diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/flash/nand_ecc_kw.c | 348 |
1 files changed, 174 insertions, 174 deletions
diff --git a/src/flash/nand_ecc_kw.c b/src/flash/nand_ecc_kw.c index ecc7adc2..a7fae626 100644 --- a/src/flash/nand_ecc_kw.c +++ b/src/flash/nand_ecc_kw.c @@ -1,174 +1,174 @@ -/*
- * Reed-Solomon ECC handling for the Marvell Kirkwood SOC
- * Copyright (C) 2009 Marvell Semiconductor, Inc.
- *
- * Authors: Lennert Buytenhek <buytenh@wantstofly.org>
- * Nicolas Pitre <nico@cam.org>
- *
- * This file is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License as published by the
- * Free Software Foundation; either version 2 or (at your option) any
- * later version.
- *
- * This file is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
- * for more details.
- */
-
-#ifdef HAVE_CONFIG_H
-#include "config.h"
-#endif
-
-#include <sys/types.h>
-#include "nand.h"
-
-
-/*****************************************************************************
- * Arithmetic in GF(2^10) ("F") modulo x^10 + x^3 + 1.
- *
- * For multiplication, a discrete log/exponent table is used, with
- * primitive element x (F is a primitive field, so x is primitive).
- */
-#define MODPOLY 0x409 /* x^10 + x^3 + 1 in binary */
-
-/*
- * Maps an integer a [0..1022] to a polynomial b = gf_exp[a] in
- * GF(2^10) mod x^10 + x^3 + 1 such that b = x ^ a. There's two
- * identical copies of this array back-to-back so that we can save
- * the mod 1023 operation when doing a GF multiplication.
- */
-static uint16_t gf_exp[1023 + 1023];
-
-/*
- * Maps a polynomial b in GF(2^10) mod x^10 + x^3 + 1 to an index
- * a = gf_log[b] in [0..1022] such that b = x ^ a.
- */
-static uint16_t gf_log[1024];
-
-static void gf_build_log_exp_table(void)
-{
- int i;
- int p_i;
-
- /*
- * p_i = x ^ i
- *
- * Initialise to 1 for i = 0.
- */
- p_i = 1;
-
- for (i = 0; i < 1023; i++) {
- gf_exp[i] = p_i;
- gf_exp[i + 1023] = p_i;
- gf_log[p_i] = i;
-
- /*
- * p_i = p_i * x
- */
- p_i <<= 1;
- if (p_i & (1 << 10))
- p_i ^= MODPOLY;
- }
-}
-
-
-/*****************************************************************************
- * Reed-Solomon code
- *
- * This implements a (1023,1015) Reed-Solomon ECC code over GF(2^10)
- * mod x^10 + x^3 + 1, shortened to (520,512). The ECC data consists
- * of 8 10-bit symbols, or 10 8-bit bytes.
- *
- * Given 512 bytes of data, computes 10 bytes of ECC.
- *
- * This is done by converting the 512 bytes to 512 10-bit symbols
- * (elements of F), interpreting those symbols as a polynomial in F[X]
- * by taking symbol 0 as the coefficient of X^8 and symbol 511 as the
- * coefficient of X^519, and calculating the residue of that polynomial
- * divided by the generator polynomial, which gives us the 8 ECC symbols
- * as the remainder. Finally, we convert the 8 10-bit ECC symbols to 10
- * 8-bit bytes.
- *
- * The generator polynomial is hardcoded, as that is faster, but it
- * can be computed by taking the primitive element a = x (in F), and
- * constructing a polynomial in F[X] with roots a, a^2, a^3, ..., a^8
- * by multiplying the minimal polynomials for those roots (which are
- * just 'x - a^i' for each i).
- *
- * Note: due to unfortunate circumstances, the bootrom in the Kirkwood SOC
- * expects the ECC to be computed backward, i.e. from the last byte down
- * to the first one.
- */
-int nand_calculate_ecc_kw(struct nand_device_s *device, const u8 *data, u8 *ecc)
-{
- unsigned int r7, r6, r5, r4, r3, r2, r1, r0;
- int i;
- static int tables_initialized = 0;
-
- if (!tables_initialized) {
- gf_build_log_exp_table();
- tables_initialized = 1;
- }
-
- /*
- * Load bytes 504..511 of the data into r.
- */
- r0 = data[504];
- r1 = data[505];
- r2 = data[506];
- r3 = data[507];
- r4 = data[508];
- r5 = data[509];
- r6 = data[510];
- r7 = data[511];
-
-
- /*
- * Shift bytes 503..0 (in that order) into r0, followed
- * by eight zero bytes, while reducing the polynomial by the
- * generator polynomial in every step.
