/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Core of the accelerated CRC algorithm.
 * In your file, define the constants and CRC_FUNCTION_NAME
 * Then include this file.
 *
 * Calculate the checksum of data that is 16 byte aligned and a multiple of
 * 16 bytes.
 *
 * The first step is to reduce it to 1024 bits. We do this in 8 parallel
 * chunks in order to mask the latency of the vpmsum instructions. If we
 * have more than 32 kB of data to checksum we repeat this step multiple
 * times, passing in the previous 1024 bits.
 *
 * The next step is to reduce the 1024 bits to 64 bits. This step adds
 * 32 bits of 0s to the end - this matches what a CRC does. We just
 * calculate constants that land the data in this 32 bits.
 *
 * We then use fixed point Barrett reduction to compute a mod n over GF(2)
 * for n = CRC using POWER8 instructions. We use x = 32.
 *
 * https://en.wikipedia.org/wiki/Barrett_reduction
 *
 * Copyright (C) 2015 Anton Blanchard <anton@au.ibm.com>, IBM
*/

#include <asm/ppc_asm.h>
#include <asm/ppc-opcode.h>

#define MAX_SIZE        32768

        .text

#if defined(__BIG_ENDIAN__) && defined(REFLECT)
#define BYTESWAP_DATA
#elif defined(__LITTLE_ENDIAN__) && !defined(REFLECT)
#define BYTESWAP_DATA
#else
#undef BYTESWAP_DATA
#endif

#define off16           r25
#define off32           r26
#define off48           r27
#define off64           r28
#define off80           r29
#define off96           r30
#define off112          r31

#define const1          v24
#define const2          v25

#define byteswap        v26
#define mask_32bit      v27
#define mask_64bit      v28
#define zeroes          v29

#ifdef BYTESWAP_DATA
#define VPERM(A, B, C, D) vperm A, B, C, D
#else
#define VPERM(A, B, C, D)
#endif

/* unsigned int CRC_FUNCTION_NAME(unsigned int crc, void *p, unsigned long len) */
FUNC_START(CRC_FUNCTION_NAME)
        std     r31,-8(r1)
        std     r30,-16(r1)
        std     r29,-24(r1)
        std     r28,-32(r1)
        std     r27,-40(r1)
        std     r26,-48(r1)
        std     r25,-56(r1)

        li      off16,16
        li      off32,32
        li      off48,48
        li      off64,64
        li      off80,80
        li      off96,96
        li      off112,112
        li      r0,0

        /* Enough room for saving 10 non volatile VMX registers */
        subi    r6,r1,56+10*16
        subi    r7,r1,56+2*16

        stvx    v20,0,r6
        stvx    v21,off16,r6
        stvx    v22,off32,r6
        stvx    v23,off48,r6
        stvx    v24,off64,r6
        stvx    v25,off80,r6
        stvx    v26,off96,r6
        stvx    v27,off112,r6
        stvx    v28,0,r7
        stvx    v29,off16,r7

        mr      r10,r3

        vxor    zeroes,zeroes,zeroes
        vspltisw v0,-1

        vsldoi  mask_32bit,zeroes,v0,4
        vsldoi  mask_64bit,zeroes,v0,8

        /* Get the initial value into v8 */
        vxor    v8,v8,v8
        MTVRD(v8, R3)
#ifdef REFLECT
        vsldoi  v8,zeroes,v8,8  /* shift into bottom 32 bits */
#else
        vsldoi  v8,v8,zeroes,4  /* shift into top 32 bits */
#endif

#ifdef BYTESWAP_DATA
        LOAD_REG_ADDR(r3, .byteswap_constant)
        lvx     byteswap,0,r3
        addi    r3,r3,16
#endif

        cmpdi   r5,256
        blt     .Lshort

        rldicr  r6,r5,0,56

        /* Checksum in blocks of MAX_SIZE */
1:      lis     r7,MAX_SIZE@h
        ori     r7,r7,MAX_SIZE@l
        mr      r9,r7
        cmpd    r6,r7
        bgt     2f
        mr      r7,r6
2:      subf    r6,r7,r6

