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+/*
+ * Hardware-accelerated CRC-32 variants for Linux on z Systems
+ *
+ * Use the z/Architecture Vector Extension Facility to accelerate the
+ * computing of CRC-32 checksums.
+ *
+ * This CRC-32 implementation algorithm processes the most-significant
+ * bit first (BE).
+ *
+ * Copyright IBM Corp. 2015
+ * Author(s): Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
+ */
+
+#include <linux/linkage.h>
+#include <asm/vx-insn.h>
+
+/* Vector register range containing CRC-32 constants */
+#define CONST_R1R2 %v9
+#define CONST_R3R4 %v10
+#define CONST_R5 %v11
+#define CONST_R6 %v12
+#define CONST_RU_POLY %v13
+#define CONST_CRC_POLY %v14
+
+.data
+.align 8
+
+/*
+ * The CRC-32 constant block contains reduction constants to fold and
+ * process particular chunks of the input data stream in parallel.
+ *
+ * For the CRC-32 variants, the constants are precomputed according to
+ * these defintions:
+ *
+ * R1 = x4*128+64 mod P(x)
+ * R2 = x4*128 mod P(x)
+ * R3 = x128+64 mod P(x)
+ * R4 = x128 mod P(x)
+ * R5 = x96 mod P(x)
+ * R6 = x64 mod P(x)
+ *
+ * Barret reduction constant, u, is defined as floor(x**64 / P(x)).
+ *
+ * where P(x) is the polynomial in the normal domain and the P'(x) is the
+ * polynomial in the reversed (bitreflected) domain.
+ *
+ * Note that the constant definitions below are extended in order to compute
+ * intermediate results with a single VECTOR GALOIS FIELD MULTIPLY instruction.
+ * The righmost doubleword can be 0 to prevent contribution to the result or
+ * can be multiplied by 1 to perform an XOR without the need for a separate
+ * VECTOR EXCLUSIVE OR instruction.
+ *
+ * CRC-32 (IEEE 802.3 Ethernet, ...) polynomials:
+ *
+ * P(x) = 0x04C11DB7
+ * P'(x) = 0xEDB88320
+ */
+
+.Lconstants_CRC_32_BE:
+ .quad 0x08833794c, 0x0e6228b11 # R1, R2
+ .quad 0x0c5b9cd4c, 0x0e8a45605 # R3, R4
+ .quad 0x0f200aa66, 1 << 32 # R5, x32
+ .quad 0x0490d678d, 1 # R6, 1
+ .quad 0x104d101df, 0 # u
+ .quad 0x104C11DB7, 0 # P(x)
+
+.previous
+
+.text
+/*
+ * The CRC-32 function(s) use these calling conventions:
+ *
+ * Parameters:
+ *
+ * %r2: Initial CRC value, typically ~0; and final CRC (return) value.
+ * %r3: Input buffer pointer, performance might be improved if the
+ * buffer is on a doubleword boundary.
+ * %r4: Length of the buffer, must be 64 bytes or greater.
+ *
+ * Register usage:
+ *
+ * %r5: CRC-32 constant pool base pointer.
+ * V0: Initial CRC value and intermediate constants and results.
+ * V1..V4: Data for CRC computation.
+ * V5..V8: Next data chunks that are fetched from the input buffer.
+ *
+ * V9..V14: CRC-32 constants.
+ */
+ENTRY(crc32_be_vgfm_16)
+ /* Load CRC-32 constants */
+ larl %r5,.Lconstants_CRC_32_BE
+ VLM CONST_R1R2,CONST_CRC_POLY,0,%r5
+
+ /* Load the initial CRC value into the leftmost word of V0. */
+ VZERO %v0
+ VLVGF %v0,%r2,0
+
+ /* Load a 64-byte data chunk and XOR with CRC */
+ VLM %v1,%v4,0,%r3 /* 64-bytes into V1..V4 */
+ VX %v1,%v0,%v1 /* V1 ^= CRC */
+ aghi %r3,64 /* BUF = BUF + 64 */
+ aghi %r4,-64 /* LEN = LEN - 64 */
+
+ /* Check remaining buffer size and jump to proper folding method */
+ cghi %r4,64
+ jl .Lless_than_64bytes
+
+.Lfold_64bytes_loop:
+ /* Load the next 64-byte data chunk into V5 to V8 */
+ VLM %v5,%v8,0,%r3
+
+ /*
+ * Perform a GF(2) multiplication of the doublewords in V1 with
+ * the reduction constants in V0. The intermediate result is
+ * then folded (accumulated) with the next data chunk in V5 and
+ * stored in V1. Repeat this step for the register contents
+ * in V2, V3, and V4 respectively.
