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
20static 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
41static 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
57static 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 */
92void 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

source code of linux/arch/arm/mach-versatile/hotplug.c