Add a tool to generate raw NAND images

Generating raw NAND images is particularly useful for boot0 images
creation since the mainline driver is not supporting the funky layout
used by Allwinner's ROM code to load the boot0 binary from NAND.

This tools also allows one to generate raw images for 'normal' partitions
so that they can be flashed before soldering on the NAND on the board
(using a regular NAND programmer).

The tool takes care of generating ECC bytes and randomizing data as
expected by the NAND controller, and re-arranging the ECC/data sections
correctly.
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

Makefile

@@ -41,7 +41,7 @@ FEXC_LINKS = bin2fex fex2bin
 # Tools which are only useful on the target
 TARGET_TOOLS = sunxi-pio
 
-MISC_TOOLS = phoenix_info
+MISC_TOOLS = phoenix_info sunxi-nand-image-builder
 
 # ARM binaries and images
 # Note: To use this target, set/adjust CROSS_COMPILE and MKSUNXIBOOT if needed

README.md

@@ -46,6 +46,9 @@ Manipulate PIO register dumps
 ### sunxi-nand-part
 Tool for manipulating Allwinner NAND partition tables
 
+### sunxi-nand-image-builder
+Tool used to create raw NAND images (including boot0 images)
+
 ### jtag-loop.sunxi
 ARM native boot helper to force the SD port into JTAG and then stop,
 to ease debugging of bootloaders.

nand-image-builder.c

+/*
+ * Generic binary BCH encoding/decoding library
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program 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.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 51
+ * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Copyright © 2011 Parrot S.A.
+ *
+ * Author: Ivan Djelic <ivan.djelic@parrot.com>
+ *
+ * Description:
+ *
+ * This library provides runtime configurable encoding/decoding of binary
+ * Bose-Chaudhuri-Hocquenghem (BCH) codes.
+ *
+ * Call init_bch to get a pointer to a newly allocated bch_control structure for
+ * the given m (Galois field order), t (error correction capability) and
+ * (optional) primitive polynomial parameters.
+ *
+ * Call encode_bch to compute and store ecc parity bytes to a given buffer.
+ * Call decode_bch to detect and locate errors in received data.
+ *
+ * On systems supporting hw BCH features, intermediate results may be provided
+ * to decode_bch in order to skip certain steps. See decode_bch() documentation
+ * for details.
+ *
+ * Option CONFIG_BCH_CONST_PARAMS can be used to force fixed values of
+ * parameters m and t; thus allowing extra compiler optimizations and providing
+ * better (up to 2x) encoding performance. Using this option makes sense when
+ * (m,t) are fixed and known in advance, e.g. when using BCH error correction
+ * on a particular NAND flash device.
+ *
+ * Algorithmic details:
+ *
+ * Encoding is performed by processing 32 input bits in parallel, using 4
+ * remainder lookup tables.
+ *
+ * The final stage of decoding involves the following internal steps:
+ * a. Syndrome computation
+ * b. Error locator polynomial computation using Berlekamp-Massey algorithm
+ * c. Error locator root finding (by far the most expensive step)
+ *
+ * In this implementation, step c is not performed using the usual Chien search.
+ * Instead, an alternative approach described in [1] is used. It consists in
+ * factoring the error locator polynomial using the Berlekamp Trace algorithm
+ * (BTA) down to a certain degree (4), after which ad hoc low-degree polynomial
+ * solving techniques [2] are used. The resulting algorithm, called BTZ, yields
+ * much better performance than Chien search for usual (m,t) values (typically
+ * m >= 13, t < 32, see [1]).
+ *
+ * [1] B. Biswas, V. Herbert. Efficient root finding of polynomials over fields
+ * of characteristic 2, in: Western European Workshop on Research in Cryptology
+ * - WEWoRC 2009, Graz, Austria, LNCS, Springer, July 2009, to appear.
+ * [2] [Zin96] V.A. Zinoviev. On the solution of equations of degree 10 over
+ * finite fields GF(2^q). In Rapport de recherche INRIA no 2829, 1996.