+ */
+ VGFMAG %v1,CONST_R1R2,%v1,%v5
+ VGFMAG %v2,CONST_R1R2,%v2,%v6
+ VGFMAG %v3,CONST_R1R2,%v3,%v7
+ VGFMAG %v4,CONST_R1R2,%v4,%v8
+
+ /* Adjust buffer pointer and length for next loop */
+ aghi %r3,64 /* BUF = BUF + 64 */
+ aghi %r4,-64 /* LEN = LEN - 64 */
+
+ cghi %r4,64
+ jnl .Lfold_64bytes_loop
+
+.Lless_than_64bytes:
+ /* Fold V1 to V4 into a single 128-bit value in V1 */
+ VGFMAG %v1,CONST_R3R4,%v1,%v2
+ VGFMAG %v1,CONST_R3R4,%v1,%v3
+ VGFMAG %v1,CONST_R3R4,%v1,%v4
+
+ /* Check whether to continue with 64-bit folding */
+ cghi %r4,16
+ jl .Lfinal_fold
+
+.Lfold_16bytes_loop:
+
+ VL %v2,0,,%r3 /* Load next data chunk */
+ VGFMAG %v1,CONST_R3R4,%v1,%v2 /* Fold next data chunk */
+
+ /* Adjust buffer pointer and size for folding next data chunk */
+ aghi %r3,16
+ aghi %r4,-16
+
+ /* Process remaining data chunks */
+ cghi %r4,16
+ jnl .Lfold_16bytes_loop
+
+.Lfinal_fold:
+ /*
+ * The R5 constant is used to fold a 128-bit value into an 96-bit value
+ * that is XORed with the next 96-bit input data chunk. To use a single
+ * VGFMG instruction, multiply the rightmost 64-bit with x^32 (1<<32) to
+ * form an intermediate 96-bit value (with appended zeros) which is then
+ * XORed with the intermediate reduction result.
+ */
+ VGFMG %v1,CONST_R5,%v1
+
+ /*
+ * Further reduce the remaining 96-bit value to a 64-bit value using a
+ * single VGFMG, the rightmost doubleword is multiplied with 0x1. The
+ * intermediate result is then XORed with the product of the leftmost
+ * doubleword with R6. The result is a 64-bit value and is subject to
+ * the Barret reduction.
+ */
+ VGFMG %v1,CONST_R6,%v1
+
+ /*
+ * The input values to the Barret reduction are the degree-63 polynomial
+ * in V1 (R(x)), degree-32 generator polynomial, and the reduction
+ * constant u. The Barret reduction result is the CRC value of R(x) mod
+ * P(x).
+ *
+ * The Barret reduction algorithm is defined as:
+ *
+ * 1. T1(x) = floor( R(x) / x^32 ) GF2MUL u
+ * 2. T2(x) = floor( T1(x) / x^32 ) GF2MUL P(x)
+ * 3. C(x) = R(x) XOR T2(x) mod x^32
+ *
+ * Note: To compensate the division by x^32, use the vector unpack
+ * instruction to move the leftmost word into the leftmost doubleword
+ * of the vector register. The rightmost doubleword is multiplied
+ * with zero to not contribute to the intermedate results.
+ */
+
+ /* T1(x) = floor( R(x) / x^32 ) GF2MUL u */
+ VUPLLF %v2,%v1
+ VGFMG %v2,CONST_RU_POLY,%v2
+
+ /*
+ * Compute the GF(2) product of the CRC polynomial in VO with T1(x) in
+ * V2 and XOR the intermediate result, T2(x), with the value in V1.
+ * The final result is in the rightmost word of V2.
+ */
+ VUPLLF %v2,%v2
+ VGFMAG %v2,CONST_CRC_POLY,%v2,%v1
+
+.Ldone:
+ VLGVF %r2,%v2,3
+ br %r14
+
+.previous