davinci_nand: cleanup II (CONFIG_SYS_DAVINCI_BROKEN_ECC)

Remove CONFIG_SYS_DAVINCI_BROKEN_ECC option.  It's not just nasty;
it's also unused by any current boards, and doesn't even match the
main U-Boot distributions from TI (which use soft ECC, or 4-bit ECC
on newer chips that support it).

DaVinci GIT kernels since 2.6.24, and mainline Linux since 2.6.30,
match non-BROKEN code paths for 1-bit HW ECC.  The BROKEN code paths
do seem to partially match what MontaVista/TI kernels (4.0/2.6.10,
and 5.0/2.6.18) do ... but only for small pages.  Large page support
is really broken (and it's unclear just what software it was trying
to match!), and the ECC layout was making three more bytes available
for use by filesystem (or whatever) code.

Since this option itself seems broken, remove it.  Add a comment
about the MV/TI compat issue, and the most straightforward way to
address it (should someone really need to solve it).

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Scott Wood <scottwood@freescale.com>

1 files changed, 13 insertions, 205 deletions

diff --git a/drivers/mtd/nand/davinci_nand.c b/drivers/mtd/nand/davinci_nand.c
index 8b22024..9e7b9dd 100644
--- a/drivers/mtd/nand/davinci_nand.c
+++ b/drivers/mtd/nand/davinci_nand.c
@@ -86,45 +86,12 @@ static void nand_davinci_select_chip(struct mtd_info *mtd, int chip)
 }
 
 #ifdef CONFIG_SYS_NAND_HW_ECC
-#ifdef CONFIG_SYS_DAVINCI_BROKEN_ECC
-/* Linux-compatible ECC uses MTD defaults. */
-/* These layouts are not compatible with Linux or RBL/UBL. */
-#ifdef CONFIG_SYS_NAND_LARGEPAGE
-static struct nand_ecclayout davinci_nand_ecclayout = {
-	.eccbytes = 12,
-	.eccpos = {8, 9, 10, 24, 25, 26, 40, 41, 42, 56, 57, 58},
-	.oobfree = {
-		{.offset = 2, .length = 6},
-		{.offset = 12, .length = 12},
-		{.offset = 28, .length = 12},
-		{.offset = 44, .length = 12},
-		{.offset = 60, .length = 4}
-	}
-};
-#elif defined(CONFIG_SYS_NAND_SMALLPAGE)
-static struct nand_ecclayout davinci_nand_ecclayout = {
-	.eccbytes = 3,
-	.eccpos = {0, 1, 2},
-	.oobfree = {
-		{.offset = 6, .length = 2},
-		{.offset = 8, .length = 8}
-	}
-};
-#else
-#error "Either CONFIG_SYS_NAND_LARGEPAGE or CONFIG_SYS_NAND_SMALLPAGE must be defined!"
-#endif
-#endif /* CONFIG_SYS_DAVINCI_BROKEN_ECC */
 
 static void nand_davinci_enable_hwecc(struct mtd_info *mtd, int mode)
 {
 	int		dummy;
 
 	dummy = emif_regs->NANDF1ECC;
-#ifdef CONFIG_SYS_DAVINCI_BROKEN_ECC
-	dummy = emif_regs->NANDF2ECC;
-	dummy = emif_regs->NANDF3ECC;
-	dummy = emif_regs->NANDF4ECC;
-#endif
 
 	/* FIXME:  only chipselect 0 is supported for now */
 	emif_regs->NANDFCR |= 1 << 8;
@@ -149,29 +116,6 @@ 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 CONFIG_SYS_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;
-
-	n = (this->ecc.size/512);
-
-	region = 1;
-	while (n--) {
-		tmp = nand_davinci_readecc(mtd, region);
-		*ecc_code++ = tmp;
-		*ecc_code++ = tmp >> 16;
-		*ecc_code++ = ((tmp >> 8) & 0x0f) | ((tmp >> 20) & 0xf0);
-		region++;
-	}
-#else
 	const int region = 1;
 