+ */
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <errno.h>
+#include <getopt.h>
+
+#include "portable_endian.h"
+
+#if defined(CONFIG_BCH_CONST_PARAMS)
+#define GF_M(_p)               (CONFIG_BCH_CONST_M)
+#define GF_T(_p)               (CONFIG_BCH_CONST_T)
+#define GF_N(_p)               ((1 << (CONFIG_BCH_CONST_M))-1)
+#else
+#define GF_M(_p)               ((_p)->m)
+#define GF_T(_p)               ((_p)->t)
+#define GF_N(_p)               ((_p)->n)
+#endif
+
+#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
+
+#define BCH_ECC_WORDS(_p)      DIV_ROUND_UP(GF_M(_p)*GF_T(_p), 32)
+#define BCH_ECC_BYTES(_p)      DIV_ROUND_UP(GF_M(_p)*GF_T(_p), 8)
+
+#ifndef dbg
+#define dbg(_fmt, args...)     do {} while (0)
+#endif
+
+#define cpu_to_be32 htobe32
+#define kfree free
+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
+
+#define BCH_PRIMITIVE_POLY	0x5803
+
+struct image_info {
+	int ecc_strength;
+	int ecc_step_size;
+	int page_size;
+	int oob_size;
+	int usable_page_size;
+	int eraseblock_size;
+	int scramble;
+	int boot0;
+	off_t offset;
+	const char *source;
+	const char *dest;
+};
+
+/**
+ * struct bch_control - BCH control structure
+ * @m:          Galois field order
+ * @n:          maximum codeword size in bits (= 2^m-1)
+ * @t:          error correction capability in bits
+ * @ecc_bits:   ecc exact size in bits, i.e. generator polynomial degree (<=m*t)
+ * @ecc_bytes:  ecc max size (m*t bits) in bytes
+ * @a_pow_tab:  Galois field GF(2^m) exponentiation lookup table
+ * @a_log_tab:  Galois field GF(2^m) log lookup table
+ * @mod8_tab:   remainder generator polynomial lookup tables
+ * @ecc_buf:    ecc parity words buffer
+ * @ecc_buf2:   ecc parity words buffer
+ * @xi_tab:     GF(2^m) base for solving degree 2 polynomial roots
+ * @syn:        syndrome buffer
+ * @cache:      log-based polynomial representation buffer
+ * @elp:        error locator polynomial
+ * @poly_2t:    temporary polynomials of degree 2t
+ */
+struct bch_control {
+	unsigned int    m;
+	unsigned int    n;
+	unsigned int    t;
+	unsigned int    ecc_bits;
+	unsigned int    ecc_bytes;
+/* private: */
+	uint16_t       *a_pow_tab;
+	uint16_t       *a_log_tab;
+	uint32_t       *mod8_tab;
+	uint32_t       *ecc_buf;
+	uint32_t       *ecc_buf2;
+	unsigned int   *xi_tab;
+	unsigned int   *syn;
+	int            *cache;
+	struct gf_poly *elp;
+	struct gf_poly *poly_2t[4];
+};
+
+static int fls(int x)
+{
+	int r = 32;
+
+	if (!x)
+		return 0;
+	if (!(x & 0xffff0000u)) {
+		x <<= 16;
+		r -= 16;
+	}
+	if (!(x & 0xff000000u)) {
+		x <<= 8;
+		r -= 8;
+	}
+	if (!(x & 0xf0000000u)) {
+		x <<= 4;
+		r -= 4;
+	}
+	if (!(x & 0xc0000000u)) {
+		x <<= 2;
+		r -= 2;
+	}
+	if (!(x & 0x80000000u)) {
+		x <<= 1;
+		r -= 1;
+	}
+	return r;
+}
+
+/*
+ * represent a polynomial over GF(2^m)
+ */
+struct gf_poly {
+	unsigned int deg;    /* polynomial degree */
+	unsigned int c[0];   /* polynomial terms */
+};
+
+/* given its degree, compute a polynomial size in bytes */
+#define GF_POLY_SZ(_d) (sizeof(struct gf_poly)+((_d)+1)*sizeof(unsigned int))
+
+/* polynomial of degree 1 */
+struct gf_poly_deg1 {
+	struct gf_poly poly;
+	unsigned int   c[2];
+};
+
+/*
+ * same as encode_bch(), but process input data one byte at a time
+ */
+static void encode_bch_unaligned(struct bch_control *bch,
+				 const unsigned char *data, unsigned int len,
+				 uint32_t *ecc)
+{
+	int i;
+	const uint32_t *p;
+	const int l = BCH_ECC_WORDS(bch)-1;
+
+	while (len--) {
+		p = bch->mod8_tab + (l+1)*(((ecc[0] >> 24)^(*data++)) & 0xff);
+
+		for (i = 0; i < l; i++)
+			ecc[i] = ((ecc[i] << 8)|(ecc[i+1] >> 24))^(*p++);
+
+		ecc[l] = (ecc[l] << 8)^(*p);
+	}
+}
+
+/*
+ * convert ecc bytes to aligned, zero-padded 32-bit ecc words
+ */
+static void load_ecc8(struct bch_control *bch, uint32_t *dst,
+		      const uint8_t *src)
+{
+	uint8_t pad[4] = {0, 0, 0, 0};
+	unsigned int i, nwords = BCH_ECC_WORDS(bch)-1;
+
+	for (i = 0; i < nwords; i++, src += 4)
+		dst[i] = (src[0] << 24)|(src[1] << 16)|(src[2] << 8)|src[3];
+
+	memcpy(pad, src, BCH_ECC_BYTES(bch)-4*nwords);
+	dst[nwords] = (pad[0] << 24)|(pad[1] << 16)|(pad[2] << 8)|pad[3];
+}
+
+/*
+ * convert 32-bit ecc words to ecc bytes
+ */
+static void store_ecc8(struct bch_control *bch, uint8_t *dst,
+		       const uint32_t *src)
+{
+	uint8_t pad[4];
+	unsigned int i, nwords = BCH_ECC_WORDS(bch)-1;
+
+	for (i = 0; i < nwords; i++) {
+		*dst++ = (src[i] >> 24);
+		*dst++ = (src[i] >> 16) & 0xff;
+		*dst++ = (src[i] >>  8) & 0xff;
+		*dst++ = (src[i] >>  0) & 0xff;
+	}
+	pad[0] = (src[nwords] >> 24);
+	pad[1] = (src[nwords] >> 16) & 0xff;
+	pad[2] = (src[nwords] >>  8) & 0xff;
+	pad[3] = (src[nwords] >>  0) & 0xff;
+	memcpy(dst, pad, BCH_ECC_BYTES(bch)-4*nwords);
+}
+
+/**
+ * encode_bch - calculate BCH ecc parity of data
+ * @bch:   BCH control structure
+ * @data:  data to encode
+ * @len:   data length in bytes
+ * @ecc:   ecc parity data, must be initialized by caller
+ *
+ * The @ecc parity array is used both as input and output parameter, in order to
+ * allow incremental computations. It should be of the size indicated by member
+ * @ecc_bytes of @bch, and should be initialized to 0 before the first call.
