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authorPeng Fan <peng.fan@nxp.com>2016-05-06 12:13:38 +0800
committerYe Li <ye.li@nxp.com>2017-04-05 14:04:27 +0800
commit026751697e41c7376414a8716cf0ea4bf998b85f (patch)
tree91acb01c97a1c846f484da9ab0fcfb6684e57eef
parent58794b3ebefea468bb1c57184b79df500f427927 (diff)
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MLK-12693-1 nand: mxs: fix the bitflips for erased page when uncorrectable error
This patch is porting from linux: http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/commit/?h=imx_4.1.15_1.0.0_ga&id=3d42fcece496224fde59f9343763fb2dfc5b0768 " We may meet the bitflips in reading an erased page(contains all 0xFF), this may causes the UBIFS corrupt, please see the log from Elie: ----------------------------------------------------------------- [ 3.831323] UBI warning: ubi_io_read: error -74 (ECC error) while reading 16384 bytes from PEB 443:245760, read only 16384 bytes, retry [ 3.845026] UBI warning: ubi_io_read: error -74 (ECC error) while reading 16384 bytes from PEB 443:245760, read only 16384 bytes, retry [ 3.858710] UBI warning: ubi_io_read: error -74 (ECC error) while reading 16384 bytes from PEB 443:245760, read only 16384 bytes, retry [ 3.872408] UBI error: ubi_io_read: error -74 (ECC error) while reading 16384 bytes from PEB 443:245760, read 16384 bytes ... [ 4.011529] UBIFS error (pid 36): ubifs_recover_leb: corrupt empty space LEB 27:237568, corruption starts at 9815 [ 4.021897] UBIFS error (pid 36): ubifs_scanned_corruption: corruption at LEB 27:247383 [ 4.030000] UBIFS error (pid 36): ubifs_scanned_corruption: first 6569 bytes from LEB 27:247383 ----------------------------------------------------------------- This patch does a check for the uncorrectable failure in the following steps: [0] set the threshold. The threshold is set based on the truth: "A single 0 bit will lead to gf_len(13 or 14) bits 0 after the BCH do the ECC." For the sake of safe, we will set the threshold with half the gf_len, and do not make it bigger the ECC strength. [1] count the bitflips of the current ECC chunk, assume it is N. [2] if the (N <= threshold) is true, we continue to read out the page with ECC disabled. and we count the bitflips again, assume it is N2. (We read out the whole page, not just a chunk, this makes the check more strictly, and make the code more simple.) [3] if the (N2 <= threshold) is true again, we can regard this is a erased page. This is because a real erased page is full of 0xFF(maybe also has several bitflips), while a page contains the 0xFF data will definitely has many bitflips in the ECC parity areas. [4] if the [3] fails, we can regard this is a page filled with the '0xFF' data. " Signed-off-by: Peng Fan <peng.fan@nxp.com> (cherry picked from commit ceb324a2914487aa517a6c70a06a20b5e3438fda)
-rw-r--r--drivers/mtd/nand/mxs_nand.c44
1 files changed, 44 insertions, 0 deletions
diff --git a/drivers/mtd/nand/mxs_nand.c b/drivers/mtd/nand/mxs_nand.c
index 22ba85e..7b1e475 100644
--- a/drivers/mtd/nand/mxs_nand.c
+++ b/drivers/mtd/nand/mxs_nand.c
@@ -645,6 +645,45 @@ static uint8_t mxs_nand_read_byte(struct mtd_info *mtd)
return buf;
}
+static bool mxs_nand_erased_page(struct mtd_info *mtd, struct nand_chip *nand,
+ uint8_t *buf, int chunk, int page)
+{
+ int gf_len = galois_field;
+ unsigned int flip_bits = 0, flip_bits_noecc = 0;
+ unsigned int threshold;
+ unsigned int ecc_chunkn_size = MXS_NAND_CHUNK_DATA_CHUNK_SIZE;
+ unsigned int base = ecc_chunkn_size * chunk;
+ uint32_t *dma_buf = (uint32_t *)buf;
+ int i;
+
+ threshold = gf_len / 2;
+ if (threshold > ecc_strength)
+ threshold = ecc_strength;
+
+ for (i = 0; i < ecc_chunkn_size; i++) {
+ flip_bits += hweight8(~buf[base + i]);
+ if (flip_bits > threshold)
+ return false;
+ }
+
+ nand->cmdfunc(mtd, NAND_CMD_READ0, 0, page);
+ nand->read_buf(mtd, buf, mtd->writesize);
+
+ for (i = 0; i < mtd->writesize / 4; i++) {
+ flip_bits_noecc += hweight32(~dma_buf[i]);
+ if (flip_bits_noecc > threshold)
+ return false;
+ }
+
+ mtd->ecc_stats.corrected += flip_bits;
+
+ memset(buf, 0xff, mtd->writesize);
+
+ printf("The page(%d) is an erased page(%d,%d,%d,%d).\n", page, chunk, threshold, flip_bits, flip_bits_noecc);
+
+ return true;
+}
+
/*
* Read a page from NAND.
*/
@@ -747,6 +786,8 @@ static int mxs_nand_ecc_read_page(struct mtd_info *mtd, struct nand_chip *nand,
goto rtn;
}
+ mxs_nand_return_dma_descs(nand_info);
+
/* Invalidate caches */
mxs_nand_inval_data_buf(nand_info);
@@ -763,6 +804,9 @@ static int mxs_nand_ecc_read_page(struct mtd_info *mtd, struct nand_chip *nand,
continue;
if (status[i] == 0xfe) {
+ if (mxs_nand_erased_page(mtd, nand,
+ nand_info->data_buf, i, page))
+ break;
failed++;
continue;
}