- */
- for (i = 503; i >= -8; i--) {
- unsigned int d;
-
- d = 0;
- if (i >= 0)
- d = data[i];
-
- if (r7) {
- u16 *t = gf_exp + gf_log[r7];
-
- r7 = r6 ^ t[0x21c];
- r6 = r5 ^ t[0x181];
- r5 = r4 ^ t[0x18e];
- r4 = r3 ^ t[0x25f];
- r3 = r2 ^ t[0x197];
- r2 = r1 ^ t[0x193];
- r1 = r0 ^ t[0x237];
- r0 = d ^ t[0x024];
- } else {
- r7 = r6;
- r6 = r5;
- r5 = r4;
- r4 = r3;
- r3 = r2;
- r2 = r1;
- r1 = r0;
- r0 = d;
- }
- }
-
- ecc[0] = r0;
- ecc[1] = (r0 >> 8) | (r1 << 2);
- ecc[2] = (r1 >> 6) | (r2 << 4);
- ecc[3] = (r2 >> 4) | (r3 << 6);
- ecc[4] = (r3 >> 2);
- ecc[5] = r4;
- ecc[6] = (r4 >> 8) | (r5 << 2);
- ecc[7] = (r5 >> 6) | (r6 << 4);
- ecc[8] = (r6 >> 4) | (r7 << 6);
- ecc[9] = (r7 >> 2);
-
- return 0;
-}
+/* + * Reed-Solomon ECC handling for the Marvell Kirkwood SOC + * Copyright (C) 2009 Marvell Semiconductor, Inc. + * + * Authors: Lennert Buytenhek <buytenh@wantstofly.org> + * Nicolas Pitre <nico@cam.org> + * + * This file is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; either version 2 or (at your option) any + * later version. + * + * This file is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * for more details. + */ + +#ifdef HAVE_CONFIG_H +#include "config.h" +#endif + +#include <sys/types.h> +#include "nand.h" + + +/***************************************************************************** + * Arithmetic in GF(2^10) ("F") modulo x^10 + x^3 + 1. + * + * For multiplication, a discrete log/exponent table is used, with + * primitive element x (F is a primitive field, so x is primitive). + */ +#define MODPOLY 0x409 /* x^10 + x^3 + 1 in binary */ + +/* + * Maps an integer a [0..1022] to a polynomial b = gf_exp[a] in + * GF(2^10) mod x^10 + x^3 + 1 such that b = x ^ a. There's two + * identical copies of this array back-to-back so that we can save + * the mod 1023 operation when doing a GF multiplication. + */ +static uint16_t gf_exp[1023 + 1023]; + +/* + * Maps a polynomial b in GF(2^10) mod x^10 + x^3 + 1 to an index + * a = gf_log[b] in [0..1022] such that b = x ^ a. + */ +static uint16_t gf_log[1024]; + +static void gf_build_log_exp_table(void) +{ + int i; + int p_i; + + /* + * p_i = x ^ i + * + * Initialise to 1 for i = 0. + */ + p_i = 1; + + for (i = 0; i < 1023; i++) { + gf_exp[i] = p_i; + gf_exp[i + 1023] = p_i; + gf_log[p_i] = i; + + /* + * p_i = p_i * x + */ + p_i <<= 1; + if (p_i & (1 << 10)) + p_i ^= MODPOLY; + } +} + + +/***************************************************************************** + * Reed-Solomon code + * + * This implements a (1023,1015) Reed-Solomon ECC code over GF(2^10) + * mod x^10 + x^3 + 1, shortened to (520,512). The ECC data consists + * of 8 10-bit symbols, or 10 8-bit bytes. + * + * Given 512 bytes of data, computes 10 bytes of ECC. + * + * This is done by converting the 512 bytes to 512 10-bit symbols + * (elements of F), interpreting those symbols as a polynomial in F[X] + * by taking symbol 0 as the coefficient of X^8 and symbol 511 as the + * coefficient of X^519, and calculating the residue of that polynomial + * divided by the generator polynomial, which gives us the 8 ECC symbols + * as the remainder. Finally, we convert the 8 10-bit ECC symbols to 10 + * 8-bit bytes. + * + * The generator polynomial is hardcoded, as that is faster, but it + * can be computed by taking the primitive element a = x (in F), and + * constructing a polynomial in F[X] with roots a, a^2, a^3, ..., a^8 + * by multiplying the minimal polynomials for those roots (which are + * just 'x - a^i' for each i). + * + * Note: due to unfortunate circumstances, the bootrom in the Kirkwood SOC + * expects the ECC to be computed backward, i.e. from the last byte down + * to the first one. + */ +int nand_calculate_ecc_kw(struct nand_device_s *device, const u8 *data, u8 *ecc) +{ + unsigned int r7, r6, r5, r4, r3, r2, r1, r0; + int i; + static int tables_initialized = 0; + + if (!tables_initialized) { + gf_build_log_exp_table(); + tables_initialized = 1; + } + + /* + * Load bytes 504..511 of the data into r. + */ + r0 = data[504]; + r1 = data[505]; + r2 = data[506]; + r3 = data[507]; + r4 = data[508]; + r5 = data[509]; + r6 = data[510]; + r7 = data[511]; + + + /* + * Shift bytes 503..0 (in that order) into r0, followed + * by eight zero bytes, while reducing the polynomial by the + * generator polynomial in every step. + */ + for (i = 503; i >= -8; i--) { + unsigned int d; + + d = 0; + if (i >= 0) + d = data[i]; + + if (r7) { + u16 *t = gf_exp + gf_log[r7]; + + r7 = r6 ^ t[0x21c]; + r6 = r5 ^ t[0x181]; + r5 = r4 ^ t[0x18e]; + r4 = r3 ^ t[0x25f]; + r3 = r2 ^ t[0x197]; + r2 = r1 ^ t[0x193]; + r1 = r0 ^ t[0x237]; + r0 = d ^ t[0x024]; + } else { + r7 = r6; + r6 = r5; + r5 = r4; + r4 = r3; + r3 = r2; + r2 = r1; + r1 = r0; + r0 = d; + } + } + + ecc[0] = r0; + ecc[1] = (r0 >> 8) | (r1 << 2); + ecc[2] = (r1 >> 6) | (r2 << 4); + ecc[3] = (r2 >> 4) | (r3 << 6); + ecc[4] = (r3 >> 2); + ecc[5] = r4; + ecc[6] = (r4 >> 8) | (r5 << 2); + ecc[7] = (r5 >> 6) | (r6 << 4); + ecc[8] = (r6 >> 4) | (r7 << 6); + ecc[9] = (r7 >> 2); + + return 0; +} |