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  1/*
  2 * This file is subject to the terms and conditions of the GNU General Public
  3 * License.  See the file "COPYING" in the main directory of this archive
  4 * for more details.
  5 *
  6 * Copyright (C) 2011 by Kevin Cernekee (cernekee@gmail.com)
  7 *
  8 * SMP support for BMIPS
  9 */
 10
 11#include <linux/init.h>
 12#include <linux/sched.h>
 13#include <linux/sched/hotplug.h>
 14#include <linux/sched/task_stack.h>
 15#include <linux/mm.h>
 16#include <linux/delay.h>
 17#include <linux/smp.h>
 18#include <linux/interrupt.h>
 19#include <linux/spinlock.h>
 20#include <linux/cpu.h>
 21#include <linux/cpumask.h>
 22#include <linux/reboot.h>
 23#include <linux/io.h>
 24#include <linux/compiler.h>
 25#include <linux/linkage.h>
 26#include <linux/bug.h>
 27#include <linux/kernel.h>
 28#include <linux/kexec.h>
 29#include <linux/irq.h>
 30
 31#include <asm/time.h>
 32#include <asm/processor.h>
 33#include <asm/bootinfo.h>
 34#include <asm/cacheflush.h>
 35#include <asm/tlbflush.h>
 36#include <asm/mipsregs.h>
 37#include <asm/bmips.h>
 38#include <asm/traps.h>
 39#include <asm/barrier.h>
 40#include <asm/cpu-features.h>
 41
 42static int __maybe_unused max_cpus = 1;
 43
 44/* these may be configured by the platform code */
 45int bmips_smp_enabled = 1;
 46int bmips_cpu_offset;
 47cpumask_t bmips_booted_mask;
 48unsigned long bmips_tp1_irqs = IE_IRQ1;
 49
 50#define RESET_FROM_KSEG0		0x80080800
 51#define RESET_FROM_KSEG1		0xa0080800
 52
 53static void bmips_set_reset_vec(int cpu, u32 val);
 54
 55#ifdef CONFIG_SMP
 56
 57/* initial $sp, $gp - used by arch/mips/kernel/bmips_vec.S */
 58unsigned long bmips_smp_boot_sp;
 59unsigned long bmips_smp_boot_gp;
 60
 61static void bmips43xx_send_ipi_single(int cpu, unsigned int action);
 62static void bmips5000_send_ipi_single(int cpu, unsigned int action);
 63static irqreturn_t bmips43xx_ipi_interrupt(int irq, void *dev_id);
 64static irqreturn_t bmips5000_ipi_interrupt(int irq, void *dev_id);
 65
 66/* SW interrupts 0,1 are used for interprocessor signaling */
 67#define IPI0_IRQ			(MIPS_CPU_IRQ_BASE + 0)
 68#define IPI1_IRQ			(MIPS_CPU_IRQ_BASE + 1)
 69
 70#define CPUNUM(cpu, shift)		(((cpu) + bmips_cpu_offset) << (shift))
 71#define ACTION_CLR_IPI(cpu, ipi)	(0x2000 | CPUNUM(cpu, 9) | ((ipi) << 8))
 72#define ACTION_SET_IPI(cpu, ipi)	(0x3000 | CPUNUM(cpu, 9) | ((ipi) << 8))
 73#define ACTION_BOOT_THREAD(cpu)		(0x08 | CPUNUM(cpu, 0))
 74
 75static void __init bmips_smp_setup(void)
 76{
 77	int i, cpu = 1, boot_cpu = 0;
 78	int cpu_hw_intr;
 79
 80	switch (current_cpu_type()) {
 81	case CPU_BMIPS4350:
 82	case CPU_BMIPS4380:
 83		/* arbitration priority */
 84		clear_c0_brcm_cmt_ctrl(0x30);
 85
 86		/* NBK and weak order flags */
 87		set_c0_brcm_config_0(0x30000);
 88
 89		/* Find out if we are running on TP0 or TP1 */
 90		boot_cpu = !!(read_c0_brcm_cmt_local() & (1 << 31));
 91
 92		/*
 93		 * MIPS interrupts 0,1 (SW INT 0,1) cross over to the other
 94		 * thread
 95		 * MIPS interrupt 2 (HW INT 0) is the CPU0 L1 controller output
