xref: /openbmc/linux/arch/mips/kernel/pm.c (revision 2874c5fd)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright (C) 2014 Imagination Technologies Ltd.
4  *
5  * CPU PM notifiers for saving/restoring general CPU state.
6  */
7 
8 #include <linux/cpu_pm.h>
9 #include <linux/init.h>
10 
11 #include <asm/dsp.h>
12 #include <asm/fpu.h>
13 #include <asm/mmu_context.h>
14 #include <asm/pm.h>
15 #include <asm/watch.h>
16 
17 /* Used by PM helper macros in asm/pm.h */
18 struct mips_static_suspend_state mips_static_suspend_state;
19 
20 /**
21  * mips_cpu_save() - Save general CPU state.
22  * Ensures that general CPU context is saved, notably FPU and DSP.
23  */
mips_cpu_save(void)24 static int mips_cpu_save(void)
25 {
26 	/* Save FPU state */
27 	lose_fpu(1);
28 
29 	/* Save DSP state */
30 	save_dsp(current);
31 
32 	return 0;
33 }
34 
35 /**
36  * mips_cpu_restore() - Restore general CPU state.
37  * Restores important CPU context.
38  */
mips_cpu_restore(void)39 static void mips_cpu_restore(void)
40 {
41 	unsigned int cpu = smp_processor_id();
42 
43 	/* Restore ASID */
44 	if (current->mm)
45 		write_c0_entryhi(cpu_asid(cpu, current->mm));
46 
47 	/* Restore DSP state */
48 	restore_dsp(current);
49 
50 	/* Restore UserLocal */
51 	if (cpu_has_userlocal)
52 		write_c0_userlocal(current_thread_info()->tp_value);
53 
54 	/* Restore watch registers */
55 	__restore_watch(current);
56 }
57 
58 /**
59  * mips_pm_notifier() - Notifier for preserving general CPU context.
60  * @self:	Notifier block.
61  * @cmd:	CPU PM event.
62  * @v:		Private data (unused).
63  *
64  * This is called when a CPU power management event occurs, and is used to
65  * ensure that important CPU context is preserved across a CPU power down.
66  */
mips_pm_notifier(struct notifier_block * self,unsigned long cmd,void * v)67 static int mips_pm_notifier(struct notifier_block *self, unsigned long cmd,
68 			    void *v)
69 {
70 	int ret;
71 
72 	switch (cmd) {
73 	case CPU_PM_ENTER:
74 		ret = mips_cpu_save();
75 		if (ret)
76 			return NOTIFY_STOP;
77 		break;
78 	case CPU_PM_ENTER_FAILED:
79 	case CPU_PM_EXIT:
80 		mips_cpu_restore();
81 		break;
82 	}
83 
84 	return NOTIFY_OK;
85 }
86 
87 static struct notifier_block mips_pm_notifier_block = {
88 	.notifier_call = mips_pm_notifier,
89 };
90 
mips_pm_init(void)91 static int __init mips_pm_init(void)
92 {
93 	return cpu_pm_register_notifier(&mips_pm_notifier_block);
94 }
95 arch_initcall(mips_pm_init);
96