diff --git a/cpu/arm926ejs/davinci/nand.c b/cpu/arm926ejs/davinci/nand.c
index 5a1da633d3..f7cf0c9ec2 100644
--- a/cpu/arm926ejs/davinci/nand.c
+++ b/cpu/arm926ejs/davinci/nand.c
@@ -88,6 +88,9 @@ static void nand_davinci_select_chip(struct mtd_info *mtd, int chip)
}
#ifdef CFG_NAND_HW_ECC
+#ifdef CFG_DAVINCI_BROKEN_ECC
+/* Linux-compatible ECC uses MTD defaults. */
+/* These layouts are not compatible with Linux or RBL/UBL. */
#ifdef CFG_NAND_LARGEPAGE
static struct nand_ecclayout davinci_nand_ecclayout = {
.eccbytes = 12,
@@ -112,6 +115,7 @@ static struct nand_ecclayout davinci_nand_ecclayout = {
#else
#error "Either CFG_NAND_LARGEPAGE or CFG_NAND_SMALLPAGE must be defined!"
#endif
+#endif /* CFG_DAVINCI_BROKEN_ECC */
static void nand_davinci_enable_hwecc(struct mtd_info *mtd, int mode)
{
@@ -150,6 +154,15 @@ static u_int32_t nand_davinci_readecc(struct mtd_info *mtd, u_int32_t region)
static int nand_davinci_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code)
{
u_int32_t tmp;
+#ifdef CFG_DAVINCI_BROKEN_ECC
+ /*
+ * This is not how you should read ECCs on large page Davinci devices.
+ * The region parameter gets you ECCs for flash chips on different chip
+ * selects, not the 4x512 byte pages in a 2048 byte page.
+ *
+ * Preserved for backwards compatibility though.
+ */
+
int region, n;
struct nand_chip *this = mtd->priv;
@@ -163,9 +176,26 @@ static int nand_davinci_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u
*ecc_code++ = ((tmp >> 8) & 0x0f) | ((tmp >> 20) & 0xf0);
region++;
}
+#else
+ const int region = 1;
+
+ tmp = nand_davinci_readecc(mtd, region);
+
+ /* Squeeze 4 bytes ECC into 3 bytes by removing RESERVED bits
+ * and shifting. RESERVED bits are 31 to 28 and 15 to 12. */
+ tmp = (tmp & 0x00000fff) | ((tmp & 0x0fff0000) >> 4);
+
+ /* Invert so that erased block ECC is correct */
+ tmp = ~tmp;
+
+ *ecc_code++ = tmp;
+ *ecc_code++ = tmp >> 8;
+ *ecc_code++ = tmp >> 16;
+#endif /* CFG_DAVINCI_BROKEN_ECC */
return(0);
}
+#ifdef CFG_DAVINCI_BROKEN_ECC
static void nand_davinci_gen_true_ecc(u_int8_t *ecc_buf)
{
u_int32_t tmp = ecc_buf[0] | (ecc_buf[1] << 16) | ((ecc_buf[2] & 0xf0) << 20) | ((ecc_buf[2] & 0x0f) << 8);
@@ -282,13 +312,14 @@ static int nand_davinci_compare_ecc(u_int8_t *ecc_nand, u_int8_t *ecc_calc, u_in
return(-1);
}
}
+#endif /* CFG_DAVINCI_BROKEN_ECC */
static int nand_davinci_correct_data(struct mtd_info *mtd, u_char *dat, u_char *read_ecc, u_char *calc_ecc)
{
- struct nand_chip *this;
+ struct nand_chip *this = mtd->priv;
+#ifdef CFG_DAVINCI_BROKEN_ECC
int block_count = 0, i, rc;
- this = mtd->priv;
block_count = (this->ecc.size/512);
for (i = 0; i < block_count; i++) {
if (memcmp(read_ecc, calc_ecc, 3) != 0) {