 	tmp = nand_davinci_readecc(mtd, region);
@@ -186,148 +130,26 @@ static int nand_davinci_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u
 	*ecc_code++ = tmp;
 	*ecc_code++ = tmp >>  8;
 	*ecc_code++ = tmp >> 16;
-#endif /* CONFIG_SYS_DAVINCI_BROKEN_ECC */
-	return(0);
-}
-
-#ifdef CONFIG_SYS_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);
-
-	ecc_buf[0] = ~(P64o(tmp) | P64e(tmp) | P32o(tmp) | P32e(tmp) | P16o(tmp) | P16e(tmp) | P8o(tmp) | P8e(tmp));
-	ecc_buf[1] = ~(P1024o(tmp) | P1024e(tmp) | P512o(tmp) | P512e(tmp) | P256o(tmp) | P256e(tmp) | P128o(tmp) | P128e(tmp));
-	ecc_buf[2] = ~( P4o(tmp) | P4e(tmp) | P2o(tmp) | P2e(tmp) | P1o(tmp) | P1e(tmp) | P2048o(tmp) | P2048e(tmp));
-}
-
-static int nand_davinci_compare_ecc(u_int8_t *ecc_nand, u_int8_t *ecc_calc, u_int8_t *page_data)
-{
-	u_int32_t	i;
-	u_int8_t	tmp0_bit[8], tmp1_bit[8], tmp2_bit[8];
-	u_int8_t	comp0_bit[8], comp1_bit[8], comp2_bit[8];
-	u_int8_t	ecc_bit[24];
-	u_int8_t	ecc_sum = 0;
-	u_int8_t	find_bit = 0;
-	u_int32_t	find_byte = 0;
-	int		is_ecc_ff;
-
-	is_ecc_ff = ((*ecc_nand == 0xff) && (*(ecc_nand + 1) == 0xff) && (*(ecc_nand + 2) == 0xff));
-
-	nand_davinci_gen_true_ecc(ecc_nand);
-	nand_davinci_gen_true_ecc(ecc_calc);
-
-	for (i = 0; i <= 2; i++) {
-		*(ecc_nand + i) = ~(*(ecc_nand + i));
-		*(ecc_calc + i) = ~(*(ecc_calc + i));
-	}
-
-	for (i = 0; i < 8; i++) {
-		tmp0_bit[i] = *ecc_nand % 2;
-		*ecc_nand = *ecc_nand / 2;
-	}
-
-	for (i = 0; i < 8; i++) {
-		tmp1_bit[i] = *(ecc_nand + 1) % 2;
-		*(ecc_nand + 1) = *(ecc_nand + 1) / 2;
-	}
-
-	for (i = 0; i < 8; i++) {
-		tmp2_bit[i] = *(ecc_nand + 2) % 2;
-		*(ecc_nand + 2) = *(ecc_nand + 2) / 2;
-	}
 
-	for (i = 0; i < 8; i++) {
-		comp0_bit[i] = *ecc_calc % 2;
-		*ecc_calc = *ecc_calc / 2;
-	}
-
-	for (i = 0; i < 8; i++) {
-		comp1_bit[i] = *(ecc_calc + 1) % 2;
-		*(ecc_calc + 1) = *(ecc_calc + 1) / 2;
-	}
-
-	for (i = 0; i < 8; i++) {
-		comp2_bit[i] = *(ecc_calc + 2) % 2;
-		*(ecc_calc + 2) = *(ecc_calc + 2) / 2;
-	}
-
-	for (i = 0; i< 6; i++)
-		ecc_bit[i] = tmp2_bit[i + 2] ^ comp2_bit[i + 2];
-
-	for (i = 0; i < 8; i++)
-		ecc_bit[i + 6] = tmp0_bit[i] ^ comp0_bit[i];
-
-	for (i = 0; i < 8; i++)
-		ecc_bit[i + 14] = tmp1_bit[i] ^ comp1_bit[i];
-
-	ecc_bit[22] = tmp2_bit[0] ^ comp2_bit[0];
-	ecc_bit[23] = tmp2_bit[1] ^ comp2_bit[1];
-
-	for (i = 0; i < 24; i++)
-		ecc_sum += ecc_bit[i];
+	/* NOTE:  the above code matches mainline Linux:
+	 *	.PQR.stu ==> ~PQRstu
+	 *
+	 * MontaVista/TI kernels encode those bytes differently, use
+	 * complicated (and allegedly sometimes-wrong) correction code,
+	 * and usually shipped with U-Boot that uses software ECC:
+	 *	.PQR.stu ==> PsQRtu
+	 *
+	 * If you need MV/TI compatible NAND I/O in U-Boot, it should
+	 * be possible to (a) change the mangling above, (b) reverse
+	 * that mangling in nand_davinci_correct_data() below.
+	 */
 
