1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * Copyright (C) 2002 ARM Ltd. |
4 | * All Rights Reserved |
5 | * |
6 | * This hotplug implementation is _specific_ to the situation found on |
7 | * ARM development platforms where there is _no_ possibility of actually |
8 | * taking a CPU offline, resetting it, or otherwise. Real platforms must |
9 | * NOT copy this code. |
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 | |
18 | #include "platsmp.h" |
19 | |
20 | static inline void versatile_immitation_enter_lowpower(unsigned int actrl_mask) |
21 | { |
22 | unsigned int v; |
23 | |
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" (actrl_mask) |
38 | : "cc" ); |
39 | } |
40 | |
41 | static inline void versatile_immitation_leave_lowpower(unsigned int actrl_mask) |
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" (actrl_mask) |
54 | : "cc" ); |
55 | } |
56 | |
57 | static inline void versatile_immitation_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 | * This code should not be used outside Versatile platforms. |
65 | */ |
66 | for (;;) { |
67 | wfi(); |
68 | |
69 | if (versatile_cpu_release == cpu_logical_map(cpu)) { |
70 | /* |
71 | * OK, proper wakeup, we're done |
72 | */ |
73 | break; |
74 | } |
75 | |
76 | /* |
77 | * Getting here, means that we have come out of WFI without |
78 | * having been woken up - this shouldn't happen |
79 | * |
80 | * Just note it happening - when we're woken, we can report |
81 | * its occurrence. |
82 | */ |
83 | (*spurious)++; |
84 | } |
85 | } |
86 | |
87 | /* |
88 | * platform-specific code to shutdown a CPU. |
89 | * This code supports immitation-style CPU hotplug for Versatile/Realview/ |
90 | * Versatile Express platforms that are unable to do real CPU hotplug. |
91 | */ |
92 | void versatile_immitation_cpu_die(unsigned int cpu, unsigned int actrl_mask) |
93 | { |
94 | int spurious = 0; |
95 | |
96 | versatile_immitation_enter_lowpower(actrl_mask); |
97 | versatile_immitation_do_lowpower(cpu, spurious: &spurious); |
98 | versatile_immitation_leave_lowpower(actrl_mask); |
99 | |
100 | if (spurious) |
101 | pr_warn("CPU%u: %u spurious wakeup calls\n" , cpu, spurious); |
102 | } |
103 | |