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lib/raid6: Add log-of-2 table for RAID6 HW requiring disk position

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The raid6_gfexp table represents {2}^n values for 0 <= n < 256. The
Linux async_tx framework pass values from raid6_gfexp as coefficients
for each source to prep_dma_pq() callback of DMA channel with PQ
capability. This creates problem for RAID6 offload engines (such as
Broadcom SBA) which take disk position (i.e. log of {2}) instead of
multiplicative cofficients from raid6_gfexp table.

This patch adds raid6_gflog table having log-of-2 value for any given
x such that 0 <= x < 256. For any given disk coefficient x, the
corresponding disk position is given by raid6_gflog[x]. The RAID6
offload engine driver can use this newly added raid6_gflog table to
get disk position from multiplicative coefficient.

Signed-off-by: Anup Patel <anup.patel@broadcom.com>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>
Reviewed-by: Ray Jui <ray.jui@broadcom.com>
Acked-by: Shaohua Li <shli@fb.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
This commit is contained in:
Anup Patel 2017-05-15 10:34:52 +05:30 committed by Vinod Koul
parent 2ea659a9ef
commit b5dceda1f7
2 changed files with 21 additions and 0 deletions
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1
include/linux/raid/pq.h
View File

@ -142,6 +142,7 @@ int raid6_select_algo(void);
extern const u8 raid6_gfmul[256][256] __attribute__((aligned(256)));
extern const u8 raid6_vgfmul[256][32] __attribute__((aligned(256)));
extern const u8 raid6_gfexp[256] __attribute__((aligned(256)));
extern const u8 raid6_gflog[256] __attribute__((aligned(256)));
extern const u8 raid6_gfinv[256] __attribute__((aligned(256)));
extern const u8 raid6_gfexi[256] __attribute__((aligned(256)));

20
lib/raid6/mktables.c
View File

@ -125,6 +125,26 @@ int main(int argc, char *argv[])
printf("EXPORT_SYMBOL(raid6_gfexp);\n");
printf("#endif\n");
/* Compute log-of-2 table */
printf("\nconst u8 __attribute__((aligned(256)))\n"
"raid6_gflog[256] =\n" "{\n");
for (i = 0; i < 256; i += 8) {
printf("\t");
for (j = 0; j < 8; j++) {
v = 255;
for (k = 0; k < 256; k++)
if (exptbl[k] == (i + j)) {
v = k;
break;
}
printf("0x%02x,%c", v, (j == 7) ? '\n' : ' ');
}
}
printf("};\n");
printf("#ifdef __KERNEL__\n");
printf("EXPORT_SYMBOL(raid6_gflog);\n");
printf("#endif\n");
/* Compute inverse table x^-1 == x^254 */
printf("\nconst u8 __attribute__((aligned(256)))\n"
"raid6_gfinv[256] =\n" "{\n");