mirror of https://github.com/OpenIPC/firmware.git
285 lines
7.4 KiB
Diff
285 lines
7.4 KiB
Diff
diff -drupN a/fs/yaffs2/yaffs_ecc.c b/fs/yaffs2/yaffs_ecc.c
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--- a/fs/yaffs2/yaffs_ecc.c 1970-01-01 03:00:00.000000000 +0300
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+++ b/fs/yaffs2/yaffs_ecc.c 2022-06-09 05:02:35.000000000 +0300
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@@ -0,0 +1,280 @@
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+/*
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+ * YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
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+ *
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+ * Copyright (C) 2002-2018 Aleph One Ltd.
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+ *
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+ * Created by Charles Manning <charles@aleph1.co.uk>
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+ *
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+ * This program is free software; you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License version 2 as
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+ * published by the Free Software Foundation.
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+ */
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+
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+/*
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+ * This code implements the ECC algorithm used in SmartMedia.
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+ *
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+ * The ECC comprises 22 bits of parity information and is stuffed into 3 bytes.
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+ * The two unused bit are set to 1.
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+ * The ECC can correct single bit errors in a 256-byte page of data. Thus, two
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+ * such ECC blocks are used on a 512-byte NAND page.
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+ *
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+ */
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+
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+#include "yportenv.h"
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+
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+#include "yaffs_ecc.h"
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+
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+/* Table generated by gen-ecc.c
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+ * Using a table means we do not have to calculate p1..p4 and p1'..p4'
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+ * for each byte of data. These are instead provided in a table in bits7..2.
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+ * Bit 0 of each entry indicates whether the entry has an odd or even parity,
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+ * and therefore this bytes influence on the line parity.
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+ */
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+
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+static const unsigned char column_parity_table[] = {
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+ 0x00, 0x55, 0x59, 0x0c, 0x65, 0x30, 0x3c, 0x69,
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+ 0x69, 0x3c, 0x30, 0x65, 0x0c, 0x59, 0x55, 0x00,
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+ 0x95, 0xc0, 0xcc, 0x99, 0xf0, 0xa5, 0xa9, 0xfc,
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+ 0xfc, 0xa9, 0xa5, 0xf0, 0x99, 0xcc, 0xc0, 0x95,
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+ 0x99, 0xcc, 0xc0, 0x95, 0xfc, 0xa9, 0xa5, 0xf0,
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+ 0xf0, 0xa5, 0xa9, 0xfc, 0x95, 0xc0, 0xcc, 0x99,
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+ 0x0c, 0x59, 0x55, 0x00, 0x69, 0x3c, 0x30, 0x65,
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+ 0x65, 0x30, 0x3c, 0x69, 0x00, 0x55, 0x59, 0x0c,
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+ 0xa5, 0xf0, 0xfc, 0xa9, 0xc0, 0x95, 0x99, 0xcc,
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+ 0xcc, 0x99, 0x95, 0xc0, 0xa9, 0xfc, 0xf0, 0xa5,
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+ 0x30, 0x65, 0x69, 0x3c, 0x55, 0x00, 0x0c, 0x59,
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+ 0x59, 0x0c, 0x00, 0x55, 0x3c, 0x69, 0x65, 0x30,
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+ 0x3c, 0x69, 0x65, 0x30, 0x59, 0x0c, 0x00, 0x55,
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+ 0x55, 0x00, 0x0c, 0x59, 0x30, 0x65, 0x69, 0x3c,
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+ 0xa9, 0xfc, 0xf0, 0xa5, 0xcc, 0x99, 0x95, 0xc0,
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+ 0xc0, 0x95, 0x99, 0xcc, 0xa5, 0xf0, 0xfc, 0xa9,
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+ 0xa9, 0xfc, 0xf0, 0xa5, 0xcc, 0x99, 0x95, 0xc0,
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+ 0xc0, 0x95, 0x99, 0xcc, 0xa5, 0xf0, 0xfc, 0xa9,
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+ 0x3c, 0x69, 0x65, 0x30, 0x59, 0x0c, 0x00, 0x55,
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+ 0x55, 0x00, 0x0c, 0x59, 0x30, 0x65, 0x69, 0x3c,
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+ 0x30, 0x65, 0x69, 0x3c, 0x55, 0x00, 0x0c, 0x59,
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+ 0x59, 0x0c, 0x00, 0x55, 0x3c, 0x69, 0x65, 0x30,
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+ 0xa5, 0xf0, 0xfc, 0xa9, 0xc0, 0x95, 0x99, 0xcc,
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+ 0xcc, 0x99, 0x95, 0xc0, 0xa9, 0xfc, 0xf0, 0xa5,
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+ 0x0c, 0x59, 0x55, 0x00, 0x69, 0x3c, 0x30, 0x65,
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+ 0x65, 0x30, 0x3c, 0x69, 0x00, 0x55, 0x59, 0x0c,
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+ 0x99, 0xcc, 0xc0, 0x95, 0xfc, 0xa9, 0xa5, 0xf0,
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+ 0xf0, 0xa5, 0xa9, 0xfc, 0x95, 0xc0, 0xcc, 0x99,
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+ 0x95, 0xc0, 0xcc, 0x99, 0xf0, 0xa5, 0xa9, 0xfc,
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+ 0xfc, 0xa9, 0xa5, 0xf0, 0x99, 0xcc, 0xc0, 0x95,
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+ 0x00, 0x55, 0x59, 0x0c, 0x65, 0x30, 0x3c, 0x69,
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+ 0x69, 0x3c, 0x30, 0x65, 0x0c, 0x59, 0x55, 0x00,
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+};
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+
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+
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+/* Calculate the ECC for a 256-byte block of data */
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+void yaffs_ecc_calc(const unsigned char *data, unsigned char *ecc)
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+{
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+ unsigned int i;
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+ unsigned char col_parity = 0;
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+ unsigned char line_parity = 0;
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+ unsigned char line_parity_prime = 0;
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+ unsigned char t;