 96		 * MIPS interrupt 3 (HW INT 1) is the CPU1 L1 controller output
 97		 */
 98		if (boot_cpu == 0)
 99			cpu_hw_intr = 0x02;
100		else
101			cpu_hw_intr = 0x1d;
102
103		change_c0_brcm_cmt_intr(0xf8018000,
104					(cpu_hw_intr << 27) | (0x03 << 15));
105
106		/* single core, 2 threads (2 pipelines) */
107		max_cpus = 2;
108
109		break;
110	case CPU_BMIPS5000:
111		/* enable raceless SW interrupts */
112		set_c0_brcm_config(0x03 << 22);
113
114		/* route HW interrupt 0 to CPU0, HW interrupt 1 to CPU1 */
115		change_c0_brcm_mode(0x1f << 27, 0x02 << 27);
116
117		/* N cores, 2 threads per core */
118		max_cpus = (((read_c0_brcm_config() >> 6) & 0x03) + 1) << 1;
119
120		/* clear any pending SW interrupts */
121		for (i = 0; i < max_cpus; i++) {
122			write_c0_brcm_action(ACTION_CLR_IPI(i, 0));
123			write_c0_brcm_action(ACTION_CLR_IPI(i, 1));
124		}
125
126		break;
127	default:
128		max_cpus = 1;
129	}
130
131	if (!bmips_smp_enabled)
132		max_cpus = 1;
133
134	/* this can be overridden by the BSP */
135	if (!board_ebase_setup)
136		board_ebase_setup = &bmips_ebase_setup;
137
138	if (max_cpus > 1) {
139		__cpu_number_map[boot_cpu] = 0;
140		__cpu_logical_map[0] = boot_cpu;
141
142		for (i = 0; i < max_cpus; i++) {
143			if (i != boot_cpu) {
144				__cpu_number_map[i] = cpu;
145				__cpu_logical_map[cpu] = i;
146				cpu++;
147			}
148			set_cpu_possible(i, 1);
149			set_cpu_present(i, 1);
150		}
151	} else {
152		__cpu_number_map[0] = boot_cpu;
153		__cpu_logical_map[0] = 0;
154		set_cpu_possible(0, 1);
155		set_cpu_present(0, 1);
156	}
157}
158
159/*
160 * IPI IRQ setup - runs on CPU0
161 */
162static void bmips_prepare_cpus(unsigned int max_cpus)
163{
164	irqreturn_t (*bmips_ipi_interrupt)(int irq, void *dev_id);
165
166	switch (current_cpu_type()) {
167	case CPU_BMIPS4350:
168	case CPU_BMIPS4380:
169		bmips_ipi_interrupt = bmips43xx_ipi_interrupt;
170		break;
171	case CPU_BMIPS5000:
172		bmips_ipi_interrupt = bmips5000_ipi_interrupt;
173		break;
174	default:
175		return;
176	}
177
178	if (request_irq(IPI0_IRQ, bmips_ipi_interrupt,
179			IRQF_PERCPU | IRQF_NO_SUSPEND, "smp_ipi0", NULL))
180		panic("Can't request IPI0 interrupt");
181	if (request_irq(IPI1_IRQ, bmips_ipi_interrupt,
182			IRQF_PERCPU | IRQF_NO_SUSPEND, "smp_ipi1", NULL))
183		panic("Can't request IPI1 interrupt");
184}
185
186/*
187 * Tell the hardware to boot CPUx - runs on CPU0
188 */
189static int bmips_boot_secondary(int cpu, struct task_struct *idle)
190{
191	bmips_smp_boot_sp = __KSTK_TOS(idle);
192	bmips_smp_boot_gp = (unsigned long)task_thread_info(idle);
193	mb();
194
195	/*
196	 * Initial boot sequence for secondary CPU:
197	 *   bmips_reset_nmi_vec @ a000_0000 ->
198	 *   bmips_smp_entry ->
199	 *   plat_wired_tlb_setup (cached function call; optional) ->
200	 *   start_secondary (cached jump)
201	 *
202	 * Warm restart sequence:
203	 *   play_dead WAIT loop ->
204	 *   bmips_smp_int_vec @ BMIPS_WARM_RESTART_VEC ->
205	 *   eret to play_dead ->
206	 *   bmips_secondary_reentry ->
207	 *   start_secondary