-	switch (ecc_sum) {
-		case 0:
-			/* Not reached because this function is not called if
-			   ECC values are equal */
-			return 0;
-		case 1:
-			/* Uncorrectable error */
-			MTDDEBUG (MTD_DEBUG_LEVEL0,
-			          "ECC UNCORRECTED_ERROR 1\n");
-			return(-1);
-		case 12:
-			/* Correctable error */
-			find_byte = (ecc_bit[23] << 8) +
-				(ecc_bit[21] << 7) +
-				(ecc_bit[19] << 6) +
-				(ecc_bit[17] << 5) +
-				(ecc_bit[15] << 4) +
-				(ecc_bit[13] << 3) +
-				(ecc_bit[11] << 2) +
-				(ecc_bit[9]  << 1) +
-				ecc_bit[7];
-
-			find_bit = (ecc_bit[5] << 2) + (ecc_bit[3] << 1) + ecc_bit[1];
-
-			MTDDEBUG (MTD_DEBUG_LEVEL0, "Correcting single bit ECC "
-			          "error at offset: %d, bit: %d\n",
-			          find_byte, find_bit);
-
-			page_data[find_byte] ^= (1 << find_bit);
-
-			return(0);
-		default:
-			if (is_ecc_ff) {
-				if (ecc_calc[0] == 0 && ecc_calc[1] == 0 && ecc_calc[2] == 0)
-					return(0);
-			}
-			MTDDEBUG (MTD_DEBUG_LEVEL0,
-			          "UNCORRECTED_ERROR default\n");
-			return(-1);
-	}
+	return 0;
 }
-#endif /* CONFIG_SYS_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 = mtd->priv;
-#ifdef CONFIG_SYS_DAVINCI_BROKEN_ECC
-	int			block_count = 0, i, rc;
-
-	block_count = (this->ecc.size/512);
-	for (i = 0; i < block_count; i++) {
-		if (memcmp(read_ecc, calc_ecc, 3) != 0) {
-			rc = nand_davinci_compare_ecc(read_ecc, calc_ecc, dat);
-			if (rc < 0) {
-				return(rc);
-			}
-		}
-		read_ecc += 3;
-		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) |
@@ -361,7 +183,6 @@ static int nand_davinci_correct_data(struct mtd_info *mtd, u_char *dat, u_char *
 			return -1;
 		}
 	}
-#endif /* CONFIG_SYS_DAVINCI_BROKEN_ECC */
 	return(0);
 }
 #endif /* CONFIG_SYS_NAND_HW_ECC */
@@ -416,21 +237,8 @@ int board_nand_init(struct nand_chip *nand)
 #endif
 #ifdef CONFIG_SYS_NAND_HW_ECC
 	nand->ecc.mode = NAND_ECC_HW;
-#ifdef CONFIG_SYS_DAVINCI_BROKEN_ECC
-	nand->ecc.layout  = &davinci_nand_ecclayout;
-#ifdef CONFIG_SYS_NAND_LARGEPAGE
-	nand->ecc.size = 2048;
-	nand->ecc.bytes = 12;
-#elif defined(CONFIG_SYS_NAND_SMALLPAGE)
-	nand->ecc.size = 512;
-	nand->ecc.bytes = 3;
-#else
-#error "Either CONFIG_SYS_NAND_LARGEPAGE or CONFIG_SYS_NAND_SMALLPAGE must be defined!"
-#endif
-#else
 	nand->ecc.size = 512;
 	nand->ecc.bytes = 3;
-#endif /* CONFIG_SYS_DAVINCI_BROKEN_ECC */
 	nand->ecc.calculate = nand_davinci_calculate_ecc;
 	nand->ecc.correct  = nand_davinci_correct_data;
 	nand->ecc.hwctl  = nand_davinci_enable_hwecc;