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#define pr_fmt(fmt) "suspend: " fmt
  8
  9#include <linux/ftrace.h>
 10#include <linux/suspend.h>
 11#include <asm/csr.h>
 12#include <asm/sbi.h>
 13#include <asm/suspend.h>
 14
 15void suspend_save_csrs(struct suspend_context *context)
 16{
 17	context->scratch = csr_read(CSR_SCRATCH);
 18	if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_XLINUXENVCFG))
 19		context->envcfg = csr_read(CSR_ENVCFG);
 20	context->tvec = csr_read(CSR_TVEC);
 21	context->ie = csr_read(CSR_IE);
 22
 23	/*
 24	 * No need to save/restore IP CSR (i.e. MIP or SIP) because:
 25	 *
 26	 * 1. For no-MMU (M-mode) kernel, the bits in MIP are set by
 27	 *    external devices (such as interrupt controller, timer, etc).
 28	 * 2. For MMU (S-mode) kernel, the bits in SIP are set by
 29	 *    M-mode firmware and external devices (such as interrupt
 30	 *    controller, etc).
 31	 */
 32
 33#ifdef CONFIG_MMU
 34	context->satp = csr_read(CSR_SATP);
 35#endif
 36}
 37
 38void suspend_restore_csrs(struct suspend_context *context)
 39{
 40	csr_write(CSR_SCRATCH, context->scratch);
 41	if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_XLINUXENVCFG))
 42		csr_write(CSR_ENVCFG, context->envcfg);
 43	csr_write(CSR_TVEC, context->tvec);
 44	csr_write(CSR_IE, context->ie);
 45
 46#ifdef CONFIG_MMU
 47	csr_write(CSR_SATP, context->satp);
 48#endif
 49}
 50
 51int cpu_suspend(unsigned long arg,
 52		int (*finish)(unsigned long arg,
 53			      unsigned long entry,
 54			      unsigned long context))
 55{
 56	int rc = 0;
 57	struct suspend_context context = { 0 };
 58
 59	/* Finisher should be non-NULL */
 60	if (!finish)
 61		return -EINVAL;
 62
 63	/* Save additional CSRs*/
 64	suspend_save_csrs(&context);
 65
 66	/*
 67	 * Function graph tracer state gets incosistent when the kernel
 68	 * calls functions that never return (aka finishers) hence disable
 69	 * graph tracing during their execution.
 70	 */
 71	pause_graph_tracing();
 72
 73	/* Save context on stack */
 74	if (__cpu_suspend_enter(&context)) {
 75		/* Call the finisher */
 76		rc = finish(arg, __pa_symbol(__cpu_resume_enter),
 77			    (ulong)&context);
 78
 79		/*
 80		 * Should never reach here, unless the suspend finisher
 81		 * fails. Successful cpu_suspend() should return from
 82		 * __cpu_resume_entry()
 83		 */
 84		if (!rc)
 85			rc = -EOPNOTSUPP;
 86	}
 87
 88	/* Enable function graph tracer */
 89	unpause_graph_tracing();
 90
 91	/* Restore additional CSRs */
 92	suspend_restore_csrs(&context);
 93
 94	return rc;
 95}
 96
 97#ifdef CONFIG_RISCV_SBI
 98static int sbi_system_suspend(unsigned long sleep_type,
 99			      unsigned long resume_addr,
100			      unsigned long opaque)
101{
102	struct sbiret ret;
103
104	ret = sbi_ecall(SBI_EXT_SUSP, SBI_EXT_SUSP_SYSTEM_SUSPEND,
105			sleep_type, resume_addr, opaque, 0, 0, 0);
106	if (ret.error)
107		return sbi_err_map_linux_errno(ret.error);
108
109	return ret.value;
110}
111
112static int sbi_system_suspend_enter(suspend_state_t state)
113{
114	return cpu_suspend(SBI_SUSP_SLEEP_TYPE_SUSPEND_TO_RAM, sbi_system_suspend);
115}
116
117static const struct platform_suspend_ops sbi_system_suspend_ops = {
118	.valid = suspend_valid_only_mem,
119	.enter = sbi_system_suspend_enter,
120};
121
122static int __init sbi_system_suspend_init(void)
123{
124	if (sbi_spec_version >= sbi_mk_version(2, 0) &&
125	    sbi_probe_extension(SBI_EXT_SUSP) > 0) {
126		pr_info("SBI SUSP extension detected\n");
127		if (IS_ENABLED(CONFIG_SUSPEND))
128			suspend_set_ops(&sbi_system_suspend_ops);
129	}
130
131	return 0;
132}
133
134arch_initcall(sbi_system_suspend_init);
135#endif /* CONFIG_RISCV_SBI */