208	 */
209
210	pr_info("SMP: Booting CPU%d...\n", cpu);
211
212	if (cpumask_test_cpu(cpu, &bmips_booted_mask)) {
213		/* kseg1 might not exist if this CPU enabled XKS01 */
214		bmips_set_reset_vec(cpu, RESET_FROM_KSEG0);
215
216		switch (current_cpu_type()) {
217		case CPU_BMIPS4350:
218		case CPU_BMIPS4380:
219			bmips43xx_send_ipi_single(cpu, 0);
220			break;
221		case CPU_BMIPS5000:
222			bmips5000_send_ipi_single(cpu, 0);
223			break;
224		}
225	} else {
226		bmips_set_reset_vec(cpu, RESET_FROM_KSEG1);
227
228		switch (current_cpu_type()) {
229		case CPU_BMIPS4350:
230		case CPU_BMIPS4380:
231			/* Reset slave TP1 if booting from TP0 */
232			if (cpu_logical_map(cpu) == 1)
233				set_c0_brcm_cmt_ctrl(0x01);
234			break;
235		case CPU_BMIPS5000:
236			write_c0_brcm_action(ACTION_BOOT_THREAD(cpu));
237			break;
238		}
239		cpumask_set_cpu(cpu, &bmips_booted_mask);
240	}
241
242	return 0;
243}
244
245/*
246 * Early setup - runs on secondary CPU after cache probe
247 */
248static void bmips_init_secondary(void)
249{
250	bmips_cpu_setup();
251
252	switch (current_cpu_type()) {
253	case CPU_BMIPS4350:
254	case CPU_BMIPS4380:
255		clear_c0_cause(smp_processor_id() ? C_SW1 : C_SW0);
256		break;
257	case CPU_BMIPS5000:
258		write_c0_brcm_action(ACTION_CLR_IPI(smp_processor_id(), 0));
259		cpu_set_core(&current_cpu_data, (read_c0_brcm_config() >> 25) & 3);
260		break;
261	}
262}
263
264/*
265 * Late setup - runs on secondary CPU before entering the idle loop
266 */
267static void bmips_smp_finish(void)
268{
269	pr_info("SMP: CPU%d is running\n", smp_processor_id());
270
271	/* make sure there won't be a timer interrupt for a little while */
272	write_c0_compare(read_c0_count() + mips_hpt_frequency / HZ);
273
274	irq_enable_hazard();
275	set_c0_status(IE_SW0 | IE_SW1 | bmips_tp1_irqs | IE_IRQ5 | ST0_IE);
276	irq_enable_hazard();
277}
278
279/*
280 * BMIPS5000 raceless IPIs
281 *
282 * Each CPU has two inbound SW IRQs which are independent of all other CPUs.
283 * IPI0 is used for SMP_RESCHEDULE_YOURSELF
284 * IPI1 is used for SMP_CALL_FUNCTION
285 */
286
287static void bmips5000_send_ipi_single(int cpu, unsigned int action)
288{
289	write_c0_brcm_action(ACTION_SET_IPI(cpu, action == SMP_CALL_FUNCTION));
290}
291
292static irqreturn_t bmips5000_ipi_interrupt(int irq, void *dev_id)
293{
294	int action = irq - IPI0_IRQ;
295
296	write_c0_brcm_action(ACTION_CLR_IPI(smp_processor_id(), action));
297
298	if (action == 0)
299		scheduler_ipi();
300	else
301		generic_smp_call_function_interrupt();
302
303	return IRQ_HANDLED;
304}
305
306static void bmips5000_send_ipi_mask(const struct cpumask *mask,
307	unsigned int action)
308{
309	unsigned int i;
310
311	for_each_cpu(i, mask)
312		bmips5000_send_ipi_single(i, action);
313}
314
315/*
316 * BMIPS43xx racey IPIs
317 *
318 * We use one inbound SW IRQ for each CPU.
319 *
320 * A spinlock must be held in order to keep CPUx from accidentally clearing
321 * an incoming IPI when it writes CP0 CAUSE to raise an IPI on CPUy.  The
322 * same spinlock is used to protect the action masks.