        /* our main loop does 128 bytes at a time */
        srdi    r7,r7,7

        /*
         * Work out the offset into the constants table to start at. Each
         * constant is 16 bytes, and it is used against 128 bytes of input
         * data - 128 / 16 = 8
         */
        sldi    r8,r7,4
        srdi    r9,r9,3
        subf    r8,r8,r9

        /* We reduce our final 128 bytes in a separate step */
        addi    r7,r7,-1
        mtctr   r7

        LOAD_REG_ADDR(r3, .constants)

        /* Find the start of our constants */
        add     r3,r3,r8

        /* zero v0-v7 which will contain our checksums */
        vxor    v0,v0,v0
        vxor    v1,v1,v1
        vxor    v2,v2,v2
        vxor    v3,v3,v3
        vxor    v4,v4,v4
        vxor    v5,v5,v5
        vxor    v6,v6,v6
        vxor    v7,v7,v7

        lvx     const1,0,r3

        /*
         * If we are looping back to consume more data we use the values
         * already in v16-v23.
         */
        cmpdi   r0,1
        beq     2f

        /* First warm up pass */
        lvx     v16,0,r4
        lvx     v17,off16,r4
        VPERM(v16,v16,v16,byteswap)
        VPERM(v17,v17,v17,byteswap)
        lvx     v18,off32,r4
        lvx     v19,off48,r4
        VPERM(v18,v18,v18,byteswap)
        VPERM(v19,v19,v19,byteswap)
        lvx     v20,off64,r4
        lvx     v21,off80,r4
        VPERM(v20,v20,v20,byteswap)
        VPERM(v21,v21,v21,byteswap)
        lvx     v22,off96,r4
        lvx     v23,off112,r4
        VPERM(v22,v22,v22,byteswap)
        VPERM(v23,v23,v23,byteswap)
        addi    r4,r4,8*16

        /* xor in initial value */
        vxor    v16,v16,v8

2:      bdz     .Lfirst_warm_up_done

        addi    r3,r3,16
        lvx     const2,0,r3

        /* Second warm up pass */
        VPMSUMD(v8,v16,const1)
        lvx     v16,0,r4
        VPERM(v16,v16,v16,byteswap)
        ori     r2,r2,0

        VPMSUMD(v9,v17,const1)
        lvx     v17,off16,r4
        VPERM(v17,v17,v17,byteswap)
        ori     r2,r2,0

        VPMSUMD(v10,v18,const1)
        lvx     v18,off32,r4
        VPERM(v18,v18,v18,byteswap)
        ori     r2,r2,0

        VPMSUMD(v11,v19,const1)
        lvx     v19,off48,r4
        VPERM(v19,v19,v19,byteswap)
        ori     r2,r2,0

        VPMSUMD(v12,v20,const1)
        lvx     v20,off64,r4
        VPERM(v20,v20,v20,byteswap)
        ori     r2,r2,0

        VPMSUMD(v13,v21,const1)
        lvx     v21,off80,r4
        VPERM(v21,v21,v21,byteswap)
        ori     r2,r2,0

        VPMSUMD(v14,v22,const1)
        lvx     v22,off96,r4
        VPERM(v22,v22,v22,byteswap)
        ori     r2,r2,0

        VPMSUMD(v15,v23,const1)
        lvx     v23,off112,r4
        VPERM(v23,v23,v23,byteswap)

        addi    r4,r4,8*16

        bdz     .Lfirst_cool_down

        /*
         * main loop. We modulo schedule it such that it takes three iterations
         * to complete - first iteration load, second iteration vpmsum, third
         * iteration xor.
         */
        .balign 16
4:      lvx     const1,0,r3
        addi    r3,r3,16
        ori     r2,r2,0

        vxor    v0,v0,v8
        VPMSUMD(v8,v16,const2)
        lvx     v16,0,r4
        VPERM(v16,v16,v16,byteswap)
        ori     r2,r2,0

