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 
versatile_immitation_enter_lowpower(unsigned int actrl_mask)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 
versatile_immitation_leave_lowpower(unsigned int actrl_mask)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 
versatile_immitation_do_lowpower(unsigned int cpu,int * spurious)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  */
versatile_immitation_cpu_die(unsigned int cpu,unsigned int actrl_mask)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);
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