/* SPDX-License-Identifier: GPL-2.0 */
/*
 * relocate_kernel.S for kexec
 *
 * Copyright (C) 2022 Loongson Technology Corporation Limited
 */

#include <linux/kexec.h>

#include <asm/asm.h>
#include <asm/asmmacro.h>
#include <asm/regdef.h>
#include <asm/loongarch.h>
#include <asm/stackframe.h>
#include <asm/addrspace.h>

SYM_CODE_START(relocate_new_kernel)
        UNWIND_HINT_UNDEFINED
        /*
         * a0: EFI boot flag for the new kernel
         * a1: Command line pointer for the new kernel
         * a2: System table pointer for the new kernel
         * a3: Start address to jump to after relocation
         * a4: Pointer to the current indirection page entry
         */
        move            s0, a4

        /*
         * In case of a kdump/crash kernel, the indirection page is not
         * populated as the kernel is directly copied to a reserved location
         */
        beqz            s0, done

process_entry:
        PTR_L           s1, s0, 0
        PTR_ADDI        s0, s0, SZREG

        /* destination page */
        andi            s2, s1, IND_DESTINATION
        beqz            s2, 1f
        li.w            t0, ~0x1
        and             s3, s1, t0      /* store destination addr in s3 */
        b               process_entry

1:
        /* indirection page, update s0  */
        andi            s2, s1, IND_INDIRECTION
        beqz            s2, 1f
        li.w            t0, ~0x2
        and             s0, s1, t0
        b               process_entry

1:
        /* done page */
        andi            s2, s1, IND_DONE
        beqz            s2, 1f
        b               done

1:
        /* source page */
        andi            s2, s1, IND_SOURCE
        beqz            s2, process_entry
        li.w            t0, ~0x8
        and             s1, s1, t0
        li.w            s5, (1 << _PAGE_SHIFT) / SZREG

copy_word:
        /* copy page word by word */
        REG_L           s4, s1, 0
        REG_S           s4, s3, 0
        PTR_ADDI        s3, s3, SZREG
        PTR_ADDI        s1, s1, SZREG
        LONG_ADDI       s5, s5, -1
        beqz            s5, process_entry
        b               copy_word

done:
        ibar            0
        dbar            0

        /*
         * Jump to the new kernel,
         * make sure the values of a0, a1, a2 and a3 are not changed.
         */
        jr              a3
SYM_CODE_END(relocate_new_kernel)

#ifdef CONFIG_SMP
/*
 * Other CPUs should wait until code is relocated and
 * then start at the entry point from LOONGARCH_IOCSR_MBUF0.
 */
SYM_CODE_START(kexec_smp_wait)
        UNWIND_HINT_UNDEFINED
1:      li.w            t0, 0x100                       /* wait for init loop */
2:      addi.w          t0, t0, -1                      /* limit mailbox access */
        bnez            t0, 2b
        li.w            t1, LOONGARCH_IOCSR_MBUF0
        iocsrrd.w       s0, t1                          /* check PC as an indicator */
        beqz            s0, 1b
        iocsrrd.d       s0, t1                          /* get PC via mailbox */

        li.d            t0, CACHE_BASE
        or              s0, s0, t0                      /* s0 = TO_CACHE(s0) */
        jr              s0                              /* jump to initial PC */
SYM_CODE_END(kexec_smp_wait)
#endif

relocate_new_kernel_end:

        .section ".data"
SYM_DATA(relocate_new_kernel_size, .quad relocate_new_kernel_end - relocate_new_kernel)