/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Hibernation low level support for RISCV.
 *
 * Copyright (C) 2023 StarFive Technology Co., Ltd.
 *
 * Author: Jee Heng Sia <jeeheng.sia@starfivetech.com>
 */

#include <asm/asm.h>
#include <asm/asm-offsets.h>
#include <asm/assembler.h>
#include <asm/csr.h>

#include <linux/linkage.h>

/*
 * int __hibernate_cpu_resume(void)
 * Switch back to the hibernated image's page table prior to restoring the CPU
 * context.
 *
 * Always returns 0
 */
SYM_FUNC_START(__hibernate_cpu_resume)
        /* switch to hibernated image's page table. */
        csrw CSR_SATP, s0
        sfence.vma

        REG_L   a0, hibernate_cpu_context

        suspend_restore_regs

        /* Return zero value. */
        mv      a0, zero

        ret
SYM_FUNC_END(__hibernate_cpu_resume)

/*
 * Prepare to restore the image.
 * a0: satp of saved page tables.
 * a1: satp of temporary page tables.
 * a2: cpu_resume.
 */
SYM_FUNC_START(hibernate_restore_image)
        mv      s0, a0
        mv      s1, a1
        mv      s2, a2
        REG_L   s4, restore_pblist
        REG_L   a1, relocated_restore_code

        jr      a1
SYM_FUNC_END(hibernate_restore_image)

/*
 * The below code will be executed from a 'safe' page.
 * It first switches to the temporary page table, then starts to copy the pages
 * back to the original memory location. Finally, it jumps to __hibernate_cpu_resume()
 * to restore the CPU context.
 */
SYM_FUNC_START(hibernate_core_restore_code)
        /* switch to temp page table. */
        csrw satp, s1
        sfence.vma
.Lcopy:
        /* The below code will restore the hibernated image. */
        REG_L   a1, HIBERN_PBE_ADDR(s4)
        REG_L   a0, HIBERN_PBE_ORIG(s4)

        copy_page a0, a1

        REG_L   s4, HIBERN_PBE_NEXT(s4)
        bnez    s4, .Lcopy

        jr      s2
SYM_FUNC_END(hibernate_core_restore_code)