@@ -301,9 +332,44 @@ static int nand_davinci_correct_data(struct mtd_info *mtd, u_char *dat, u_char *
calc_ecc += 3;
dat += 512;
}
+#else
+ u_int32_t ecc_nand = read_ecc[0] | (read_ecc[1] << 8) |
+ (read_ecc[2] << 16);
+ u_int32_t ecc_calc = calc_ecc[0] | (calc_ecc[1] << 8) |
+ (calc_ecc[2] << 16);
+ u_int32_t diff = ecc_calc ^ ecc_nand;
+
+ if (diff) {
+ if ((((diff >> 12) ^ diff) & 0xfff) == 0xfff) {
+ /* Correctable error */
+ if ((diff >> (12 + 3)) < this->ecc.size) {
+ uint8_t find_bit = 1 << ((diff >> 12) & 7);
+ uint32_t find_byte = diff >> (12 + 3);
+
+ dat[find_byte] ^= find_bit;
+ MTDDEBUG(MTD_DEBUG_LEVEL0, "Correcting single "
+ "bit ECC error at offset: %d, bit: "
+ "%d\n", find_byte, find_bit);
+ return 1;
+ } else {
+ return -1;
+ }
+ } else if (!(diff & (diff - 1))) {
+ /* Single bit ECC error in the ECC itself,
+ nothing to fix */
+ MTDDEBUG(MTD_DEBUG_LEVEL0, "Single bit ECC error in "
+ "ECC.\n");
+ return 1;
+ } else {
+ /* Uncorrectable error */
+ MTDDEBUG(MTD_DEBUG_LEVEL0, "ECC UNCORRECTED_ERROR 1\n");
+ return -1;
+ }
+ }
+#endif /* CFG_DAVINCI_BROKEN_ECC */
return(0);
}
-#endif
+#endif /* CFG_NAND_HW_ECC */
static int nand_davinci_dev_ready(struct mtd_info *mtd)
{
@@ -370,6 +436,8 @@ int board_nand_init(struct nand_chip *nand)
#endif
#ifdef CFG_NAND_HW_ECC
nand->ecc.mode = NAND_ECC_HW;
+#ifdef CFG_DAVINCI_BROKEN_ECC
+ nand->ecc.layout = &davinci_nand_ecclayout;
#ifdef CFG_NAND_LARGEPAGE
nand->ecc.size = 2048;
nand->ecc.bytes = 12;
@@ -379,13 +447,16 @@ int board_nand_init(struct nand_chip *nand)
#else
#error "Either CFG_NAND_LARGEPAGE or CFG_NAND_SMALLPAGE must be defined!"
#endif
- nand->ecc.layout = &davinci_nand_ecclayout;
+#else
+ nand->ecc.size = 512;
+ nand->ecc.bytes = 3;
+#endif /* CFG_DAVINCI_BROKEN_ECC */
nand->ecc.calculate = nand_davinci_calculate_ecc;
nand->ecc.correct = nand_davinci_correct_data;
nand->ecc.hwctl = nand_davinci_enable_hwecc;
#else
nand->ecc.mode = NAND_ECC_SOFT;
-#endif
+#endif /* CFG_NAND_HW_ECC */
/* Set address of hardware control function */
nand->cmd_ctrl = nand_davinci_hwcontrol;
diff --git a/doc/README.nand b/doc/README.nand
index 171380e274..6dac24cd90 100644
--- a/doc/README.nand
+++ b/doc/README.nand
@@ -174,6 +174,14 @@ More Definitions:
#define NAND_MAX_FLOORS 1
#define NAND_MAX_CHIPS 1
+ #define CFG_DAVINCI_BROKEN_ECC
+ Versions of U-Boot <= 1.3.3 and Montavista Linux kernels
+ generated bogus ECCs on large-page NAND. Both large and small page
+ NAND ECCs were incompatible with the Linux davinci git tree (since
+ NAND was integrated in 2.6.24).
+ Turn this ON if you want backwards compatibility.
+ Turn this OFF if you want U-Boot and the Linux davinci git kernel
+ to use the same ECC format.
NOTE:
=====