Linux Kernel  3.7.1
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
hotplug.c
Go to the documentation of this file.
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/cacheflush.h>
16 #include <asm/smp_plat.h>
17 #include <asm/cp15.h>
18 
19 static inline void cpu_enter_lowpower(void)
20 {
21  unsigned int v;
22 
24  asm volatile(
25  "mcr p15, 0, %1, c7, c5, 0\n"
26  " mcr p15, 0, %1, c7, c10, 4\n"
27  /*
28  * Turn off coherency
29  */
30  " mrc p15, 0, %0, c1, c0, 1\n"
31  " bic %0, %0, %3\n"
32  " mcr p15, 0, %0, c1, c0, 1\n"
33  " mrc p15, 0, %0, c1, c0, 0\n"
34  " bic %0, %0, %2\n"
35  " mcr p15, 0, %0, c1, c0, 0\n"
36  : "=&r" (v)
37  : "r" (0), "Ir" (CR_C), "Ir" (0x40)
38  : "cc");
39 }
40 
41 static inline void cpu_leave_lowpower(void)
42 {
43  unsigned int v;
44 
45  asm volatile(
46  "mrc p15, 0, %0, c1, c0, 0\n"
47  " orr %0, %0, %1\n"
48  " mcr p15, 0, %0, c1, c0, 0\n"
49  " mrc p15, 0, %0, c1, c0, 1\n"
50  " orr %0, %0, %2\n"
51  " mcr p15, 0, %0, c1, c0, 1\n"
52  : "=&r" (v)
53  : "Ir" (CR_C), "Ir" (0x40)
54  : "cc");
55 }
56 
57 static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
58 {
59  /*
60  * there is no power-control hardware on this platform, so all
61  * we can do is put the core into WFI; this is safe as the calling
62  * code will have already disabled interrupts
63  */
64  for (;;) {
65  wfi();
66 
67  if (pen_release == cpu_logical_map(cpu)) {
68  /*
69  * OK, proper wakeup, we're done
70  */
71  break;
72  }
73 
74  /*
75  * Getting here, means that we have come out of WFI without
76  * having been woken up - this shouldn't happen
77  *
78  * Just note it happening - when we're woken, we can report
79  * its occurrence.
80  */
81  (*spurious)++;
82  }
83 }
84 
85 /*
86  * platform-specific code to shutdown a CPU
87  *
88  * Called with IRQs disabled
89  */
90 void __ref vexpress_cpu_die(unsigned int cpu)
91 {
92  int spurious = 0;
93 
94  /*
95  * we're ready for shutdown now, so do it
96  */
97  cpu_enter_lowpower();
98  platform_do_lowpower(cpu, &spurious);
99 
100  /*
101  * bring this CPU back into the world of cache
102  * coherency, and then restore interrupts
103  */
104  cpu_leave_lowpower();
105 
106  if (spurious)
107  pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, spurious);
108 }