+ *
+ * The exact number of computed ecc parity bits is given by member @ecc_bits of
+ * @bch; it may be less than m*t for large values of t.
+ */
+static void encode_bch(struct bch_control *bch, const uint8_t *data,
+		unsigned int len, uint8_t *ecc)
+{
+	const unsigned int l = BCH_ECC_WORDS(bch)-1;
+	unsigned int i, mlen;
+	unsigned long m;
+	uint32_t w, r[l+1];
+	const uint32_t * const tab0 = bch->mod8_tab;
+	const uint32_t * const tab1 = tab0 + 256*(l+1);
+	const uint32_t * const tab2 = tab1 + 256*(l+1);
+	const uint32_t * const tab3 = tab2 + 256*(l+1);
+	const uint32_t *pdata, *p0, *p1, *p2, *p3;
+
+	if (ecc) {
+		/* load ecc parity bytes into internal 32-bit buffer */
+		load_ecc8(bch, bch->ecc_buf, ecc);
+	} else {
+		memset(bch->ecc_buf, 0, sizeof(r));
+	}
+
+	/* process first unaligned data bytes */
+	m = ((unsigned long)data) & 3;
+	if (m) {
+		mlen = (len < (4-m)) ? len : 4-m;
+		encode_bch_unaligned(bch, data, mlen, bch->ecc_buf);
+		data += mlen;
+		len  -= mlen;
+	}
+
+	/* process 32-bit aligned data words */
+	pdata = (uint32_t *)data;
+	mlen  = len/4;
+	data += 4*mlen;
+	len  -= 4*mlen;
+	memcpy(r, bch->ecc_buf, sizeof(r));
+
+	/*
+	 * split each 32-bit word into 4 polynomials of weight 8 as follows:
+	 *
+	 * 31 ...24  23 ...16  15 ... 8  7 ... 0
+	 * xxxxxxxx  yyyyyyyy  zzzzzzzz  tttttttt
+	 *                               tttttttt  mod g = r0 (precomputed)
+	 *                     zzzzzzzz  00000000  mod g = r1 (precomputed)
+	 *           yyyyyyyy  00000000  00000000  mod g = r2 (precomputed)
+	 * xxxxxxxx  00000000  00000000  00000000  mod g = r3 (precomputed)
+	 * xxxxxxxx  yyyyyyyy  zzzzzzzz  tttttttt  mod g = r0^r1^r2^r3
+	 */
+	while (mlen--) {
+		/* input data is read in big-endian format */
+		w = r[0]^cpu_to_be32(*pdata++);
+		p0 = tab0 + (l+1)*((w >>  0) & 0xff);
+		p1 = tab1 + (l+1)*((w >>  8) & 0xff);
+		p2 = tab2 + (l+1)*((w >> 16) & 0xff);
+		p3 = tab3 + (l+1)*((w >> 24) & 0xff);
+
+		for (i = 0; i < l; i++)
+			r[i] = r[i+1]^p0[i]^p1[i]^p2[i]^p3[i];
+
+		r[l] = p0[l]^p1[l]^p2[l]^p3[l];
+	}
+	memcpy(bch->ecc_buf, r, sizeof(r));
+
+	/* process last unaligned bytes */
+	if (len)
+		encode_bch_unaligned(bch, data, len, bch->ecc_buf);
+
+	/* store ecc parity bytes into original parity buffer */
+	if (ecc)
+		store_ecc8(bch, ecc, bch->ecc_buf);
+}
+
+static inline int modulo(struct bch_control *bch, unsigned int v)
+{
+	const unsigned int n = GF_N(bch);
+	while (v >= n) {
+		v -= n;
+		v = (v & n) + (v >> GF_M(bch));
+	}
+	return v;
+}
+
+/*
+ * shorter and faster modulo function, only works when v < 2N.
