/* SPDX-License-Identifier: GPL-2.0-only */
/*
 *  linux/arch/arm/lib/csumpartialcopygeneric.S
 *
 *  Copyright (C) 1995-2001 Russell King
 */
#include <asm/assembler.h>

/*
 * unsigned int
 * csum_partial_copy_xxx(const char *src, char *dst, int len, int sum, )
 *  r0 = src, r1 = dst, r2 = len, r3 = sum
 *  Returns : r0 = checksum
 *
 * Note that 'tst' and 'teq' preserve the carry flag.
 */

src     .req    r0
dst     .req    r1
len     .req    r2
sum     .req    r3

.Lzero:         mov     r0, sum
                load_regs

                /*
                 * Align an unaligned destination pointer.  We know that
                 * we have >= 8 bytes here, so we don't need to check
                 * the length.  Note that the source pointer hasn't been
                 * aligned yet.
                 */
.Ldst_unaligned:
                tst     dst, #1
                beq     .Ldst_16bit

                load1b  ip
                sub     len, len, #1
                adcs    sum, sum, ip, put_byte_1        @ update checksum
                strb    ip, [dst], #1
                tst     dst, #2
                reteq   lr                      @ dst is now 32bit aligned

.Ldst_16bit:    load2b  r8, ip
                sub     len, len, #2
                adcs    sum, sum, r8, put_byte_0
                strb    r8, [dst], #1
                adcs    sum, sum, ip, put_byte_1
                strb    ip, [dst], #1
                ret     lr                      @ dst is now 32bit aligned

                /*
                 * Handle 0 to 7 bytes, with any alignment of source and
                 * destination pointers.  Note that when we get here, C = 0
                 */
.Lless8:        teq     len, #0                 @ check for zero count
                beq     .Lzero

                /* we must have at least one byte. */
                tst     dst, #1                 @ dst 16-bit aligned
                beq     .Lless8_aligned

                /* Align dst */
                load1b  ip
                sub     len, len, #1
                adcs    sum, sum, ip, put_byte_1        @ update checksum
                strb    ip, [dst], #1
                tst     len, #6
                beq     .Lless8_byteonly

1:              load2b  r8, ip
                sub     len, len, #2
                adcs    sum, sum, r8, put_byte_0
                strb    r8, [dst], #1
                adcs    sum, sum, ip, put_byte_1
                strb    ip, [dst], #1
.Lless8_aligned:
                tst     len, #6
                bne     1b
.Lless8_byteonly:
                tst     len, #1
                beq     .Ldone
                load1b  r8
                adcs    sum, sum, r8, put_byte_0        @ update checksum
                strb    r8, [dst], #1
                b       .Ldone

FN_ENTRY
                save_regs
                mov     sum, #-1

                cmp     len, #8                 @ Ensure that we have at least
                blo     .Lless8                 @ 8 bytes to copy.

                adds    sum, sum, #0            @ C = 0
                tst     dst, #3                 @ Test destination alignment
                blne    .Ldst_unaligned         @ align destination, return here

                /*
                 * Ok, the dst pointer is now 32bit aligned, and we know
                 * that we must have more than 4 bytes to copy.  Note
                 * that C contains the carry from the dst alignment above.
                 */

                tst     src, #3                 @ Test source alignment
                bne     .Lsrc_not_aligned

                /* Routine for src & dst aligned */

                bics    ip, len, #15
                beq     2f

1:              load4l  r4, r5, r6, r7
                stmia   dst!, {r4, r5, r6, r7}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                adcs    sum, sum, r6
                adcs    sum, sum, r7
                sub     ip, ip, #16
                teq     ip, #0
                bne     1b

2:              ands    ip, len, #12
                beq     4f
                tst     ip, #8
                beq     3f
                load2l  r4, r5
                stmia   dst!, {r4, r5}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                tst     ip, #4
                beq     4f

3:              load1l  r4
                str     r4, [dst], #4
                adcs    sum, sum, r4

4:              ands    len, len, #3
                beq     .Ldone
                load1l  r4
                tst     len, #2
                mov     r5, r4, get_byte_0
                beq     .Lexit
                adcs    sum, sum, r4, lspush #16
                strb    r5, [dst], #1
                mov     r5, r4, get_byte_1
                strb    r5, [dst], #1
                mov     r5, r4, get_byte_2
.Lexit:         tst     len, #1
                strbne  r5, [dst], #1
                andne   r5, r5, #255
                adcsne  sum, sum, r5, put_byte_0

                /*
                 * If the dst pointer was not 16-bit aligned, we
                 * need to rotate the checksum here to get around
                 * the inefficient byte manipulations in the
                 * architecture independent code.
                 */
.Ldone:         adc     r0, sum, #0
                ldr     sum, [sp, #0]           @ dst
                tst     sum, #1
                movne   r0, r0, ror #8
                load_regs

