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mtd: brcmnand: Add check for erased page bitflips 

Check for erased page bitflips in a page. And if well within
threshold return data as all 0xff. Apply sw check for controller
version < 7.2. Controller vesion >= 7.2 has hw support.

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
This commit is contained in:
Kamal Dasu 2016-06-09 17:17:54 -04:00 committed by Boris Brezillon
parent 1c7fe6b438
commit 02b88eea9f
1 changed files with 62 additions and 0 deletions
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62
drivers/mtd/nand/brcmnand/brcmnand.c
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@ -1602,6 +1602,56 @@ static int brcmnand_read_by_pio(struct mtd_info *mtd, struct nand_chip *chip,
return ret;
}
/*
* Check a page to see if it is erased (w/ bitflips) after an uncorrectable ECC
* error
*
* Because the HW ECC signals an ECC error if an erase paged has even a single
* bitflip, we must check each ECC error to see if it is actually an erased
* page with bitflips, not a truly corrupted page.
*
* On a real error, return a negative error code (-EBADMSG for ECC error), and
* buf will contain raw data.
* Otherwise, buf gets filled with 0xffs and return the maximum number of
* bitflips-per-ECC-sector to the caller.
*
*/
static int brcmstb_nand_verify_erased_page(struct mtd_info *mtd,
struct nand_chip *chip, void *buf, u64 addr)
{
int i, sas;
void *oob = chip->oob_poi;
int bitflips = 0;
int page = addr >> chip->page_shift;
int ret;
if (!buf) {
buf = chip->buffers->databuf;
/* Invalidate page cache */
chip->pagebuf = -1;
}
sas = mtd->oobsize / chip->ecc.steps;
/* read without ecc for verification */
chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);
ret = chip->ecc.read_page_raw(mtd, chip, buf, true, page);
if (ret)
return ret;
for (i = 0; i < chip->ecc.steps; i++, oob += sas) {
ret = nand_check_erased_ecc_chunk(buf, chip->ecc.size,
oob, sas, NULL, 0,
chip->ecc.strength);
if (ret < 0)
return ret;
bitflips = max(bitflips, ret);
}
return bitflips;
}
static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
u64 addr, unsigned int trans, u32 *buf, u8 *oob)
{
@ -1632,6 +1682,18 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
}
if (mtd_is_eccerr(err)) {
/*
* Controller version 7.2 has hw encoder to detect erased page
* bitflips, apply sw verification for older controllers only
*/
if (ctrl->nand_version < 0x0702) {
err = brcmstb_nand_verify_erased_page(mtd, chip, buf,
addr);
/* erased page bitflips corrected */
if (err > 0)
return err;
}
dev_dbg(ctrl->dev, "uncorrectable error at 0x%llx\n",
(unsigned long long)err_addr);
mtd->ecc_stats.failed++;