+ */
+static inline int mod_s(struct bch_control *bch, unsigned int v)
+{
+	const unsigned int n = GF_N(bch);
+	return (v < n) ? v : v-n;
+}
+
+static inline int deg(unsigned int poly)
+{
+	/* polynomial degree is the most-significant bit index */
+	return fls(poly)-1;
+}
+
+/* Galois field basic operations: multiply, divide, inverse, etc. */
+
+static inline unsigned int gf_mul(struct bch_control *bch, unsigned int a,
+				  unsigned int b)
+{
+	return (a && b) ? bch->a_pow_tab[mod_s(bch, bch->a_log_tab[a]+
+					       bch->a_log_tab[b])] : 0;
+}
+
+static inline unsigned int gf_sqr(struct bch_control *bch, unsigned int a)
+{
+	return a ? bch->a_pow_tab[mod_s(bch, 2*bch->a_log_tab[a])] : 0;
+}
+
+static inline unsigned int a_pow(struct bch_control *bch, int i)
+{
+	return bch->a_pow_tab[modulo(bch, i)];
+}
+
+static inline int a_log(struct bch_control *bch, unsigned int x)
+{
+	return bch->a_log_tab[x];
+}
+
+/*
+ * generate Galois field lookup tables
+ */
+static int build_gf_tables(struct bch_control *bch, unsigned int poly)
+{
+	unsigned int i, x = 1;
+	const unsigned int k = 1 << deg(poly);
+
+	/* primitive polynomial must be of degree m */
+	if (k != (1u << GF_M(bch)))
+		return -1;
+
+	for (i = 0; i < GF_N(bch); i++) {
+		bch->a_pow_tab[i] = x;
+		bch->a_log_tab[x] = i;
+		if (i && (x == 1))
+			/* polynomial is not primitive (a^i=1 with 0<i<2^m-1) */
+			return -1;
+		x <<= 1;
+		if (x & k)
+			x ^= poly;
+	}
+	bch->a_pow_tab[GF_N(bch)] = 1;
+	bch->a_log_tab[0] = 0;
+
+	return 0;
+}
+
+/*
+ * compute generator polynomial remainder tables for fast encoding
+ */
+static void build_mod8_tables(struct bch_control *bch, const uint32_t *g)
+{
+	int i, j, b, d;
+	uint32_t data, hi, lo, *tab;
+	const int l = BCH_ECC_WORDS(bch);
+	const int plen = DIV_ROUND_UP(bch->ecc_bits+1, 32);
+	const int ecclen = DIV_ROUND_UP(bch->ecc_bits, 32);
+
+	memset(bch->mod8_tab, 0, 4*256*l*sizeof(*bch->mod8_tab));
+
+	for (i = 0; i < 256; i++) {
+		/* p(X)=i is a small polynomial of weight <= 8 */
+		for (b = 0; b < 4; b++) {
+			/* we want to compute (p(X).X^(8*b+deg(g))) mod g(X) */
+			tab = bch->mod8_tab + (b*256+i)*l;
+			data = i << (8*b);
+			while (data) {
+				d = deg(data);
+				/* subtract X^d.g(X) from p(X).X^(8*b+deg(g)) */
+				data ^= g[0] >> (31-d);
+				for (j = 0; j < ecclen; j++) {
+					hi = (d < 31) ? g[j] << (d+1) : 0;
+					lo = (j+1 < plen) ?
+						g[j+1] >> (31-d) : 0;
+					tab[j] ^= hi|lo;
+				}
+			}
+		}
+	}
+}
+
+/*
+ * build a base for factoring degree 2 polynomials
+ */
+static int build_deg2_base(struct bch_control *bch)
+{
+	const int m = GF_M(bch);
+	int i, j, r;
+	unsigned int sum, x, y, remaining, ak = 0, xi[m];
+
+	/* find k s.t. Tr(a^k) = 1 and 0 <= k < m */
+	for (i = 0; i < m; i++) {
+		for (j = 0, sum = 0; j < m; j++)
+			sum ^= a_pow(bch, i*(1 << j));
+
+		if (sum) {
+			ak = bch->a_pow_tab[i];
+			break;
+		}
+	}
+	/* find xi, i=0..m-1 such that xi^2+xi = a^i+Tr(a^i).a^k */
+	remaining = m;
+	memset(xi, 0, sizeof(xi));
+
+	for (x = 0; (x <= GF_N(bch)) && remaining; x++) {
+		y = gf_sqr(bch, x)^x;
+		for (i = 0; i < 2; i++) {
+			r = a_log(bch, y);
+			if (y && (r < m) && !xi[r]) {
+				bch->xi_tab[r] = x;
+				xi[r] = 1;
+				remaining--;
+				dbg("x%d = %x\n", r, x);
+				break;
+			}
+			y ^= ak;
+		}
+	}
+	/* should not happen but check anyway */
+	return remaining ? -1 : 0;
+}
+
+static void *bch_alloc(size_t size, int *err)
+{
+	void *ptr;
+
+	ptr = malloc(size);
+	if (ptr == NULL)
+		*err = 1;
+	return ptr;
+}
+
+/*
+ * compute generator polynomial for given (m,t) parameters.
