[patch 3/3] mtd-nand: DaVinci: Add 4-bit ECC support for large page NAND chips

akpm
2009-08-07T18:25:35Z

From: Sneha Narnakaje <nsnehaprabha@ti.com>

This patch adds 4-bit ECC support for large page NAND chips using the new
ECC mode NAND_ECC_HW_OOB_FIRST. The platform data from board-dm355-evm
has been adjusted to use this mode.

The patches have been verified on DM355 device with 2K Micron devices
using mtd-tests and JFFS2. Error correction upto 4-bits has also been
verified using nandwrite/nanddump utilities.

Reviewed-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Sneha Narnakaje <nsnehaprabha@ti.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

drivers/mtd/nand/davinci_nand.c | 45 ++++++++++++++++++++++++++----
1 file changed, 39 insertions(+), 6 deletions(-)

diff -puN drivers/mtd/nand/davinci_nand.c~mtd-nand-davinci-add-4-bit-ecc-support-for-large-page-nand-chips drivers/mtd/nand/davinci_nand.c
--- a/drivers/mtd/nand/davinci_nand.c~mtd-nand-davinci-add-4-bit-ecc-support-for-large-page-nand-chips
+++ a/drivers/mtd/nand/davinci_nand.c
@@ -348,6 +348,12 @@ compare:
if (!(syndrome[0] | syndrome[1] | syndrome[2] | syndrome[3]))
return 0;

+ /*
+ * Clear any previous address calculation by doing a dummy read of an
+ * error address register.
+ */
+ davinci_nand_readl(info, NAND_ERR_ADD1_OFFSET);
+
/* Start address calculation, and wait for it to complete.
* We _could_ start reading more data while this is working,
* to speed up the overall page read.
@@ -359,8 +365,10 @@ compare:

switch ((fsr >> 8) & 0x0f) {
case 0: /* no error, should not happen */
+ davinci_nand_readl(info, NAND_ERR_ERRVAL1_OFFSET);
return 0;
case 1: /* five or more errors detected */
+ davinci_nand_readl(info, NAND_ERR_ERRVAL1_OFFSET);
return -EIO;
case 2: /* error addresses computed */
case 3:
@@ -500,6 +508,26 @@ static struct nand_ecclayout hwecc4_smal
},
};

+/* An ECC layout for using 4-bit ECC with large-page (2048bytes) flash,
+ * storing ten ECC bytes plus the manufacturer's bad block marker byte,
+ * and not overlapping the default BBT markers.
+ */
+static struct nand_ecclayout hwecc4_2048 __initconst = {
+ .eccbytes = 40,
+ .eccpos = {
+ /* at the end of spare sector */
+ 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,
+ 34, 35, 36, 37, 38, 39, 40, 41, 42, 43,
+ 44, 45, 46, 47, 48, 49, 50, 51, 52, 53,
+ 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
+ },
+ .oobfree = {
+ /* 1 byte at offset 0 holds manufacturer badblock marker */
+ {.offset = 1, .length = 23, },
+ /* 5 bytes at offset 8 hold BBT markers */
+ /* 8 bytes at offset 16 hold JFFS2 clean markers */
+ },
+};

static int __init nand_davinci_probe(struct platform_device *pdev)
{
@@ -690,15 +718,20 @@ static int __init nand_davinci_probe(str
info->mtd.oobsize - 16;
goto syndrome_done;
}
+ if (chunks == 4) {
+ info->ecclayout = hwecc4_2048;
+ info->chip.ecc.mode = NAND_ECC_HW_OOB_FIRST;
+ goto syndrome_done;
+ }

- /* For large page chips we'll be wanting to use a
- * not-yet-implemented mode that reads OOB data
- * before reading the body of the page, to avoid
- * the "infix OOB" model of NAND_ECC_HW_SYNDROME
- * (and preserve manufacturer badblock markings).
+ /* 4K page chips are not yet supported. The eccpos from
+ * nand_ecclayout cannot hold 80 bytes and change to eccpos[]
+ * breaks userspace ioctl interface with mtd-utils. Once we
+ * resolve this issue, NAND_ECC_HW_OOB_FIRST mode can be used
+ * for the 4K page chips.
*/
dev_warn(&pdev->dev, "no 4-bit ECC support yet "
- "for large page NAND\n");
+ "for 4K page NAND\n");
ret = -EIO;
goto err_scan;

_