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+ unsigned char b;
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+
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+ for (i = 0; i < 256; i++) {
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+ b = column_parity_table[*data++];
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+ col_parity ^= b;
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+
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+ if (b & 0x01) { /* odd number of bits in the byte */
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+ line_parity ^= i;
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+ line_parity_prime ^= ~i;
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+ }
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+ }
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+
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+ ecc[2] = (~col_parity) | 0x03;
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+
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+ t = 0;
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+ if (line_parity & 0x80)
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+ t |= 0x80;
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+ if (line_parity_prime & 0x80)
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+ t |= 0x40;
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+ if (line_parity & 0x40)
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+ t |= 0x20;
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+ if (line_parity_prime & 0x40)
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+ t |= 0x10;
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+ if (line_parity & 0x20)
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+ t |= 0x08;
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+ if (line_parity_prime & 0x20)
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+ t |= 0x04;
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+ if (line_parity & 0x10)
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+ t |= 0x02;
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+ if (line_parity_prime & 0x10)
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+ t |= 0x01;
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+ ecc[1] = ~t;
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+
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+ t = 0;
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+ if (line_parity & 0x08)
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+ t |= 0x80;
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+ if (line_parity_prime & 0x08)
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+ t |= 0x40;
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+ if (line_parity & 0x04)
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+ t |= 0x20;
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+ if (line_parity_prime & 0x04)
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+ t |= 0x10;
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+ if (line_parity & 0x02)
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+ t |= 0x08;
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+ if (line_parity_prime & 0x02)
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+ t |= 0x04;
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+ if (line_parity & 0x01)
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+ t |= 0x02;
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+ if (line_parity_prime & 0x01)
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+ t |= 0x01;
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+ ecc[0] = ~t;
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+
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+}
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+
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+/* Correct the ECC on a 256 byte block of data */
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+
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+int yaffs_ecc_correct(unsigned char *data, unsigned char *read_ecc,
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+ const unsigned char *test_ecc)
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+{
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+ unsigned char d0, d1, d2; /* deltas */
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+
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+ d0 = read_ecc[0] ^ test_ecc[0];
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+ d1 = read_ecc[1] ^ test_ecc[1];
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+ d2 = read_ecc[2] ^ test_ecc[2];
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+
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+ if ((d0 | d1 | d2) == 0)
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+ return 0; /* no error */
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+
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+ if (((d0 ^ (d0 >> 1)) & 0x55) == 0x55 &&
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+ ((d1 ^ (d1 >> 1)) & 0x55) == 0x55 &&
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+ ((d2 ^ (d2 >> 1)) & 0x54) == 0x54) {
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+ /* Single bit (recoverable) error in data */
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+
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+ unsigned byte;
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+ unsigned bit;
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+
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+ bit = byte = 0;
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+
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+ if (d1 & 0x80)
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+ byte |= 0x80;
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+ if (d1 & 0x20)
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+ byte |= 0x40;
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+ if (d1 & 0x08)
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+ byte |= 0x20;
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+ if (d1 & 0x02)
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+ byte |= 0x10;
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+ if (d0 & 0x80)
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+ byte |= 0x08;
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+ if (d0 & 0x20)
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+ byte |= 0x04;
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+ if (d0 & 0x08)
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+ byte |= 0x02;
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+ if (d0 & 0x02)
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+ byte |= 0x01;
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+
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+ if (d2 & 0x80)
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+ bit |= 0x04;
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+ if (d2 & 0x20)
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+ bit |= 0x02;
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+ if (d2 & 0x08)
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+ bit |= 0x01;
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+
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+ data[byte] ^= (1 << bit);
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+