+ */
+static uint32_t *compute_generator_polynomial(struct bch_control *bch)
+{
+	const unsigned int m = GF_M(bch);
+	const unsigned int t = GF_T(bch);
+	int n, err = 0;
+	unsigned int i, j, nbits, r, word, *roots;
+	struct gf_poly *g;
+	uint32_t *genpoly;
+
+	g = bch_alloc(GF_POLY_SZ(m*t), &err);
+	roots = bch_alloc((bch->n+1)*sizeof(*roots), &err);
+	genpoly = bch_alloc(DIV_ROUND_UP(m*t+1, 32)*sizeof(*genpoly), &err);
+
+	if (err) {
+		kfree(genpoly);
+		genpoly = NULL;
+		goto finish;
+	}
+
+	/* enumerate all roots of g(X) */
+	memset(roots , 0, (bch->n+1)*sizeof(*roots));
+	for (i = 0; i < t; i++) {
+		for (j = 0, r = 2*i+1; j < m; j++) {
+			roots[r] = 1;
+			r = mod_s(bch, 2*r);
+		}
+	}
+	/* build generator polynomial g(X) */
+	g->deg = 0;
+	g->c[0] = 1;
+	for (i = 0; i < GF_N(bch); i++) {
+		if (roots[i]) {
+			/* multiply g(X) by (X+root) */
+			r = bch->a_pow_tab[i];
+			g->c[g->deg+1] = 1;
+			for (j = g->deg; j > 0; j--)
+				g->c[j] = gf_mul(bch, g->c[j], r)^g->c[j-1];
+
+			g->c[0] = gf_mul(bch, g->c[0], r);
+			g->deg++;
+		}
+	}
+	/* store left-justified binary representation of g(X) */
+	n = g->deg+1;
+	i = 0;
+
+	while (n > 0) {
+		nbits = (n > 32) ? 32 : n;
+		for (j = 0, word = 0; j < nbits; j++) {
+			if (g->c[n-1-j])
+				word |= 1u << (31-j);
+		}
+		genpoly[i++] = word;
+		n -= nbits;
+	}
+	bch->ecc_bits = g->deg;
+
+finish:
+	kfree(g);
+	kfree(roots);
+
+	return genpoly;
+}
+
+/**
+ *  free_bch - free the BCH control structure
+ *  @bch:    BCH control structure to release
+ */
+static void free_bch(struct bch_control *bch)
+{
+	unsigned int i;
+
+	if (bch) {
+		kfree(bch->a_pow_tab);
+		kfree(bch->a_log_tab);
+		kfree(bch->mod8_tab);
+		kfree(bch->ecc_buf);
+		kfree(bch->ecc_buf2);
+		kfree(bch->xi_tab);
+		kfree(bch->syn);
+		kfree(bch->cache);
+		kfree(bch->elp);
+
+		for (i = 0; i < ARRAY_SIZE(bch->poly_2t); i++)
+			kfree(bch->poly_2t[i]);
+
+		kfree(bch);
+	}
+}
+
+/**
+ * init_bch - initialize a BCH encoder/decoder
+ * @m:          Galois field order, should be in the range 5-15
+ * @t:          maximum error correction capability, in bits
+ * @prim_poly:  user-provided primitive polynomial (or 0 to use default)
+ *
+ * Returns:
+ *  a newly allocated BCH control structure if successful, NULL otherwise
+ *
+ * This initialization can take some time, as lookup tables are built for fast
+ * encoding/decoding; make sure not to call this function from a time critical
+ * path. Usually, init_bch() should be called on module/driver init and
+ * free_bch() should be called to release memory on exit.
+ *
+ * You may provide your own primitive polynomial of degree @m in argument
+ * @prim_poly, or let init_bch() use its default polynomial.
+ *
+ * Once init_bch() has successfully returned a pointer to a newly allocated
+ * BCH control structure, ecc length in bytes is given by member @ecc_bytes of
+ * the structure.
+ */
+static struct bch_control *init_bch(int m, int t, unsigned int prim_poly)
+{
+	int err = 0;
+	unsigned int i, words;
+	uint32_t *genpoly;
+	struct bch_control *bch = NULL;
+
+	const int min_m = 5;
+	const int max_m = 15;
+
+	/* default primitive polynomials */
+	static const unsigned int prim_poly_tab[] = {
+		0x25, 0x43, 0x83, 0x11d, 0x211, 0x409, 0x805, 0x1053, 0x201b,
+		0x402b, 0x8003,
+	};
+
+#if defined(CONFIG_BCH_CONST_PARAMS)
+	if ((m != (CONFIG_BCH_CONST_M)) || (t != (CONFIG_BCH_CONST_T))) {
+		printk(KERN_ERR "bch encoder/decoder was configured to support "
+		       "parameters m=%d, t=%d only!\n",
+		       CONFIG_BCH_CONST_M, CONFIG_BCH_CONST_T);
+		goto fail;
+	}
+#endif
+	if ((m < min_m) || (m > max_m))
+		/*
+		 * values of m greater than 15 are not currently supported;
+		 * supporting m > 15 would require changing table base type
+		 * (uint16_t) and a small patch in matrix transposition
+		 */
+		goto fail;
+
+	/* sanity checks */
+	if ((t < 1) || (m*t >= ((1 << m)-1)))
+		/* invalid t value */
+		goto fail;
+