        vxor    v1,v1,v9
        VPMSUMD(v9,v17,const2)
        lvx     v17,off16,r4
        VPERM(v17,v17,v17,byteswap)
        ori     r2,r2,0

        vxor    v2,v2,v10
        VPMSUMD(v10,v18,const2)
        lvx     v18,off32,r4
        VPERM(v18,v18,v18,byteswap)
        ori     r2,r2,0

        vxor    v3,v3,v11
        VPMSUMD(v11,v19,const2)
        lvx     v19,off48,r4
        VPERM(v19,v19,v19,byteswap)
        lvx     const2,0,r3
        ori     r2,r2,0

        vxor    v4,v4,v12
        VPMSUMD(v12,v20,const1)
        lvx     v20,off64,r4
        VPERM(v20,v20,v20,byteswap)
        ori     r2,r2,0

        vxor    v5,v5,v13
        VPMSUMD(v13,v21,const1)
        lvx     v21,off80,r4
        VPERM(v21,v21,v21,byteswap)
        ori     r2,r2,0

        vxor    v6,v6,v14
        VPMSUMD(v14,v22,const1)
        lvx     v22,off96,r4
        VPERM(v22,v22,v22,byteswap)
        ori     r2,r2,0

        vxor    v7,v7,v15
        VPMSUMD(v15,v23,const1)
        lvx     v23,off112,r4
        VPERM(v23,v23,v23,byteswap)

        addi    r4,r4,8*16

        bdnz    4b

.Lfirst_cool_down:
        /* First cool down pass */
        lvx     const1,0,r3
        addi    r3,r3,16

        vxor    v0,v0,v8
        VPMSUMD(v8,v16,const1)
        ori     r2,r2,0

        vxor    v1,v1,v9
        VPMSUMD(v9,v17,const1)
        ori     r2,r2,0

        vxor    v2,v2,v10
        VPMSUMD(v10,v18,const1)
        ori     r2,r2,0

        vxor    v3,v3,v11
        VPMSUMD(v11,v19,const1)
        ori     r2,r2,0

        vxor    v4,v4,v12
        VPMSUMD(v12,v20,const1)
        ori     r2,r2,0

        vxor    v5,v5,v13
        VPMSUMD(v13,v21,const1)
        ori     r2,r2,0

        vxor    v6,v6,v14
        VPMSUMD(v14,v22,const1)
        ori     r2,r2,0

        vxor    v7,v7,v15
        VPMSUMD(v15,v23,const1)
        ori     r2,r2,0

.Lsecond_cool_down:
        /* Second cool down pass */
        vxor    v0,v0,v8
        vxor    v1,v1,v9
        vxor    v2,v2,v10
        vxor    v3,v3,v11
        vxor    v4,v4,v12
        vxor    v5,v5,v13
        vxor    v6,v6,v14
        vxor    v7,v7,v15

#ifdef REFLECT
        /*
         * vpmsumd produces a 96 bit result in the least significant bits
         * of the register. Since we are bit reflected we have to shift it
         * left 32 bits so it occupies the least significant bits in the
         * bit reflected domain.
         */
        vsldoi  v0,v0,zeroes,4
        vsldoi  v1,v1,zeroes,4
        vsldoi  v2,v2,zeroes,4
        vsldoi  v3,v3,zeroes,4
        vsldoi  v4,v4,zeroes,4
        vsldoi  v5,v5,zeroes,4
        vsldoi  v6,v6,zeroes,4
        vsldoi  v7,v7,zeroes,4
#endif