.Lsrc_not_aligned:
                adc     sum, sum, #0            @ include C from dst alignment
                and     ip, src, #3
                bic     src, src, #3
                load1l  r5
                cmp     ip, #2
                beq     .Lsrc2_aligned
                bhi     .Lsrc3_aligned
                mov     r4, r5, lspull #8               @ C = 0
                bics    ip, len, #15
                beq     2f
1:              load4l  r5, r6, r7, r8
                orr     r4, r4, r5, lspush #24
                mov     r5, r5, lspull #8
                orr     r5, r5, r6, lspush #24
                mov     r6, r6, lspull #8
                orr     r6, r6, r7, lspush #24
                mov     r7, r7, lspull #8
                orr     r7, r7, r8, lspush #24
                stmia   dst!, {r4, r5, r6, r7}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                adcs    sum, sum, r6
                adcs    sum, sum, r7
                mov     r4, r8, lspull #8
                sub     ip, ip, #16
                teq     ip, #0
                bne     1b
2:              ands    ip, len, #12
                beq     4f
                tst     ip, #8
                beq     3f
                load2l  r5, r6
                orr     r4, r4, r5, lspush #24
                mov     r5, r5, lspull #8
                orr     r5, r5, r6, lspush #24
                stmia   dst!, {r4, r5}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                mov     r4, r6, lspull #8
                tst     ip, #4
                beq     4f
3:              load1l  r5
                orr     r4, r4, r5, lspush #24
                str     r4, [dst], #4
                adcs    sum, sum, r4
                mov     r4, r5, lspull #8
4:              ands    len, len, #3
                beq     .Ldone
                mov     r5, r4, get_byte_0
                tst     len, #2
                beq     .Lexit
                adcs    sum, sum, r4, lspush #16
                strb    r5, [dst], #1
                mov     r5, r4, get_byte_1
                strb    r5, [dst], #1
                mov     r5, r4, get_byte_2
                b       .Lexit

.Lsrc2_aligned: mov     r4, r5, lspull #16
                adds    sum, sum, #0
                bics    ip, len, #15
                beq     2f
1:              load4l  r5, r6, r7, r8
                orr     r4, r4, r5, lspush #16
                mov     r5, r5, lspull #16
                orr     r5, r5, r6, lspush #16
                mov     r6, r6, lspull #16
                orr     r6, r6, r7, lspush #16
                mov     r7, r7, lspull #16
                orr     r7, r7, r8, lspush #16
                stmia   dst!, {r4, r5, r6, r7}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                adcs    sum, sum, r6
                adcs    sum, sum, r7
                mov     r4, r8, lspull #16
                sub     ip, ip, #16
                teq     ip, #0
                bne     1b
2:              ands    ip, len, #12
                beq     4f
                tst     ip, #8
                beq     3f
                load2l  r5, r6
                orr     r4, r4, r5, lspush #16
                mov     r5, r5, lspull #16
                orr     r5, r5, r6, lspush #16
                stmia   dst!, {r4, r5}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                mov     r4, r6, lspull #16
                tst     ip, #4
                beq     4f
3:              load1l  r5
                orr     r4, r4, r5, lspush #16
                str     r4, [dst], #4
                adcs    sum, sum, r4
                mov     r4, r5, lspull #16
4:              ands    len, len, #3
                beq     .Ldone
                mov     r5, r4, get_byte_0
                tst     len, #2
                beq     .Lexit
                adcs    sum, sum, r4
                strb    r5, [dst], #1
                mov     r5, r4, get_byte_1
                strb    r5, [dst], #1
                tst     len, #1
                beq     .Ldone
                load1b  r5
                b       .Lexit

.Lsrc3_aligned: mov     r4, r5, lspull #24
                adds    sum, sum, #0
                bics    ip, len, #15
                beq     2f
1:              load4l  r5, r6, r7, r8
                orr     r4, r4, r5, lspush #8
                mov     r5, r5, lspull #24
                orr     r5, r5, r6, lspush #8
                mov     r6, r6, lspull #24
                orr     r6, r6, r7, lspush #8
                mov     r7, r7, lspull #24
                orr     r7, r7, r8, lspush #8
                stmia   dst!, {r4, r5, r6, r7}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                adcs    sum, sum, r6
                adcs    sum, sum, r7
                mov     r4, r8, lspull #24
                sub     ip, ip, #16
                teq     ip, #0
                bne     1b
2:              ands    ip, len, #12
                beq     4f
                tst     ip, #8
                beq     3f
                load2l  r5, r6
                orr     r4, r4, r5, lspush #8
                mov     r5, r5, lspull #24
                orr     r5, r5, r6, lspush #8
                stmia   dst!, {r4, r5}
                adcs    sum, sum, r4
                adcs    sum, sum, r5
                mov     r4, r6, lspull #24
                tst     ip, #4
                beq     4f
3:              load1l  r5
                orr     r4, r4, r5, lspush #8
                str     r4, [dst], #4
                adcs    sum, sum, r4
                mov     r4, r5, lspull #24
4:              ands    len, len, #3
                beq     .Ldone
                mov     r5, r4, get_byte_0
                tst     len, #2
                beq     .Lexit
                strb    r5, [dst], #1
                adcs    sum, sum, r4
                load1l  r4
                mov     r5, r4, get_byte_0
                strb    r5, [dst], #1
                adcs    sum, sum, r4, lspush #24
                mov     r5, r4, get_byte_1
                b       .Lexit
FN_EXIT