+	/* select a primitive polynomial for generating GF(2^m) */
+	if (prim_poly == 0)
+		prim_poly = prim_poly_tab[m-min_m];
+
+	bch = malloc(sizeof(*bch));
+	if (bch == NULL)
+		goto fail;
+
+	memset(bch, 0, sizeof(*bch));
+
+	bch->m = m;
+	bch->t = t;
+	bch->n = (1 << m)-1;
+	words  = DIV_ROUND_UP(m*t, 32);
+	bch->ecc_bytes = DIV_ROUND_UP(m*t, 8);
+	bch->a_pow_tab = bch_alloc((1+bch->n)*sizeof(*bch->a_pow_tab), &err);
+	bch->a_log_tab = bch_alloc((1+bch->n)*sizeof(*bch->a_log_tab), &err);
+	bch->mod8_tab  = bch_alloc(words*1024*sizeof(*bch->mod8_tab), &err);
+	bch->ecc_buf   = bch_alloc(words*sizeof(*bch->ecc_buf), &err);
+	bch->ecc_buf2  = bch_alloc(words*sizeof(*bch->ecc_buf2), &err);
+	bch->xi_tab    = bch_alloc(m*sizeof(*bch->xi_tab), &err);
+	bch->syn       = bch_alloc(2*t*sizeof(*bch->syn), &err);
+	bch->cache     = bch_alloc(2*t*sizeof(*bch->cache), &err);
+	bch->elp       = bch_alloc((t+1)*sizeof(struct gf_poly_deg1), &err);
+
+	for (i = 0; i < ARRAY_SIZE(bch->poly_2t); i++)
+		bch->poly_2t[i] = bch_alloc(GF_POLY_SZ(2*t), &err);
+
+	if (err)
+		goto fail;
+
+	err = build_gf_tables(bch, prim_poly);
+	if (err)
+		goto fail;
+
+	/* use generator polynomial for computing encoding tables */
+	genpoly = compute_generator_polynomial(bch);
+	if (genpoly == NULL)
+		goto fail;
+
+	build_mod8_tables(bch, genpoly);
+	kfree(genpoly);
+
+	err = build_deg2_base(bch);
+	if (err)
+		goto fail;
+
+	return bch;
+
+fail:
+	free_bch(bch);
+	return NULL;
+}
+
+static void swap_bits(uint8_t *buf, int len)
+{
+	int i, j;
+
+	for (j = 0; j < len; j++) {
+		uint8_t byte = buf[j];
+
+		buf[j] = 0;
+		for (i = 0; i < 8; i++) {
+			if (byte & (1 << i))
+				buf[j] |= (1 << (7 - i));
+		}
+	}
+}
+
+static uint16_t lfsr_step(uint16_t state, int count)
+{
+	state &= 0x7fff;
+	while (count--)
+		state = ((state >> 1) |
+			 ((((state >> 0) ^ (state >> 1)) & 1) << 14)) & 0x7fff;
+
+	return state;
+}
+
+static uint16_t default_scrambler_seeds[] = {
+	0x2b75, 0x0bd0, 0x5ca3, 0x62d1, 0x1c93, 0x07e9, 0x2162, 0x3a72,
+	0x0d67, 0x67f9, 0x1be7, 0x077d, 0x032f, 0x0dac, 0x2716, 0x2436,
+	0x7922, 0x1510, 0x3860, 0x5287, 0x480f, 0x4252, 0x1789, 0x5a2d,
+	0x2a49, 0x5e10, 0x437f, 0x4b4e, 0x2f45, 0x216e, 0x5cb7, 0x7130,
+	0x2a3f, 0x60e4, 0x4dc9, 0x0ef0, 0x0f52, 0x1bb9, 0x6211, 0x7a56,
+	0x226d, 0x4ea7, 0x6f36, 0x3692, 0x38bf, 0x0c62, 0x05eb, 0x4c55,
+	0x60f4, 0x728c, 0x3b6f, 0x2037, 0x7f69, 0x0936, 0x651a, 0x4ceb,
+	0x6218, 0x79f3, 0x383f, 0x18d9, 0x4f05, 0x5c82, 0x2912, 0x6f17,
+	0x6856, 0x5938, 0x1007, 0x61ab, 0x3e7f, 0x57c2, 0x542f, 0x4f62,
+	0x7454, 0x2eac, 0x7739, 0x42d4, 0x2f90, 0x435a, 0x2e52, 0x2064,
+	0x637c, 0x66ad, 0x2c90, 0x0bad, 0x759c, 0x0029, 0x0986, 0x7126,
+	0x1ca7, 0x1605, 0x386a, 0x27f5, 0x1380, 0x6d75, 0x24c3, 0x0f8e,
+	0x2b7a, 0x1418, 0x1fd1, 0x7dc1, 0x2d8e, 0x43af, 0x2267, 0x7da3,
+	0x4e3d, 0x1338, 0x50db, 0x454d, 0x764d, 0x40a3, 0x42e6, 0x262b,
+	0x2d2e, 0x1aea, 0x2e17, 0x173d, 0x3a6e, 0x71bf, 0x25f9, 0x0a5d,
+	0x7c57, 0x0fbe, 0x46ce, 0x4939, 0x6b17, 0x37bb, 0x3e91, 0x76db,
+};
+
+static uint16_t brom_scrambler_seeds[] = { 0x4a80 };
+
+static void scramble(const struct image_info *info,
+		     int page, uint8_t *data, int datalen)
+{
+	uint16_t state;
+	int i;
+
+	/* Boot0 is always scrambled no matter the command line option. */
+	if (info->boot0) {
+		state = brom_scrambler_seeds[0];
+	} else {
+		unsigned seedmod = info->eraseblock_size / info->page_size;
+
+		/* Bail out earlier if the user didn't ask for scrambling. */
+		if (!info->scramble)
+			return;
+
+		if (seedmod > ARRAY_SIZE(default_scrambler_seeds))
+			seedmod = ARRAY_SIZE(default_scrambler_seeds);
+
+		state = default_scrambler_seeds[page % seedmod];
+	}
+
+	/* Prepare the initial state... */
+	state = lfsr_step(state, 15);
+
+	/* and start scrambling data. */
+	for (i = 0; i < datalen; i++) {
+		data[i] ^= state;
+		state = lfsr_step(state, 8);
+	}
+}
+
+static int write_page(const struct image_info *info, uint8_t *buffer,
+		      FILE *src, FILE *rnd, FILE *dst,