        /* xor with last 1024 bits */
        lvx     v8,0,r4
        lvx     v9,off16,r4
        VPERM(v8,v8,v8,byteswap)
        VPERM(v9,v9,v9,byteswap)
        lvx     v10,off32,r4
        lvx     v11,off48,r4
        VPERM(v10,v10,v10,byteswap)
        VPERM(v11,v11,v11,byteswap)
        lvx     v12,off64,r4
        lvx     v13,off80,r4
        VPERM(v12,v12,v12,byteswap)
        VPERM(v13,v13,v13,byteswap)
        lvx     v14,off96,r4
        lvx     v15,off112,r4
        VPERM(v14,v14,v14,byteswap)
        VPERM(v15,v15,v15,byteswap)

        addi    r4,r4,8*16

        vxor    v16,v0,v8
        vxor    v17,v1,v9
        vxor    v18,v2,v10
        vxor    v19,v3,v11
        vxor    v20,v4,v12
        vxor    v21,v5,v13
        vxor    v22,v6,v14
        vxor    v23,v7,v15

        li      r0,1
        cmpdi   r6,0
        addi    r6,r6,128
        bne     1b

        /* Work out how many bytes we have left */
        andi.   r5,r5,127

        /* Calculate where in the constant table we need to start */
        subfic  r6,r5,128
        add     r3,r3,r6

        /* How many 16 byte chunks are in the tail */
        srdi    r7,r5,4
        mtctr   r7

        /*
         * Reduce the previously calculated 1024 bits to 64 bits, shifting
         * 32 bits to include the trailing 32 bits of zeros
         */
        lvx     v0,0,r3
        lvx     v1,off16,r3
        lvx     v2,off32,r3
        lvx     v3,off48,r3
        lvx     v4,off64,r3
        lvx     v5,off80,r3
        lvx     v6,off96,r3
        lvx     v7,off112,r3
        addi    r3,r3,8*16

        VPMSUMW(v0,v16,v0)
        VPMSUMW(v1,v17,v1)
        VPMSUMW(v2,v18,v2)
        VPMSUMW(v3,v19,v3)
        VPMSUMW(v4,v20,v4)
        VPMSUMW(v5,v21,v5)
        VPMSUMW(v6,v22,v6)
        VPMSUMW(v7,v23,v7)

        /* Now reduce the tail (0 - 112 bytes) */
        cmpdi   r7,0
        beq     1f

        lvx     v16,0,r4
        lvx     v17,0,r3
        VPERM(v16,v16,v16,byteswap)
        VPMSUMW(v16,v16,v17)
        vxor    v0,v0,v16
        bdz     1f

        lvx     v16,off16,r4
        lvx     v17,off16,r3
        VPERM(v16,v16,v16,byteswap)
        VPMSUMW(v16,v16,v17)
        vxor    v0,v0,v16
        bdz     1f

        lvx     v16,off32,r4
        lvx     v17,off32,r3
        VPERM(v16,v16,v16,byteswap)
        VPMSUMW(v16,v16,v17)
        vxor    v0,v0,v16
        bdz     1f

        lvx     v16,off48,r4
        lvx     v17,off48,r3
        VPERM(v16,v16,v16,byteswap)
        VPMSUMW(v16,v16,v17)
        vxor    v0,v0,v16
        bdz     1f

        lvx     v16,off64,r4
        lvx     v17,off64,r3
        VPERM(v16,v16,v16,byteswap)
        VPMSUMW(v16,v16,v17)
        vxor    v0,v0,v16
        bdz     1f

        lvx     v16,off80,r4
        lvx     v17,off80,r3
        VPERM(v16,v16,v16,byteswap)
        VPMSUMW(v16,v16,v17)
        vxor    v0,v0,v16
        bdz     1f

        lvx     v16,off96,r4
        lvx     v17,off96,r3
        VPERM(v16,v16,v16,byteswap)
        VPMSUMW(v16,v16,v17)
        vxor    v0,v0,v16

        /* Now xor all the parallel chunks together */
1:      vxor    v0,v0,v1
        vxor    v2,v2,v3
        vxor    v4,v4,v5
        vxor    v6,v6,v7

        vxor    v0,v0,v2
        vxor    v4,v4,v6

        vxor    v0,v0,v4

.Lbarrett_reduction:
        /* Barrett constants */
        LOAD_REG_ADDR(r3, .barrett_constants)

        lvx     const1,0,r3
        lvx     const2,off16,r3

        vsldoi  v1,v0,v0,8
        vxor    v0,v0,v1                /* xor two 64 bit results together */

