From d1f9fa8a3a4c2ab735c7bfaec11f61159811b389 Mon Sep 17 00:00:00 2001
From: marcan <marcan@marcansoft.com>
Date: Sat, 7 Mar 2009 17:31:45 +0100
Subject: [PATCH] Add NAND ECC correction to miniios and use for boot2 loads

---
 boot2.c |  5 +++++
 main.c  |  1 -
 nand.c  | 42 ++++++++++++++++++++++++++++++++++++++++++
 nand.h  |  6 ++++++
 4 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/boot2.c b/boot2.c
index 756dd2b..47f6a14 100644
--- a/boot2.c
+++ b/boot2.c
@@ -42,6 +42,10 @@ void boot2_init() {
 	for (i = 0x40; i < 0x140; i++, ptr += 2048) {
 		nand_read_page(i, ptr, ecc);
 		nand_wait();
+		if(nand_correct(i, ptr, ecc) < 0) {
+			gecko_printf("boot2 is corrupted, cannot load!\n");
+			return;
+		}
 	}
 
 	if (hdr->len != sizeof(struct wadheader))
@@ -75,6 +79,7 @@ void boot2_init() {
 
 	memcpy(boot2, cntptr, datalen);
 	boot2_initialized = 1;
+	gecko_printf("boot2 loaded\n");
 }
 
 static u32 match[] = {
diff --git a/main.c b/main.c
index c10872d..cf5f92f 100644
--- a/main.c
+++ b/main.c
@@ -178,7 +178,6 @@ void *_main(void *base)
 	gecko_puts("NAND initialized.\n");
 
 	boot2_init();
-	gecko_puts("Boot2 loaded to memory.\n");
 
 	gecko_puts("Initializing IPC...\n");
 	ipc_initialize();
diff --git a/nand.c b/nand.c
index 56ba728..5ca9422 100644
--- a/nand.c
+++ b/nand.c
@@ -200,6 +200,48 @@ void nand_initialize(void)
 	irq_enable(IRQ_NAND);
 }
 
+int nand_correct(u32 pageno, void *data, void *ecc)
+{
+	u8 *dp = (u8*)data;
+	u32 *ecc_read = (u32*)((u8*)ecc)+0x30;
+	u32 *ecc_calc = (u32*)((u8*)ecc)+0x40;
+	int i;
+	int uncorrectable = 0;
+	int corrected = 0;
+	
+	for(i=0;i<4;i++) {
+		u32 syndrome = *ecc_read ^ *ecc_calc; //calculate ECC syncrome
+		if(syndrome) {
+			if(!((syndrome-1)&syndrome)) {
+				// single-bit error in ECC
+				corrected++;
+			} else {
+				// byteswap and extract odd and even halves
+				u16 even = (syndrome >> 24) | ((syndrome >> 8) & 0xf00);
+				u16 odd = ((syndrome << 8) & 0xf00) | ((syndrome >> 8) & 0x0ff);
+				if((even ^ odd) != 0xfff) {
+					// oops, can't fix this one
+					uncorrectable++;
+				} else {
+					// fix the bad bit
+					dp[odd >> 3] ^= 1<<(odd&7);
+					corrected++;
+				}
+			}
+		}
+		dp += 0x200;
+		ecc_read++;
+		ecc_calc++;
+	}
+	if(uncorrectable || corrected)
+		gecko_printf("ECC stats for NAND page 0x%x: %d uncorrectable, %d corrected\n", uncorrectable, corrected);
+	if(uncorrectable)
+		return NAND_ECC_UNCORRECTABLE;
+	if(corrected)
+		return NAND_ECC_CORRECTED;
+	return NAND_ECC_OK;
+}
+
 void nand_ipc(volatile ipc_request *req)
 {
 	if (ipc_code != 0 || ipc_tag != 0) {
diff --git a/nand.h b/nand.h
index e0f073d..171443e 100644
--- a/nand.h
+++ b/nand.h
@@ -17,6 +17,12 @@ void nand_wait(void);
 
 void nand_read_cluster(u32 clusterno, void *data);
 
+#define NAND_ECC_OK 0
+#define NAND_ECC_CORRECTED 1
+#define NAND_ECC_UNCORRECTABLE -1
+
+int nand_correct(u32 pageno, void *data, void *ecc);
+
 void nand_initialize();
 
 void nand_ipc(volatile ipc_request *req);