+		      struct bch_control *bch, int page)
+{
+	int steps = info->usable_page_size / info->ecc_step_size;
+	int eccbytes = DIV_ROUND_UP(info->ecc_strength * 14, 8);
+	off_t pos = ftell(dst);
+	size_t pad, cnt;
+	int i;
+
+	if (eccbytes % 2)
+		eccbytes++;
+
+	memset(buffer, 0xff, info->page_size + info->oob_size);
+	cnt = fread(buffer, 1, info->usable_page_size, src);
+	if (!cnt) {
+		if (!feof(src)) {
+			fprintf(stderr,
+				"Failed to read data from the source\n");
+			return -1;
+		} else {
+			return 0;
+		}
+	}
+
+	fwrite(buffer, info->page_size + info->oob_size, 1, dst);
+
+	for (i = 0; i < info->usable_page_size; i++) {
+		if (buffer[i] !=  0xff)
+			break;
+	}
+
+	/* We leave empty pages at 0xff. */
+	if (i == info->usable_page_size)
+		return 0;
+
+	/* Restore the source pointer to read it again. */
+	fseek(src, -cnt, SEEK_CUR);
+
+	/* Randomize unused space if scrambling is required. */
+	if (info->scramble) {
+		int offs;
+
+		if (info->boot0) {
+			offs = steps * (info->ecc_step_size + eccbytes + 4);
+			cnt = info->page_size + info->oob_size - offs;
+			fread(buffer + offs, 1, cnt, rnd);
+		} else {
+			offs = info->page_size + (steps * (eccbytes + 4));
+			cnt = info->page_size + info->oob_size - offs;
+			memset(buffer + offs, 0xff, cnt);
+			scramble(info, page, buffer + offs, cnt);
+		}
+		fseek(dst, pos + offs, SEEK_SET);
+		fwrite(buffer + offs, cnt, 1, dst);
+	}
+
+	for (i = 0; i < steps; i++) {
+		int ecc_offs, data_offs;
+		uint8_t *ecc;
+
+		memset(buffer, 0xff, info->ecc_step_size + eccbytes + 4);
+		ecc = buffer + info->ecc_step_size + 4;
+		if (info->boot0) {
+			data_offs = i * (info->ecc_step_size + eccbytes + 4);
+			ecc_offs = data_offs + info->ecc_step_size + 4;
+		} else {
+			data_offs = i * info->ecc_step_size;
+			ecc_offs = info->page_size + 4 + (i * (eccbytes + 4));
+		}
+
+		cnt = fread(buffer, 1, info->ecc_step_size, src);
+		if (!cnt && !feof(src)) {
+			fprintf(stderr,
+				"Failed to read data from the source\n");
+			return -1;
+		}
+
+		pad = info->ecc_step_size - cnt;
+		if (pad) {
+			if (info->scramble && info->boot0)
+				fread(buffer + cnt, 1, pad, rnd);
+			else
+				memset(buffer + cnt, 0xff, pad);
+		}
+
+		memset(ecc, 0, eccbytes);
+		swap_bits(buffer, info->ecc_step_size + 4);
+		encode_bch(bch, buffer, info->ecc_step_size + 4, ecc);
+		swap_bits(buffer, info->ecc_step_size + 4);
+		swap_bits(ecc, eccbytes);
+		scramble(info, page, buffer, info->ecc_step_size + 4 + eccbytes);
+
+		fseek(dst, pos + data_offs, SEEK_SET);
+		fwrite(buffer, info->ecc_step_size, 1, dst);
+		fseek(dst, pos + ecc_offs - 4, SEEK_SET);
+		fwrite(ecc - 4, eccbytes + 4, 1, dst);
+	}
+
+	/* Fix BBM. */
+	fseek(dst, pos + info->page_size, SEEK_SET);
+	memset(buffer, 0xff, 2);
+	fwrite(buffer, 2, 1, dst);
+
+	/* Make dst pointer point to the next page. */
+	fseek(dst, pos + info->page_size + info->oob_size, SEEK_SET);
+
+	return 0;
+}
+
+static int create_image(const struct image_info *info)
+{
+	off_t page = info->offset / info->page_size;
+	struct bch_control *bch;
+	FILE *src, *dst, *rnd;
+	uint8_t *buffer;
+
+	bch = init_bch(14, info->ecc_strength, BCH_PRIMITIVE_POLY);
+	if (!bch) {
+		fprintf(stderr, "Failed to init the BCH engine\n");
+		return -1;
+	}
+
+	buffer = malloc(info->page_size + info->oob_size);
+	if (!buffer) {
+		fprintf(stderr, "Failed to allocate the NAND page buffer\n");
+		return -1;
+	}
+
+	memset(buffer, 0xff, info->page_size + info->oob_size);
+
+	src = fopen(info->source, "r");
+	if (!src) {
+		fprintf(stderr, "Failed to open source file (%s)\n",
+			info->source);
+		return -1;
+	}
+
+	dst = fopen(info->dest, "w");
+	if (!dst) {
+		fprintf(stderr, "Failed to open dest file (%s)\n", info->dest);
+		return -1;
+	}
+
+	rnd = fopen("/dev/urandom", "r");
+	if (!rnd) {
+		fprintf(stderr, "Failed to open /dev/urandom\n");
+		return -1;
+	}
+
+	while (!feof(src)) {
+		int ret;
+