323 */
324
325static DEFINE_SPINLOCK(ipi_lock);
326static DEFINE_PER_CPU(int, ipi_action_mask);
327
328static void bmips43xx_send_ipi_single(int cpu, unsigned int action)
329{
330	unsigned long flags;
331
332	spin_lock_irqsave(&ipi_lock, flags);
333	set_c0_cause(cpu ? C_SW1 : C_SW0);
334	per_cpu(ipi_action_mask, cpu) |= action;
335	irq_enable_hazard();
336	spin_unlock_irqrestore(&ipi_lock, flags);
337}
338
339static irqreturn_t bmips43xx_ipi_interrupt(int irq, void *dev_id)
340{
341	unsigned long flags;
342	int action, cpu = irq - IPI0_IRQ;
343
344	spin_lock_irqsave(&ipi_lock, flags);
345	action = __this_cpu_read(ipi_action_mask);
346	per_cpu(ipi_action_mask, cpu) = 0;
347	clear_c0_cause(cpu ? C_SW1 : C_SW0);
348	spin_unlock_irqrestore(&ipi_lock, flags);
349
350	if (action & SMP_RESCHEDULE_YOURSELF)
351		scheduler_ipi();
352	if (action & SMP_CALL_FUNCTION)
353		generic_smp_call_function_interrupt();
354
355	return IRQ_HANDLED;
356}
357
358static void bmips43xx_send_ipi_mask(const struct cpumask *mask,
359	unsigned int action)
360{
361	unsigned int i;
362
363	for_each_cpu(i, mask)
364		bmips43xx_send_ipi_single(i, action);
365}
366
367#ifdef CONFIG_HOTPLUG_CPU
368
369static int bmips_cpu_disable(void)
370{
371	unsigned int cpu = smp_processor_id();
372
373	pr_info("SMP: CPU%d is offline\n", cpu);
374
375	set_cpu_online(cpu, false);
376	calculate_cpu_foreign_map();
377	irq_migrate_all_off_this_cpu();
378	clear_c0_status(IE_IRQ5);
379
380	local_flush_tlb_all();
381	local_flush_icache_range(0, ~0);
382
383	return 0;
384}
385
386static void bmips_cpu_die(unsigned int cpu)
387{
388}
389
390void __ref play_dead(void)
391{
392	idle_task_exit();
393
394	/* flush data cache */
395	_dma_cache_wback_inv(0, ~0);
396
397	/*
398	 * Wakeup is on SW0 or SW1; disable everything else
399	 * Use BEV !IV (BMIPS_WARM_RESTART_VEC) to avoid the regular Linux
400	 * IRQ handlers; this clears ST0_IE and returns immediately.
401	 */
402	clear_c0_cause(CAUSEF_IV | C_SW0 | C_SW1);
403	change_c0_status(
404		IE_IRQ5 | bmips_tp1_irqs | IE_SW0 | IE_SW1 | ST0_IE | ST0_BEV,
405		IE_SW0 | IE_SW1 | ST0_IE | ST0_BEV);
406	irq_disable_hazard();
407
408	/*
409	 * wait for SW interrupt from bmips_boot_secondary(), then jump
410	 * back to start_secondary()
411	 */
412	__asm__ __volatile__(
413	"	wait\n"
414	"	j	bmips_secondary_reentry\n"
415	: : : "memory");
416}
417
418#endif /* CONFIG_HOTPLUG_CPU */
419
420const struct plat_smp_ops bmips43xx_smp_ops = {
421	.smp_setup		= bmips_smp_setup,
422	.prepare_cpus		= bmips_prepare_cpus,
423	.boot_secondary		= bmips_boot_secondary,
424	.smp_finish		= bmips_smp_finish,
425	.init_secondary		= bmips_init_secondary,
426	.send_ipi_single	= bmips43xx_send_ipi_single,
427	.send_ipi_mask		= bmips43xx_send_ipi_mask,
428#ifdef CONFIG_HOTPLUG_CPU
429	.cpu_disable		= bmips_cpu_disable,
430	.cpu_die		= bmips_cpu_die,
431#endif
432#ifdef CONFIG_KEXEC
433	.kexec_nonboot_cpu	= kexec_nonboot_cpu_jump,
434#endif
435};
436
437const struct plat_smp_ops bmips5000_smp_ops = {
438	.smp_setup		= bmips_smp_setup,
439	.prepare_cpus		= bmips_prepare_cpus,
440	.boot_secondary		= bmips_boot_secondary,
441	.smp_finish		= bmips_smp_finish,
442	.init_secondary		= bmips_init_secondary,
443	.send_ipi_single	= bmips5000_send_ipi_single,
444	.send_ipi_mask		= bmips5000_send_ipi_mask,
445#ifdef CONFIG_HOTPLUG_CPU
446	.cpu_disable		= bmips_cpu_disable,
447	.cpu_die		= bmips_cpu_die,
448#endif
449#ifdef CONFIG_KEXEC
450	.kexec_nonboot_cpu	= kexec_nonboot_cpu_jump,
451#endif
452};
453
454#endif /* CONFIG_SMP */
455
456/***********************************************************************
457 * BMIPS vector relocation
458 * This is primarily used for SMP boot, but it is applicable to some
459 * UP BMIPS systems as well.
