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);
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