1 files changed, 98 insertions, 0 deletions
diff --git a/libnandfs/ecc.c b/libnandfs/ecc.c
new file mode 100644
index 00000000..1cd86d20
--- /dev/null
+++ b/libnandfs/ecc.c
@@ -0,0 +1,98 @@
+#include "lib9.h"
+#include "nandecc.h"
+
+static uchar ecctab[] = {
+	0x00, 0x55, 0x59, 0x0c, 0x65, 0x30, 0x3c, 0x69, 0x69, 0x3c, 0x30, 0x65, 0x0c, 0x59, 0x55, 0x00,
+	0x95, 0xc0, 0xcc, 0x99, 0xf0, 0xa5, 0xa9, 0xfc, 0xfc, 0xa9, 0xa5, 0xf0, 0x99, 0xcc, 0xc0, 0x95,
+	0x99, 0xcc, 0xc0, 0x95, 0xfc, 0xa9, 0xa5, 0xf0, 0xf0, 0xa5, 0xa9, 0xfc, 0x95, 0xc0, 0xcc, 0x99,
+	0x0c, 0x59, 0x55, 0x00, 0x69, 0x3c, 0x30, 0x65, 0x65, 0x30, 0x3c, 0x69, 0x00, 0x55, 0x59, 0x0c,
+	0xa5, 0xf0, 0xfc, 0xa9, 0xc0, 0x95, 0x99, 0xcc, 0xcc, 0x99, 0x95, 0xc0, 0xa9, 0xfc, 0xf0, 0xa5,
+	0x30, 0x65, 0x69, 0x3c, 0x55, 0x00, 0x0c, 0x59, 0x59, 0x0c, 0x00, 0x55, 0x3c, 0x69, 0x65, 0x30,
+	0x3c, 0x69, 0x65, 0x30, 0x59, 0x0c, 0x00, 0x55, 0x55, 0x00, 0x0c, 0x59, 0x30, 0x65, 0x69, 0x3c,
+	0xa9, 0xfc, 0xf0, 0xa5, 0xcc, 0x99, 0x95, 0xc0, 0xc0, 0x95, 0x99, 0xcc, 0xa5, 0xf0, 0xfc, 0xa9,
+	0xa9, 0xfc, 0xf0, 0xa5, 0xcc, 0x99, 0x95, 0xc0, 0xc0, 0x95, 0x99, 0xcc, 0xa5, 0xf0, 0xfc, 0xa9,
+	0x3c, 0x69, 0x65, 0x30, 0x59, 0x0c, 0x00, 0x55, 0x55, 0x00, 0x0c, 0x59, 0x30, 0x65, 0x69, 0x3c,
+	0x30, 0x65, 0x69, 0x3c, 0x55, 0x00, 0x0c, 0x59, 0x59, 0x0c, 0x00, 0x55, 0x3c, 0x69, 0x65, 0x30,
+	0xa5, 0xf0, 0xfc, 0xa9, 0xc0, 0x95, 0x99, 0xcc, 0xcc, 0x99, 0x95, 0xc0, 0xa9, 0xfc, 0xf0, 0xa5,
+	0x0c, 0x59, 0x55, 0x00, 0x69, 0x3c, 0x30, 0x65, 0x65, 0x30, 0x3c, 0x69, 0x00, 0x55, 0x59, 0x0c,
+	0x99, 0xcc, 0xc0, 0x95, 0xfc, 0xa9, 0xa5, 0xf0, 0xf0, 0xa5, 0xa9, 0xfc, 0x95, 0xc0, 0xcc, 0x99,
+	0x95, 0xc0, 0xcc, 0x99, 0xf0, 0xa5, 0xa9, 0xfc, 0xfc, 0xa9, 0xa5, 0xf0, 0x99, 0xcc, 0xc0, 0x95,
+	0x00, 0x55, 0x59, 0x0c, 0x65, 0x30, 0x3c, 0x69, 0x69, 0x3c, 0x30, 0x65, 0x0c, 0x59, 0x55, 0x00,
+};
+
+ulong
+nandecc(uchar *buf)
+{
+	int cp, zeros, ones, im;
+	int lp, om;
+	int i;
+
+	cp = 0xff;
+	zeros = 0xff;
+	ones = 0xff;
+	for (i = 0; i < 256; i++) {
+		int tabent = ecctab[buf[i]];
+		cp ^= tabent;
+		if (tabent & 1) {
+			zeros ^= ~i;
+			ones ^= i;
+		}
+	}
+	lp = 0;
+	for (im = 0x80, om = 0x8000; im; im >>= 1, om >>= 1) {
+		if (ones & im)
+			lp |= om;
+		om >>= 1;
+		if (zeros & im)
+			lp |= om;
+	}
+	return (((cp & 0xff) | 3) << 16) | lp;
+}
+
+#define CORRECTABLEMASK 0x545555
+
+NandEccError
+nandecccorrect(uchar *buf, ulong calcecc, ulong *storedecc, int reportbad)
+{
+	ulong xorecc;
+	ulong mask;
+	int k;
+
+	if (calcecc == *storedecc)
+		return NandEccErrorGood;
+	if (reportbad)
+		print("nandecccorrect: calculated ecc %.8lux stored ecc %.8lux\n", calcecc, *storedecc);
+	xorecc = calcecc ^ *storedecc;
+	if (((xorecc ^ (xorecc >> 1)) & CORRECTABLEMASK) == CORRECTABLEMASK) {
+		ulong imask;
+		ushort out;
+		ushort omask;
+		int line, col;
+
+		for (imask = 0x800000, omask = 0x800, out = 0; imask; imask >>= 2, omask >>= 1) {
+			if (xorecc & imask)
+				out |= omask;
+		}
+		line = out & 0xff;
+		col = out >> 9;
+		if (reportbad)
+			print("nandecccorrect: single bit error line %d col %d\n", line, col);
+		buf[line] ^= (1 << col);
+		*storedecc = calcecc;
+		return NandEccErrorOneBit;
+	}
+	for (mask = 0x800000, k = 0; mask; mask >>= 1)
+		if (mask & xorecc)
+			k++;
+	if (k == 1) {
+		if (reportbad)
+			print("nandecccorrect: single bit error in ecc\n");
+		// assume the stored ecc was wrong
+		*storedecc = calcecc;
+		return NandEccErrorOneBitInEcc;
+	}
+	if (reportbad)
+		print("nandecccorrect: 2 bit error\n");
+	return NandEccErrorBad;
+}
+