460 ***********************************************************************/
461
462static void bmips_wr_vec(unsigned long dst, char *start, char *end)
463{
464	memcpy((void *)dst, start, end - start);
465	dma_cache_wback(dst, end - start);
466	local_flush_icache_range(dst, dst + (end - start));
467	instruction_hazard();
468}
469
470static inline void bmips_nmi_handler_setup(void)
471{
472	bmips_wr_vec(BMIPS_NMI_RESET_VEC, bmips_reset_nmi_vec,
473		bmips_reset_nmi_vec_end);
474	bmips_wr_vec(BMIPS_WARM_RESTART_VEC, bmips_smp_int_vec,
475		bmips_smp_int_vec_end);
476}
477
478struct reset_vec_info {
479	int cpu;
480	u32 val;
481};
482
483static void bmips_set_reset_vec_remote(void *vinfo)
484{
485	struct reset_vec_info *info = vinfo;
486	int shift = info->cpu & 0x01 ? 16 : 0;
487	u32 mask = ~(0xffff << shift), val = info->val >> 16;
488
489	preempt_disable();
490	if (smp_processor_id() > 0) {
491		smp_call_function_single(0, &bmips_set_reset_vec_remote,
492					 info, 1);
493	} else {
494		if (info->cpu & 0x02) {
495			/* BMIPS5200 "should" use mask/shift, but it's buggy */
496			bmips_write_zscm_reg(0xa0, (val << 16) | val);
497			bmips_read_zscm_reg(0xa0);
498		} else {
499			write_c0_brcm_bootvec((read_c0_brcm_bootvec() & mask) |
500					      (val << shift));
501		}
502	}
503	preempt_enable();
504}
505
506static void bmips_set_reset_vec(int cpu, u32 val)
507{
508	struct reset_vec_info info;
509
510	if (current_cpu_type() == CPU_BMIPS5000) {
511		/* this needs to run from CPU0 (which is always online) */
512		info.cpu = cpu;
513		info.val = val;
514		bmips_set_reset_vec_remote(&info);
515	} else {
516		void __iomem *cbr = BMIPS_GET_CBR();
517
518		if (cpu == 0)
519			__raw_writel(val, cbr + BMIPS_RELO_VECTOR_CONTROL_0);
520		else {
521			if (current_cpu_type() != CPU_BMIPS4380)
522				return;
523			__raw_writel(val, cbr + BMIPS_RELO_VECTOR_CONTROL_1);
524		}
525	}
526	__sync();
527	back_to_back_c0_hazard();
528}
529
530void bmips_ebase_setup(void)
531{
532	unsigned long new_ebase = ebase;
533
534	BUG_ON(ebase != CKSEG0);
535
536	switch (current_cpu_type()) {
537	case CPU_BMIPS4350:
538		/*
539		 * BMIPS4350 cannot relocate the normal vectors, but it
540		 * can relocate the BEV=1 vectors.  So CPU1 starts up at
541		 * the relocated BEV=1, IV=0 general exception vector @
542		 * 0xa000_0380.
543		 *
544		 * set_uncached_handler() is used here because:
545		 *  - CPU1 will run this from uncached space
546		 *  - None of the cacheflush functions are set up yet
547		 */
548		set_uncached_handler(BMIPS_WARM_RESTART_VEC - CKSEG0,
549			&bmips_smp_int_vec, 0x80);
550		__sync();
551		return;
552	case CPU_BMIPS3300:
553	case CPU_BMIPS4380:
554		/*
555		 * 0x8000_0000: reset/NMI (initially in kseg1)
556		 * 0x8000_0400: normal vectors
557		 */
558		new_ebase = 0x80000400;
559		bmips_set_reset_vec(0, RESET_FROM_KSEG0);
560		break;
561	case CPU_BMIPS5000:
562		/*
563		 * 0x8000_0000: reset/NMI (initially in kseg1)
564		 * 0x8000_1000: normal vectors
565		 */
566		new_ebase = 0x80001000;
567		bmips_set_reset_vec(0, RESET_FROM_KSEG0);
568		write_c0_ebase(new_ebase);
569		break;
570	default:
571		return;
572	}
573
574	board_nmi_handler_setup = &bmips_nmi_handler_setup;
575	ebase = new_ebase;
576}
577
578asmlinkage void __weak plat_wired_tlb_setup(void)
579{
580	/*
581	 * Called when starting/restarting a secondary CPU.