#ifdef REFLECT
        /* shift left one bit */
        vspltisb v1,1
        vsl     v0,v0,v1
#endif

        vand    v0,v0,mask_64bit
#ifndef REFLECT
        /*
         * Now for the Barrett reduction algorithm. The idea is to calculate q,
         * the multiple of our polynomial that we need to subtract. By
         * doing the computation 2x bits higher (ie 64 bits) and shifting the
         * result back down 2x bits, we round down to the nearest multiple.
         */
        VPMSUMD(v1,v0,const1)   /* ma */
        vsldoi  v1,zeroes,v1,8  /* q = floor(ma/(2^64)) */
        VPMSUMD(v1,v1,const2)   /* qn */
        vxor    v0,v0,v1        /* a - qn, subtraction is xor in GF(2) */

        /*
         * Get the result into r3. We need to shift it left 8 bytes:
         * V0 [ 0 1 2 X ]
         * V0 [ 0 X 2 3 ]
         */
        vsldoi  v0,v0,zeroes,8  /* shift result into top 64 bits */
#else
        /*
         * The reflected version of Barrett reduction. Instead of bit
         * reflecting our data (which is expensive to do), we bit reflect our
         * constants and our algorithm, which means the intermediate data in
         * our vector registers goes from 0-63 instead of 63-0. We can reflect
         * the algorithm because we don't carry in mod 2 arithmetic.
         */
        vand    v1,v0,mask_32bit        /* bottom 32 bits of a */
        VPMSUMD(v1,v1,const1)           /* ma */
        vand    v1,v1,mask_32bit        /* bottom 32bits of ma */
        VPMSUMD(v1,v1,const2)           /* qn */
        vxor    v0,v0,v1                /* a - qn, subtraction is xor in GF(2) */

        /*
         * Since we are bit reflected, the result (ie the low 32 bits) is in
         * the high 32 bits. We just need to shift it left 4 bytes
         * V0 [ 0 1 X 3 ]
         * V0 [ 0 X 2 3 ]
         */
        vsldoi  v0,v0,zeroes,4          /* shift result into top 64 bits of */
#endif

        /* Get it into r3 */
        MFVRD(R3, v0)

.Lout:
        subi    r6,r1,56+10*16
        subi    r7,r1,56+2*16

        lvx     v20,0,r6
        lvx     v21,off16,r6
        lvx     v22,off32,r6
        lvx     v23,off48,r6
        lvx     v24,off64,r6
        lvx     v25,off80,r6
        lvx     v26,off96,r6
        lvx     v27,off112,r6
        lvx     v28,0,r7
        lvx     v29,off16,r7

        ld      r31,-8(r1)
        ld      r30,-16(r1)
        ld      r29,-24(r1)
        ld      r28,-32(r1)
        ld      r27,-40(r1)
        ld      r26,-48(r1)
        ld      r25,-56(r1)

        blr

.Lfirst_warm_up_done:
        lvx     const1,0,r3
        addi    r3,r3,16

        VPMSUMD(v8,v16,const1)
        VPMSUMD(v9,v17,const1)
        VPMSUMD(v10,v18,const1)
        VPMSUMD(v11,v19,const1)
        VPMSUMD(v12,v20,const1)
        VPMSUMD(v13,v21,const1)
        VPMSUMD(v14,v22,const1)
        VPMSUMD(v15,v23,const1)

        b       .Lsecond_cool_down

.Lshort:
        cmpdi   r5,0
        beq     .Lzero

        LOAD_REG_ADDR(r3, .short_constants)

        /* Calculate where in the constant table we need to start */
        subfic  r6,r5,256
        add     r3,r3,r6

