lib/raid6/vpermxor.uc

   1 /*
   2  * Copyright 2017, Matt Brown, IBM Corp.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version
   7  * 2 of the License, or (at your option) any later version.
   8  *
   9  * vpermxor$#.c
  10  *
  11  * Based on H. Peter Anvin's paper - The mathematics of RAID-6
  12  *
  13  * $#-way unrolled portable integer math RAID-6 instruction set
  14  * This file is postprocessed using unroll.awk
  15  *
  16  * vpermxor$#.c makes use of the vpermxor instruction to optimise the RAID6 Q
  17  * syndrome calculations.
  18  * This can be run on systems which have both Altivec and vpermxor instruction.
  19  *
  20  * This instruction was introduced in POWER8 - ISA v2.07.
  21  */
  22
  23 #include <linux/raid/pq.h>
  24 #ifdef CONFIG_ALTIVEC
  25
  26 #include <altivec.h>
  27 #include <asm/ppc-opcode.h>
  28 #ifdef __KERNEL__
  29 #include <asm/cputable.h>
  30 #include <asm/switch_to.h>
  31 #endif
  32
  33 typedef vector unsigned char unative_t;
  34 #define NSIZE sizeof(unative_t)
  35
  36 static const vector unsigned char gf_low = {0x1e, 0x1c, 0x1a, 0x18, 0x16, 0x14,
  37                                             0x12, 0x10, 0x0e, 0x0c, 0x0a, 0x08,
  38                                             0x06, 0x04, 0x02,0x00};
  39 static const vector unsigned char gf_high = {0xfd, 0xdd, 0xbd, 0x9d, 0x7d, 0x5d,
  40                                              0x3d, 0x1d, 0xe0, 0xc0, 0xa0, 0x80,
  41                                              0x60, 0x40, 0x20, 0x00};
  42
  43 static void noinline raid6_vpermxor$#_gen_syndrome_real(int disks, size_t bytes,
  44                                                         void **ptrs)
  45 {
  46         u8 **dptr = (u8 **)ptrs;
  47         u8 *p, *q;
  48         int d, z, z0;
  49         unative_t wp$$, wq$$, wd$$;
  50
  51         z0 = disks - 3;         /* Highest data disk */
  52         p = dptr[z0+1];         /* XOR parity */
  53         q = dptr[z0+2];         /* RS syndrome */
  54
  55         for (d = 0; d < bytes; d += NSIZE*$#) {
  56                 wp$$ = wq$$ = *(unative_t *)&dptr[z0][d+$$*NSIZE];
  57
  58                 for (z = z0-1; z>=0; z--) {
  59                         wd$$ = *(unative_t *)&dptr[z][d+$$*NSIZE];
  60                         /* P syndrome */
  61                         wp$$ = vec_xor(wp$$, wd$$);
  62
  63                         /* Q syndrome */
  64                         asm(VPERMXOR(%0,%1,%2,%3):"=v"(wq$$):"v"(gf_high), "v"(gf_low), "v"(wq$$));
  65                         wq$$ = vec_xor(wq$$, wd$$);
  66                 }
  67                 *(unative_t *)&p[d+NSIZE*$$] = wp$$;
  68                 *(unative_t *)&q[d+NSIZE*$$] = wq$$;
  69         }
  70 }
  71
  72 static void raid6_vpermxor$#_gen_syndrome(int disks, size_t bytes, void **ptrs)
  73 {
  74         preempt_disable();
  75         enable_kernel_altivec();
  76
  77         raid6_vpermxor$#_gen_syndrome_real(disks, bytes, ptrs);
  78
  79         disable_kernel_altivec();
  80         preempt_enable();
  81 }
  82
  83 int raid6_have_altivec_vpermxor(void);
  84 #if $# == 1
  85 int raid6_have_altivec_vpermxor(void)
  86 {
  87         /* Check if arch has both altivec and the vpermxor instructions */
  88 # ifdef __KERNEL__
  89         return (cpu_has_feature(CPU_FTR_ALTIVEC_COMP) &&
  90                 cpu_has_feature(CPU_FTR_ARCH_207S));
  91 # else
  92         return 1;
  93 #endif
  94
  95 }
  96 #endif
  97
  98 const struct raid6_calls raid6_vpermxor$# = {
  99         raid6_vpermxor$#_gen_syndrome,
 100         NULL,
 101         raid6_have_altivec_vpermxor,
 102         "vpermxor$#",
 103         0
 104 };
 105 #endif