt_disable();
+	if (smp_processor_id() > 0) {
+		smp_call_function_single(0, &bmips_set_reset_vec_remote,
+					 info, 1);
+	} else {
+		if (info->cpu & 0x02) {
+			/* BMIPS5200 "should" use mask/shift, but it's buggy */
+			bmips_write_zscm_reg(0xa0, (val << 16) | val);
+			bmips_read_zscm_reg(0xa0);
+		} else {
+			write_c0_brcm_bootvec((read_c0_brcm_bootvec() & mask) |
+					      (val << shift));
+		}
+	}
+	preempt_enable();
+}
+
+static void bmips_set_reset_vec(int cpu, u32 val)
+{
+	struct reset_vec_info info;
+
+	if (current_cpu_type() == CPU_BMIPS5000) {
+		/* this needs to run from CPU0 (which is always online) */
+		info.cpu = cpu;
+		info.val = val;
+		bmips_set_reset_vec_remote(&info);
+	} else {
+		void __iomem *cbr = BMIPS_GET_CBR();
+
+		if (cpu == 0)
+			__raw_writel(val, cbr + BMIPS_RELO_VECTOR_CONTROL_0);
+		else {
+			if (current_cpu_type() != CPU_BMIPS4380)
+				return;
+			__raw_writel(val, cbr + BMIPS_RELO_VECTOR_CONTROL_1);
+		}
+	}
+	__sync();
+	back_to_back_c0_hazard();
+}
+
+void bmips_ebase_setup(void)
+{
+	unsigned long new_ebase = ebase;
+
+	BUG_ON(ebase != CKSEG0);
+
+	switch (current_cpu_type()) {
+	case CPU_BMIPS4350:
+		/*
+		 * BMIPS4350 cannot relocate the normal vectors, but it
+		 * can relocate the BEV=1 vectors.  So CPU1 starts up at
+		 * the relocated BEV=1, IV=0 general exception vector @
+		 * 0xa000_0380.
+		 *
+		 * set_uncached_handler() is used here because:
+		 *  - CPU1 will run this from uncached space
+		 *  - None of the cacheflush functions are set up yet
+		 */
+		set_uncached_handler(BMIPS_WARM_RESTART_VEC - CKSEG0,
+			&bmips_smp_int_vec, 0x80);
+		__sync();
+		return;
+	case CPU_BMIPS3300:
+	case CPU_BMIPS4380:
+		/*
+		 * 0x8000_0000: reset/NMI (initially in kseg1)
+		 * 0x8000_0400: normal vectors
+		 */
+		new_ebase = 0x80000400;
+		bmips_set_reset_vec(0, RESET_FROM_KSEG0);
+		break;
+	case CPU_BMIPS5000:
+		/*
+		 * 0x8000_0000: reset/NMI (initially in kseg1)
+		 * 0x8000_1000: normal vectors
+		 */
+		new_ebase = 0x80001000;
+		bmips_set_reset_vec(0, RESET_FROM_KSEG0);
+		write_c0_ebase(new_ebase);
+		break;
+	default:
+		return;
+	}
+
+	board_nmi_handler_setup = &bmips_nmi_handler_setup;
+	ebase = new_ebase;
+}
+
+asmlinkage void __weak plat_wired_tlb_setup(void)
+{
+	/*
+	 * Called when starting/restarting a secondary CPU.
+	 * Kernel stacks and other important data might only be accessible
+	 * once the wired entries are present.
+	 */
+}
+
+void bmips_cpu_setup(void)
+{
+	void __iomem __maybe_unused *cbr = BMIPS_GET_CBR();
+	u32 __maybe_unused cfg;
+
+	switch (current_cpu_type()) {
+	case CPU_BMIPS3300:
+		/* Set BIU to async mode */
+		set_c0_brcm_bus_pll(BIT(22));
+		__sync();
+
+		/* put the BIU back in sync mode */
+		clear_c0_brcm_bus_pll(BIT(22));
+
+		/* clear BHTD to enable branch history table */
+		clear_c0_brcm_reset(BIT(16));
+
+		/* Flush and enable RAC */
+		cfg = __raw_readl(cbr + BMIPS_RAC_CONFIG);
+		__raw_writel(cfg | 0x100, cbr + BMIPS_RAC_CONFIG);
+		__raw_readl(cbr + BMIPS_RAC_CONFIG);
+
+		cfg = __raw_readl(cbr + BMIPS_RAC_CONFIG);
+		__raw_writel(cfg | 0xf, cbr + BMIPS_RAC_CONFIG);
+		__raw_readl(cbr + BMIPS_RAC_CONFIG);
+
+		cfg = __raw_readl(cbr + BMIPS_RAC_ADDRESS_RANGE);
+		__raw_writel(cfg | 0x0fff0000, cbr + BMIPS_RAC_ADDRESS_RANGE);
+		__raw_readl(cbr + BMIPS_RAC_ADDRESS_RANGE);
+		break;
+
+	case CPU_BMIPS4380:
+		/* CBG workaround for early BMIPS4380 CPUs */
+		switch (read_c0_prid()) {
+		case 0x2a040:
+		case 0x2a042:
+		case 0x2a044:
+		case 0x2a060:
+			cfg = __raw_readl(cbr + BMIPS_L2_CONFIG);
+			__raw_writel(cfg & ~0x07000000, cbr + BMIPS_L2_CONFIG);
+			__raw_readl(cbr + BMIPS_L2_CONFIG);
+		}
+
+		/* clear BHTD to enable branch history table */
+		clear_c0_brcm_config_0(BIT(21));
+
+		/* XI/ROTR enable */
+		set_c0_brcm_config_0(BIT(23));
+		set_c0_brcm_cmt_ctrl(BIT(15));
+		break;
+
+	case CPU_BMIPS5000:
+		/* enable RDHWR, BRDHWR */
+		set_c0_brcm_config(BIT(17) | BIT(21));
+
+		/* Disable JTB */
+		__asm__ __volatile__(
+		"	.set	noreorder\n"
+		"	li	$8, 0x5a455048\n"
+		"	.word	0x4088b00f\n"	/* mtc0	t0, $22, 15 */
+		"	.word	0x4008b008\n"	/* mfc0	t0, $22, 8 */
+		"	li	$9, 0x00008000\n"
+		"	or	$8, $8, $9\n"
+		"	.word	0x4088b008\n"	/* mtc0	t0, $22, 8 */
+		"	sync\n"
+		"	li	$8, 0x0\n"
+		"	.word	0x4088b00f\n"	/* mtc0	t0, $22, 15 */
+		"	.set	reorder\n"
+		: : : "$8", "$9");
+
+		/* XI enable */
+		set_c0_brcm_config(BIT(27));
+
+		/* enable MIPS32R2 ROR instruction for XI TLB handlers */
+		__asm__ __volatile__(
+		"	li	$8, 0x5a455048\n"
+		"	.word	0x4088b00f\n"	/* mtc0 $8, $22, 15 */
+		"	nop; nop; nop\n"
+		"	.word	0x4008b008\n"	/* mfc0 $8, $22, 8 */
+		"	lui	$9, 0x0100\n"
+		"	or	$8, $9\n"
+		"	.word	0x4088b008\n"	/* mtc0 $8, $22, 8 */
+		: : : "$8", "$9");
+		break;
+	}
+}