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Commit b5dceda1 authored by Anup Patel's avatar Anup Patel Committed by Vinod Koul
Browse files

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



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: default avatarAnup Patel <anup.patel@broadcom.com>
Reviewed-by: default avatarScott Branden <scott.branden@broadcom.com>
Reviewed-by: default avatarRay Jui <ray.jui@broadcom.com>
Acked-by: default avatarShaohua Li <shli@fb.com>
Signed-off-by: default avatarVinod Koul <vinod.koul@intel.com>
parent 2ea659a9

include/linux/raid/pq.h

+1 −0
Original line number Diff line number Diff line
@@ -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)));

lib/raid6/mktables.c

+20 −0
Original line number Diff line number Diff line
@@ -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");