582	 * Kernel stacks and other important data might only be accessible
583	 * once the wired entries are present.
584	 */
585}
586
587void bmips_cpu_setup(void)
588{
589	void __iomem __maybe_unused *cbr = BMIPS_GET_CBR();
590	u32 __maybe_unused cfg;
591
592	switch (current_cpu_type()) {
593	case CPU_BMIPS3300:
594		/* Set BIU to async mode */
595		set_c0_brcm_bus_pll(BIT(22));
596		__sync();
597
598		/* put the BIU back in sync mode */
599		clear_c0_brcm_bus_pll(BIT(22));
600
601		/* clear BHTD to enable branch history table */
602		clear_c0_brcm_reset(BIT(16));
603
604		/* Flush and enable RAC */
605		cfg = __raw_readl(cbr + BMIPS_RAC_CONFIG);
606		__raw_writel(cfg | 0x100, cbr + BMIPS_RAC_CONFIG);
607		__raw_readl(cbr + BMIPS_RAC_CONFIG);
608
609		cfg = __raw_readl(cbr + BMIPS_RAC_CONFIG);
610		__raw_writel(cfg | 0xf, cbr + BMIPS_RAC_CONFIG);
611		__raw_readl(cbr + BMIPS_RAC_CONFIG);
612
613		cfg = __raw_readl(cbr + BMIPS_RAC_ADDRESS_RANGE);
614		__raw_writel(cfg | 0x0fff0000, cbr + BMIPS_RAC_ADDRESS_RANGE);
615		__raw_readl(cbr + BMIPS_RAC_ADDRESS_RANGE);
616		break;
617
618	case CPU_BMIPS4380:
619		/* CBG workaround for early BMIPS4380 CPUs */
620		switch (read_c0_prid()) {
621		case 0x2a040:
622		case 0x2a042:
623		case 0x2a044:
624		case 0x2a060:
625			cfg = __raw_readl(cbr + BMIPS_L2_CONFIG);
626			__raw_writel(cfg & ~0x07000000, cbr + BMIPS_L2_CONFIG);
627			__raw_readl(cbr + BMIPS_L2_CONFIG);
628		}
629
630		/* clear BHTD to enable branch history table */
631		clear_c0_brcm_config_0(BIT(21));
632
633		/* XI/ROTR enable */
634		set_c0_brcm_config_0(BIT(23));
635		set_c0_brcm_cmt_ctrl(BIT(15));
636		break;
637
638	case CPU_BMIPS5000:
639		/* enable RDHWR, BRDHWR */
640		set_c0_brcm_config(BIT(17) | BIT(21));
641
642		/* Disable JTB */
643		__asm__ __volatile__(
644		"	.set	noreorder\n"
645		"	li	$8, 0x5a455048\n"
646		"	.word	0x4088b00f\n"	/* mtc0	t0, $22, 15 */
647		"	.word	0x4008b008\n"	/* mfc0	t0, $22, 8 */
648		"	li	$9, 0x00008000\n"
649		"	or	$8, $8, $9\n"
650		"	.word	0x4088b008\n"	/* mtc0	t0, $22, 8 */
651		"	sync\n"
652		"	li	$8, 0x0\n"
653		"	.word	0x4088b00f\n"	/* mtc0	t0, $22, 15 */
654		"	.set	reorder\n"
655		: : : "$8", "$9");
656
657		/* XI enable */
658		set_c0_brcm_config(BIT(27));
659
660		/* enable MIPS32R2 ROR instruction for XI TLB handlers */
661		__asm__ __volatile__(
662		"	li	$8, 0x5a455048\n"
663		"	.word	0x4088b00f\n"	/* mtc0 $8, $22, 15 */
664		"	nop; nop; nop\n"
665		"	.word	0x4008b008\n"	/* mfc0 $8, $22, 8 */
666		"	lui	$9, 0x0100\n"
667		"	or	$8, $9\n"
668		"	.word	0x4088b008\n"	/* mtc0 $8, $22, 8 */
669		: : : "$8", "$9");
670		break;
671	}
672}