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1 /*
2  *  linux/arch/arm/mach-realview/hotplug.c
3  *
4  *  Copyright (C) 2002 ARM Ltd.
5  *  All Rights Reserved
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License version 2 as
9  * published by the Free Software Foundation.
10  */
11 #include <linux/kernel.h>
12 #include <linux/errno.h>
13 #include <linux/smp.h>
14 
15 #include <asm/smp_plat.h>
16 #include <asm/cp15.h>
17 
cpu_enter_lowpower(void)18 static inline void cpu_enter_lowpower(void)
19 {
20 	unsigned int v;
21 
22 	asm volatile(
23 		"mcr	p15, 0, %1, c7, c5, 0\n"
24 	"	mcr	p15, 0, %1, c7, c10, 4\n"
25 	/*
26 	 * Turn off coherency
27 	 */
28 	"	mrc	p15, 0, %0, c1, c0, 1\n"
29 	"	bic	%0, %0, %3\n"
30 	"	mcr	p15, 0, %0, c1, c0, 1\n"
31 	"	mrc	p15, 0, %0, c1, c0, 0\n"
32 	"	bic	%0, %0, %2\n"
33 	"	mcr	p15, 0, %0, c1, c0, 0\n"
34 	  : "=&r" (v)
35 	  : "r" (0), "Ir" (CR_C), "Ir" (0x40)
36 	  : "cc");
37 }
38 
cpu_leave_lowpower(void)39 static inline void cpu_leave_lowpower(void)
40 {
41 	unsigned int v;
42 
43 	asm volatile(
44 		"mrc	p15, 0, %0, c1, c0, 0\n"
45 	"	orr	%0, %0, %1\n"
46 	"	mcr	p15, 0, %0, c1, c0, 0\n"
47 	"	mrc	p15, 0, %0, c1, c0, 1\n"
48 	"	orr	%0, %0, %2\n"
49 	"	mcr	p15, 0, %0, c1, c0, 1\n"
50 	  : "=&r" (v)
51 	  : "Ir" (CR_C), "Ir" (0x40)
52 	  : "cc");
53 }
54 
platform_do_lowpower(unsigned int cpu,int * spurious)55 static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
56 {
57 	/*
58 	 * there is no power-control hardware on this platform, so all
59 	 * we can do is put the core into WFI; this is safe as the calling
60 	 * code will have already disabled interrupts
61 	 */
62 	for (;;) {
63 		wfi();
64 
65 		if (pen_release == cpu_logical_map(cpu)) {
66 			/*
67 			 * OK, proper wakeup, we're done
68 			 */
69 			break;
70 		}
71 
72 		/*
73 		 * Getting here, means that we have come out of WFI without
74 		 * having been woken up - this shouldn't happen
75 		 *
76 		 * Just note it happening - when we're woken, we can report
77 		 * its occurrence.
78 		 */
79 		(*spurious)++;
80 	}
81 }
82 
83 /*
84  * platform-specific code to shutdown a CPU
85  *
86  * Called with IRQs disabled
87  */
vexpress_cpu_die(unsigned int cpu)88 void __ref vexpress_cpu_die(unsigned int cpu)
89 {
90 	int spurious = 0;
91 
92 	/*
93 	 * we're ready for shutdown now, so do it
94 	 */
95 	cpu_enter_lowpower();
96 	platform_do_lowpower(cpu, &spurious);
97 
98 	/*
99 	 * bring this CPU back into the world of cache
100 	 * coherency, and then restore interrupts
101 	 */
102 	cpu_leave_lowpower();
103 
104 	if (spurious)
105 		pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
106 }
107