[U-Boot] [PATCH 07/12] mtd: nand: s3c: Add missing correction and select_chip functions

[Marek Vasut <marex@denx.de>]

Implant a missing ECC correction implementation and select_chip
implementation from Linux.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Lukasz Majewski <l.majewski@samsung.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Cc: Scott Wood <scottwood@freescale.com>
Cc: Vladimir Zapolskiy <vz@mleia.com>
---
 drivers/mtd/nand/s3c2410_nand.c | 89 ++++++++++++++++++++++++++++++++++++++---
 1 file changed, 84 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/nand/s3c2410_nand.c b/drivers/mtd/nand/s3c2410_nand.c
index c71f874..511e85b 100644
--- a/drivers/mtd/nand/s3c2410_nand.c
+++ b/drivers/mtd/nand/s3c2410_nand.c
@@ -157,16 +157,93 @@ static int s3c24x0_nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat,
 static int s3c24x0_nand_correct_data(struct mtd_info *mtd, u_char *dat,
 				     u_char *read_ecc, u_char *calc_ecc)
 {
-	if (read_ecc[0] == calc_ecc[0] &&
-	    read_ecc[1] == calc_ecc[1] &&
-	    read_ecc[2] == calc_ecc[2])
+	unsigned int diff0, diff1, diff2;
+	unsigned int bit, byte;
+
+	debug("%s(%p,%p,%p,%p)\n", __func__, mtd, dat, read_ecc, calc_ecc);
+
+	diff0 = read_ecc[0] ^ calc_ecc[0];
+	diff1 = read_ecc[1] ^ calc_ecc[1];
+	diff2 = read_ecc[2] ^ calc_ecc[2];
+
+	debug("%s: rd %*phN calc %*phN diff %02x%02x%02x\n",
+	      __func__, 3, read_ecc, 3, calc_ecc,
+	      diff0, diff1, diff2);
+
+	if (diff0 == 0 && diff1 == 0 && diff2 == 0)
+		return 0;		/* ECC is ok */
+
+	/* sometimes people do not think about using the ECC, so check
+	 * to see if we have an 0xff,0xff,0xff read ECC and then ignore
+	 * the error, on the assumption that this is an un-eccd page.
+	 */
+	if (read_ecc[0] == 0xff && read_ecc[1] == 0xff && read_ecc[2] == 0xff
+	    /*&& info->platform->ignore_unset_ecc*/)
 		return 0;
 
-	printf("s3c24x0_nand_correct_data: not implemented\n");
+	/* Can we correct this ECC (ie, one row and column change).
+	 * Note, this is similar to the 256 error code on smartmedia */
+
+	if (((diff0 ^ (diff0 >> 1)) & 0x55) == 0x55 &&
+	    ((diff1 ^ (diff1 >> 1)) & 0x55) == 0x55 &&
+	    ((diff2 ^ (diff2 >> 1)) & 0x55) == 0x55) {
+		/* calculate the bit position of the error */
+
+		bit  = ((diff2 >> 3) & 1) |
+		       ((diff2 >> 4) & 2) |
+		       ((diff2 >> 5) & 4);
+
+		/* calculate the byte position of the error */
+
+		byte = ((diff2 << 7) & 0x100) |
+		       ((diff1 << 0) & 0x80)  |
+		       ((diff1 << 1) & 0x40)  |
+		       ((diff1 << 2) & 0x20)  |
+		       ((diff1 << 3) & 0x10)  |
+		       ((diff0 >> 4) & 0x08)  |
+		       ((diff0 >> 3) & 0x04)  |
+		       ((diff0 >> 2) & 0x02)  |
+		       ((diff0 >> 1) & 0x01);
+
+		debug("correcting error bit %d, byte %d\n", bit, byte);
+
+		dat[byte] ^= (1 << bit);
+		return 1;
+	}
+
+	/* if there is only one bit difference in the ECC, then
+	 * one of only a row or column parity has changed, which
+	 * means the error is most probably in the ECC itself */
+
+	diff0 |= (diff1 << 8);
+	diff0 |= (diff2 << 16);
+
+	if ((diff0 & ~(1<<fls(diff0))) == 0)
+		return 1;
+
 	return -1;
 }
 #endif
 
+static void s3c24x0_nand_select_chip(struct mtd_info *mtd, int chip)
+{
+	struct s3c24x0_nand *nand = s3c24x0_get_base_nand();
+	uint32_t sel_reg, sel_bit;
+
+#ifdef CONFIG_S3C2410
+	sel_reg = (uint32_t)&nand->nfconf;
+	sel_bit = S3C2410_NFCONF_nFCE;
+#else
+	sel_reg = (uint32_t)&nand->nfcont;
+	sel_bit = S3C2440_NFCONT_nFCE;
+#endif
+
+	if (chip == -1)
+		setbits_le32(sel_reg, sel_bit);
+	else
+		clrbits_le32(sel_reg, sel_bit);
+}
+
 int board_nand_init(struct nand_chip *nand)
 {
 	uint32_t cfg = 0;
@@ -205,7 +282,7 @@ int board_nand_init(struct nand_chip *nand)
 	nand->IO_ADDR_R = (void *)&nand_reg->nfdata;
 	nand->IO_ADDR_W = (void *)&nand_reg->nfdata;
 
-	nand->select_chip = NULL;
+	nand->select_chip = s3c24x0_nand_select_chip;
 
 	/* read_buf and write_buf are default */
 	/* read_byte and write_byte are default */
@@ -221,6 +298,8 @@ int board_nand_init(struct nand_chip *nand)
 
 	nand->dev_ready = s3c24x0_dev_ready;
 
+	nand->chip_delay = 50;
+
 #ifdef CONFIG_S3C2410_NAND_HWECC
 	nand->ecc.hwctl = s3c24x0_nand_enable_hwecc;
 	nand->ecc.calculate = s3c24x0_nand_calculate_ecc;
-- 
2.0.0.rc2