1 files changed, 250 insertions, 0 deletions

diff --git a/drivers/mtd/nand/nand_ecc.c b/drivers/mtd/nand/nand_ecc.c
new file mode 100644
index 000000000000..2e341b75437a
--- /dev/null
+++ b/drivers/mtd/nand/nand_ecc.c
@@ -0,0 +1,250 @@
+/*
+ * This file contains an ECC algorithm from Toshiba that detects and
+ * corrects 1 bit errors in a 256 byte block of data.
+ *
+ * drivers/mtd/nand/nand_ecc.c
+ *
+ * Copyright (C) 2000-2004 Steven J. Hill (sjhill@realitydiluted.com)
+ *                         Toshiba America Electronics Components, Inc.
+ *
+ * $Id: nand_ecc.c,v 1.14 2004/06/16 15:34:37 gleixner Exp $
+ *
+ * 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.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this file; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ * 
+ * As a special exception, if other files instantiate templates or use
+ * macros or inline functions from these files, or you compile these
+ * files and link them with other works to produce a work based on these
+ * files, these files do not by themselves cause the resulting work to be
+ * covered by the GNU General Public License. However the source code for
+ * these files must still be made available in accordance with section (3)
+ * of the GNU General Public License.
+ * 
+ * This exception does not invalidate any other reasons why a work based on
+ * this file might be covered by the GNU General Public License.
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mtd/nand_ecc.h>
+
+/*
+ * Pre-calculated 256-way 1 byte column parity
+ */
+static const u_char nand_ecc_precalc_table[] = {
+        0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
+        0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
+        0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
+        0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
+        0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
+        0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
+        0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
+        0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
+        0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
+        0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
+        0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
+        0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
+        0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
+        0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
+        0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
+        0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
+};
+
+
+/**
+ * nand_trans_result - [GENERIC] create non-inverted ECC
+ * @reg2:       line parity reg 2
+ * @reg3:       line parity reg 3
+ * @ecc_code:   ecc 
+ *
+ * Creates non-inverted ECC code from line parity
+ */
+static void nand_trans_result(u_char reg2, u_char reg3,
+        u_char *ecc_code)
+{
+        u_char a, b, i, tmp1, tmp2;
+        
+        /* Initialize variables */
+        a = b = 0x80;
+        tmp1 = tmp2 = 0;
+        
+        /* Calculate first ECC byte */
+        for (i = 0; i < 4; i++) {
+                if (reg3 & a)           /* LP15,13,11,9 --> ecc_code[0] */
+                        tmp1 |= b;
+                b >>= 1;
+                if (reg2 & a)           /* LP14,12,10,8 --> ecc_code[0] */
+                        tmp1 |= b;
+                b >>= 1;
+                a >>= 1;
+        }
+        
+        /* Calculate second ECC byte */
+        b = 0x80;
+        for (i = 0; i < 4; i++) {
+                if (reg3 & a)           /* LP7,5,3,1 --> ecc_code[1] */
+                        tmp2 |= b;
+                b >>= 1;
+                if (reg2 & a)           /* LP6,4,2,0 --> ecc_code[1] */
+                        tmp2 |= b;
+                b >>= 1;
+                a >>= 1;
+        }
+        
+        /* Store two of the ECC bytes */
+        ecc_code[0] = tmp1;
+        ecc_code[1] = tmp2;
+}
+
+/**
+ * nand_calculate_ecc - [NAND Interface] Calculate 3 byte ECC code for 256 byte block
+ * @mtd:        MTD block structure
+ * @dat:        raw data
+ * @ecc_code:   buffer for ECC
+ */
+int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code)
+{
+        u_char idx, reg1, reg2, reg3;
+        int j;
+        
+        /* Initialize variables */
+        reg1 = reg2 = reg3 = 0;
+        ecc_code[0] = ecc_code[1] = ecc_code[2] = 0;
+        
+        /* Build up column parity */ 