+		ret = write_page(info, buffer, src, rnd, dst, bch, page++);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static void display_help(int status)
+{
+	fprintf(status == EXIT_SUCCESS ? stdout : stderr,
+	        "Usage: sunxi-nand-image-builder [OPTIONS] source-image output-image\n"
+		"Creates a raw NAND image that can be read by the sunxi NAND controller.\n"
+		"\n"
+		"-h			--help				Display this help and exit\n"
+		"-c <strength>/<step>	--ecc=<strength>/<step>		ECC config\n"
+		"							Valid strengths: 16, 24, 28, 32, 40, 48, 56, 60 and 64\n"
+		"							Valid steps: 512 and 1024\n"
+		"-p <size>		--page-size=<size>		Page size\n"
+		"-o <size>		--oob-size=<size>		OOB size\n"
+		"-u <size>		--usable-page-size=<size>	Usable page size. Only needed for boot0 mode\n"
+		"-e <size>		--eraseblock-size=<size>	Erase block size\n"
+		"-b			--boot0				Build a boot0 image.\n"
+		"-s			--scramble			Scramble data\n"
+		"-a <offset>		--address			Where the image will be programmed.\n"
+		"							This option is only required for non boot0 images that are meant to be programmed at a non eraseblock aligned offset.\n"
+		"\n");
+	exit(status);
+}
+
+static int check_image_info(struct image_info *info)
+{
+	static int valid_ecc_strengths[] = { 16, 24, 28, 32, 40, 48, 56, 60, 64 };
+	int eccbytes, eccsteps;
+	unsigned i;
+
+	if (!info->page_size || !info->oob_size || !info->eraseblock_size ||
+	    !info->usable_page_size)
+		return -EINVAL;
+
+	if (info->ecc_step_size != 512 && info->ecc_step_size != 1024)
+		return -EINVAL;
+
+	for (i = 0; i < ARRAY_SIZE(valid_ecc_strengths); i++) {
+		if (valid_ecc_strengths[i] == info->ecc_strength)
+			break;
+	}
+
+	if (i == ARRAY_SIZE(valid_ecc_strengths))
+		return -EINVAL;
+
+	eccbytes = DIV_ROUND_UP(info->ecc_strength * 14, 8);
+	if (eccbytes % 2)
+		eccbytes++;
+	eccbytes += 4;
+
+	eccsteps = info->usable_page_size / info->ecc_step_size;
+
+	if (info->page_size + info->oob_size <
+	    info->usable_page_size + (eccsteps * (eccbytes)))
+		return -EINVAL;
+
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	struct image_info info;
+
+	memset(&info, 0, sizeof(info));
+	/*
+	 * Process user arguments
+	 */
+	for (;;) {
+		int option_index = 0;
+		char *endptr = NULL;
+		static const struct option long_options[] = {
+			{"help", no_argument, 0, 0},
+			{"ecc", required_argument, 0, 'c'},
+			{"page-size", required_argument, 0, 'p'},
+			{"oob-size", required_argument, 0, 'o'},
+			{"usable-page-size", required_argument, 0, 'u'},
+			{"eraseblock-size", required_argument, 0, 'e'},
+			{"boot0", no_argument, 0, 'b'},
+			{"scramble", no_argument, 0, 's'},
+			{"address", required_argument, 0, 'a'},
+			{0, 0, 0, 0},
+		};
+
+		int c = getopt_long(argc, argv, "c:p:o:u:e:ba:s",
+				long_options, &option_index);
+		if (c == EOF)
+			break;
+
+		switch (c) {
+		case 'h':
+			display_help(0);
+			break;
+		case 's':
+			info.scramble = 1;
+			break;
+		case 'c':
+			info.ecc_strength = strtol(optarg, &endptr, 0);
+			if (endptr || *endptr == '/')
+				info.ecc_step_size = strtol(endptr + 1, NULL, 0);
+			break;
+		case 'p':
+			info.page_size = strtol(optarg, NULL, 0);
+			break;
+		case 'o':
+			info.oob_size = strtol(optarg, NULL, 0);
+			break;
+		case 'u':
+			info.usable_page_size = strtol(optarg, NULL, 0);
+			break;
+		case 'e':
+			info.eraseblock_size = strtol(optarg, NULL, 0);
+			break;
+		case 'b':
+			info.boot0 = 1;
+			break;
+		case 'a':
+			info.offset = strtoull(optarg, NULL, 0);
+			break;
+		case '?':
+			display_help(-1);
+			break;
+		}
+	}
+
+	if ((argc - optind) != 2)
+		display_help(-1);
+
+	info.source = argv[optind];
+	info.dest = argv[optind + 1];
+
+	if (!info.boot0) {
+		info.usable_page_size = info.page_size;
+	} else if (!info.usable_page_size) {
+		if (info.page_size > 8192)
+			info.usable_page_size = 8192;
+		else if (info.page_size > 4096)
+			info.usable_page_size = 4096;
+		else
+			info.usable_page_size = 1024;
+	}
+
+	if (check_image_info(&info))
+		display_help(-1);
+
+	return create_image(&info);
+}