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+ return 1; /* Corrected the error */
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+ }
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+
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+ if ((hweight8(d0) + hweight8(d1) + hweight8(d2)) == 1) {
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+ /* Reccoverable error in ecc */
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+
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+ read_ecc[0] = test_ecc[0];
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+ read_ecc[1] = test_ecc[1];
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+ read_ecc[2] = test_ecc[2];
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+
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+ return 1; /* Corrected the error */
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+ }
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+
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+ /* Unrecoverable error */
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+
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+ return -1;
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+
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+}
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+
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+/*
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+ * ECCxxxOther does ECC calcs on arbitrary n bytes of data
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+ */
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+void yaffs_ecc_calc_other(const unsigned char *data, unsigned n_bytes,
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+ struct yaffs_ecc_other *ecc_other)
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+{
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+ unsigned int i;
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+ unsigned char col_parity = 0;
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+ unsigned line_parity = 0;
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+ unsigned line_parity_prime = 0;
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+ unsigned char b;
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+
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+ for (i = 0; i < n_bytes; i++) {
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+ b = column_parity_table[*data++];
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+ col_parity ^= b;
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+
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+ if (b & 0x01) {
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+ /* odd number of bits in the byte */
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+ line_parity ^= i;
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+ line_parity_prime ^= ~i;
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+ }
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+
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+ }
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+
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+ ecc_other->col_parity = (col_parity >> 2) & 0x3f;
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+ ecc_other->line_parity = line_parity;
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+ ecc_other->line_parity_prime = line_parity_prime;
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+}
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+
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+int yaffs_ecc_correct_other(unsigned char *data, unsigned n_bytes,
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+ struct yaffs_ecc_other *read_ecc,
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+ const struct yaffs_ecc_other *test_ecc)
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+{
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+ unsigned char delta_col; /* column parity delta */
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+ unsigned delta_line; /* line parity delta */
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+ unsigned delta_line_prime; /* line parity delta */
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+ unsigned bit;
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+
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+ delta_col = read_ecc->col_parity ^ test_ecc->col_parity;
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+ delta_line = read_ecc->line_parity ^ test_ecc->line_parity;
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+ delta_line_prime =
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+ read_ecc->line_parity_prime ^ test_ecc->line_parity_prime;
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+
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+ if ((delta_col | delta_line | delta_line_prime) == 0)
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+ return 0; /* no error */
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+
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+ if (delta_line == ~delta_line_prime &&
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+ (((delta_col ^ (delta_col >> 1)) & 0x15) == 0x15)) {
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+ /* Single bit (recoverable) error in data */
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+
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+ bit = 0;
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+
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+ if (delta_col & 0x20)
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+ bit |= 0x04;
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+ if (delta_col & 0x08)
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+ bit |= 0x02;
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+ if (delta_col & 0x02)
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+ bit |= 0x01;
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+
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+ if (delta_line >= n_bytes)
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+ return -1;
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+
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+ data[delta_line] ^= (1 << bit);
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+
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+ return 1; /* corrected */
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+ }
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+
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+ if ((hweight32(delta_line) +
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+ hweight32(delta_line_prime) +
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+ hweight8(delta_col)) == 1) {
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+ /* Reccoverable error in ecc */
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+
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+ *read_ecc = *test_ecc;
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+ return 1; /* corrected */
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+ }
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+
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+ /* Unrecoverable error */
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+
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+ return -1;
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+}
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