+        for(j = 0; j < 256; j++) {
+                
+                /* Get CP0 - CP5 from table */
+                idx = nand_ecc_precalc_table[dat[j]];
+                reg1 ^= (idx & 0x3f);
+                
+                /* All bit XOR = 1 ? */
+                if (idx & 0x40) {
+                        reg3 ^= (u_char) j;
+                        reg2 ^= ~((u_char) j);
+                }
+        }
+        
+        /* Create non-inverted ECC code from line parity */
+        nand_trans_result(reg2, reg3, ecc_code);
+        
+        /* Calculate final ECC code */
+        ecc_code[0] = ~ecc_code[0];
+        ecc_code[1] = ~ecc_code[1];
+        ecc_code[2] = ((~reg1) << 2) | 0x03;
+        return 0;
+}
+
+/**
+ * nand_correct_data - [NAND Interface] Detect and correct bit error(s)
+ * @mtd:        MTD block structure
+ * @dat:        raw data read from the chip
+ * @read_ecc:   ECC from the chip
+ * @calc_ecc:   the ECC calculated from raw data
+ *
+ * Detect and correct a 1 bit error for 256 byte block
+ */
+int nand_correct_data(struct mtd_info *mtd, u_char *dat, u_char *read_ecc, u_char *calc_ecc)
+{
+        u_char a, b, c, d1, d2, d3, add, bit, i;
+        
+        /* Do error detection */ 
+        d1 = calc_ecc[0] ^ read_ecc[0];
+        d2 = calc_ecc[1] ^ read_ecc[1];
+        d3 = calc_ecc[2] ^ read_ecc[2];
+        
+        if ((d1 | d2 | d3) == 0) {
+                /* No errors */
+                return 0;
+        }
+        else {
+                a = (d1 ^ (d1 >> 1)) & 0x55;
+                b = (d2 ^ (d2 >> 1)) & 0x55;
+                c = (d3 ^ (d3 >> 1)) & 0x54;
+                
+                /* Found and will correct single bit error in the data */
+                if ((a == 0x55) && (b == 0x55) && (c == 0x54)) {
+                        c = 0x80;
+                        add = 0;
+                        a = 0x80;
+                        for (i=0; i<4; i++) {
+                                if (d1 & c)
+                                        add |= a;
+                                c >>= 2;
+                                a >>= 1;
+                        }
+                        c = 0x80;
+                        for (i=0; i<4; i++) {
+                                if (d2 & c)
+                                        add |= a;
+                                c >>= 2;
+                                a >>= 1;
+                        }
+                        bit = 0;
+                        b = 0x04;
+                        c = 0x80;
+                        for (i=0; i<3; i++) {
+                                if (d3 & c)
+                                        bit |= b;
+                                c >>= 2;
+                                b >>= 1;
+                        }
+                        b = 0x01;
+                        a = dat[add];
+                        a ^= (b << bit);
+                        dat[add] = a;
+                        return 1;
+                }
+                else {
+                        i = 0;
+                        while (d1) {
+                                if (d1 & 0x01)
+                                        ++i;
+                                d1 >>= 1;
+                        }
+                        while (d2) {
+                                if (d2 & 0x01)
+                                        ++i;
+                                d2 >>= 1;
+                        }
+                        while (d3) {
+                                if (d3 & 0x01)
+                                        ++i;
+                                d3 >>= 1;
+                        }
+                        if (i == 1) {
+                                /* ECC Code Error Correction */
+                                read_ecc[0] = calc_ecc[0];
+                                read_ecc[1] = calc_ecc[1];
+                                read_ecc[2] = calc_ecc[2];
+                                return 2;
+                        }
+                        else {
+                                /* Uncorrectable Error */
+                                return -1;
+                        }
+                }
+        }
+        
+        /* Should never happen */
+        return -1;
+}
+
+EXPORT_SYMBOL(nand_calculate_ecc);
+EXPORT_SYMBOL(nand_correct_data);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Steven J. Hill <sjhill@realitydiluted.com>");
+MODULE_DESCRIPTION("Generic NAND ECC support");