        /* How many 16 byte chunks? */
        srdi    r7,r5,4
        mtctr   r7

        vxor    v19,v19,v19
        vxor    v20,v20,v20

        lvx     v0,0,r4
        lvx     v16,0,r3
        VPERM(v0,v0,v16,byteswap)
        vxor    v0,v0,v8        /* xor in initial value */
        VPMSUMW(v0,v0,v16)
        bdz     .Lv0

        lvx     v1,off16,r4
        lvx     v17,off16,r3
        VPERM(v1,v1,v17,byteswap)
        VPMSUMW(v1,v1,v17)
        bdz     .Lv1

        lvx     v2,off32,r4
        lvx     v16,off32,r3
        VPERM(v2,v2,v16,byteswap)
        VPMSUMW(v2,v2,v16)
        bdz     .Lv2

        lvx     v3,off48,r4
        lvx     v17,off48,r3
        VPERM(v3,v3,v17,byteswap)
        VPMSUMW(v3,v3,v17)
        bdz     .Lv3

        lvx     v4,off64,r4
        lvx     v16,off64,r3
        VPERM(v4,v4,v16,byteswap)
        VPMSUMW(v4,v4,v16)
        bdz     .Lv4

        lvx     v5,off80,r4
        lvx     v17,off80,r3
        VPERM(v5,v5,v17,byteswap)
        VPMSUMW(v5,v5,v17)
        bdz     .Lv5

        lvx     v6,off96,r4
        lvx     v16,off96,r3
        VPERM(v6,v6,v16,byteswap)
        VPMSUMW(v6,v6,v16)
        bdz     .Lv6

        lvx     v7,off112,r4
        lvx     v17,off112,r3
        VPERM(v7,v7,v17,byteswap)
        VPMSUMW(v7,v7,v17)
        bdz     .Lv7

        addi    r3,r3,128
        addi    r4,r4,128

        lvx     v8,0,r4
        lvx     v16,0,r3
        VPERM(v8,v8,v16,byteswap)
        VPMSUMW(v8,v8,v16)
        bdz     .Lv8

        lvx     v9,off16,r4
        lvx     v17,off16,r3
        VPERM(v9,v9,v17,byteswap)
        VPMSUMW(v9,v9,v17)
        bdz     .Lv9

        lvx     v10,off32,r4
        lvx     v16,off32,r3
        VPERM(v10,v10,v16,byteswap)
        VPMSUMW(v10,v10,v16)
        bdz     .Lv10

        lvx     v11,off48,r4
        lvx     v17,off48,r3
        VPERM(v11,v11,v17,byteswap)
        VPMSUMW(v11,v11,v17)
        bdz     .Lv11

        lvx     v12,off64,r4
        lvx     v16,off64,r3
        VPERM(v12,v12,v16,byteswap)
        VPMSUMW(v12,v12,v16)
        bdz     .Lv12

        lvx     v13,off80,r4
        lvx     v17,off80,r3
        VPERM(v13,v13,v17,byteswap)
        VPMSUMW(v13,v13,v17)
        bdz     .Lv13

        lvx     v14,off96,r4
        lvx     v16,off96,r3
        VPERM(v14,v14,v16,byteswap)
        VPMSUMW(v14,v14,v16)
        bdz     .Lv14

        lvx     v15,off112,r4
        lvx     v17,off112,r3
        VPERM(v15,v15,v17,byteswap)
        VPMSUMW(v15,v15,v17)

.Lv15:  vxor    v19,v19,v15
.Lv14:  vxor    v20,v20,v14
.Lv13:  vxor    v19,v19,v13
.Lv12:  vxor    v20,v20,v12
.Lv11:  vxor    v19,v19,v11
.Lv10:  vxor    v20,v20,v10
.Lv9:   vxor    v19,v19,v9
.Lv8:   vxor    v20,v20,v8
.Lv7:   vxor    v19,v19,v7
.Lv6:   vxor    v20,v20,v6
.Lv5:   vxor    v19,v19,v5
.Lv4:   vxor    v20,v20,v4
.Lv3:   vxor    v19,v19,v3
.Lv2:   vxor    v20,v20,v2
.Lv1:   vxor    v19,v19,v1
.Lv0:   vxor    v20,v20,v0

        vxor    v0,v19,v20

        b       .Lbarrett_reduction

.Lzero:
        mr      r3,r10
        b       .Lout

FUNC_END(CRC_FUNCTION_NAME)