1// SPDX-License-Identifier: GPL-2.0-only
 2/*
 3 * Copyright (c) 2021 Western Digital Corporation or its affiliates.
 4 * Copyright (c) 2022 Ventana Micro Systems Inc.
 5 */
 6
 7#include <linux/ftrace.h>
 8#include <asm/csr.h>
 9#include <asm/suspend.h>
10
11static void suspend_save_csrs(struct suspend_context *context)
12{
13	context->scratch = csr_read(CSR_SCRATCH);
14	context->tvec = csr_read(CSR_TVEC);
15	context->ie = csr_read(CSR_IE);
16
17	/*
18	 * No need to save/restore IP CSR (i.e. MIP or SIP) because:
19	 *
20	 * 1. For no-MMU (M-mode) kernel, the bits in MIP are set by
21	 *    external devices (such as interrupt controller, timer, etc).
22	 * 2. For MMU (S-mode) kernel, the bits in SIP are set by
23	 *    M-mode firmware and external devices (such as interrupt
24	 *    controller, etc).
25	 */
26
27#ifdef CONFIG_MMU
28	context->satp = csr_read(CSR_SATP);
29#endif
30}
31
32static void suspend_restore_csrs(struct suspend_context *context)
33{
34	csr_write(CSR_SCRATCH, context->scratch);
35	csr_write(CSR_TVEC, context->tvec);
36	csr_write(CSR_IE, context->ie);
37
38#ifdef CONFIG_MMU
39	csr_write(CSR_SATP, context->satp);
40#endif
41}
42
43int cpu_suspend(unsigned long arg,
44		int (*finish)(unsigned long arg,
45			      unsigned long entry,
46			      unsigned long context))
47{
48	int rc = 0;
49	struct suspend_context context = { 0 };
50
51	/* Finisher should be non-NULL */
52	if (!finish)
53		return -EINVAL;
54
55	/* Save additional CSRs*/
56	suspend_save_csrs(&context);
57
58	/*
59	 * Function graph tracer state gets incosistent when the kernel
60	 * calls functions that never return (aka finishers) hence disable
61	 * graph tracing during their execution.
62	 */
63	pause_graph_tracing();
64
65	/* Save context on stack */
66	if (__cpu_suspend_enter(&context)) {
67		/* Call the finisher */
68		rc = finish(arg, __pa_symbol(__cpu_resume_enter),
69			    (ulong)&context);
70
71		/*
72		 * Should never reach here, unless the suspend finisher
73		 * fails. Successful cpu_suspend() should return from
74		 * __cpu_resume_entry()
75		 */
76		if (!rc)
77			rc = -EOPNOTSUPP;
78	}
79
80	/* Enable function graph tracer */
81	unpause_graph_tracing();
82
83	/* Restore additional CSRs */
84	suspend_restore_csrs(&context);
85
86	return rc;
87}