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* [PATCH] mtd: nand_omap_gpmc: fix BCH error correction
@ 2017-04-14 18:32 Matt Reimer
  2017-04-19  8:10 ` Sascha Hauer
  2017-05-26 12:28 ` Daniel Schultz
  0 siblings, 2 replies; 4+ messages in thread
From: Matt Reimer @ 2017-04-14 18:32 UTC (permalink / raw)
  To: barebox; +Cc: Matt Reimer

BCH error detection and correction was only looking at the first
of four syndrome polynomials, which meant it was failing to detect
and correct bitflips in the last 3/4 of the data. In effect, only
the first 512 bytes of a 2048 byte page were being protected by ECC.

The syndrome polynomials (BCH error codes) are stored in the NAND's
OOB, each of which protects 512 bytes of data. The driver used
eccsteps = 1 which effectively made it only use the first polynomial,
and therefore was only protecting the first 512 bytes of the page.

The fix is to pull over a bit of code from the kernel's
omap_correct_data() that sets eccsteps = 4 when the page size is 2048
bytes and hardware ECC is being used.

Signed-off-by: Matt Reimer <mreimer@sdgsystems.com>
---
 drivers/mtd/nand/nand_omap_gpmc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/nand_omap_gpmc.c b/drivers/mtd/nand/nand_omap_gpmc.c
index 9d9d27e..2fe6a10 100644
--- a/drivers/mtd/nand/nand_omap_gpmc.c
+++ b/drivers/mtd/nand/nand_omap_gpmc.c
@@ -302,7 +302,8 @@ static int omap_correct_bch(struct mtd_info *mtd, uint8_t *dat,
 	unsigned int err_loc[8];
 	int select_4_8;
 
-	int eccsteps = oinfo->nand.ecc.steps;
+        int eccsteps = (nand->ecc.mode == NAND_ECC_HW) &&
+                (nand->ecc.size == 2048) ? 4 : 1;
 	int eccsize = oinfo->nand.ecc.bytes;
 
 	switch (oinfo->ecc_mode) {
-- 
2.10.1


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^ permalink raw reply	[flat|nested] 4+ messages in thread
* [PATCH] mtd: nand_omap_gpmc: fix BCH error correction
@ 2017-04-14 18:29 Matt Reimer
  0 siblings, 0 replies; 4+ messages in thread
From: Matt Reimer @ 2017-04-14 18:29 UTC (permalink / raw)
  To: barebox; +Cc: Matt Reimer

BCH error detection and correction was only looking at the first
of four syndrome polynomials, which meant it was failing to detect
and correct bitflips in the last 3/4 of the data. In effect, only
the first 512 bytes of a 2048 byte page were being protected by ECC.

The syndrome polynomials (BCH error codes) are stored in the NAND's
OOB, each of which protects 512 bytes of data. The driver used
eccsteps = 1 which effectively made it only use the first polynomial,
and therefore was only protecting the first 512 bytes of the page.

The fix is to pull over a bit of code from the kernel's
omap_correct_data() that sets eccsteps = 4 when the page size is 2048
bytes and hardware ECC is being used.

Signed-off-by: Matt Reimer <mreimer@sdgsystems.com>
---
 drivers/mtd/nand/nand_omap_gpmc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/nand_omap_gpmc.c b/drivers/mtd/nand/nand_omap_gpmc.c
index 9d9d27e..2fe6a10 100644
--- a/drivers/mtd/nand/nand_omap_gpmc.c
+++ b/drivers/mtd/nand/nand_omap_gpmc.c
@@ -302,7 +302,8 @@ static int omap_correct_bch(struct mtd_info *mtd, uint8_t *dat,
 	unsigned int err_loc[8];
 	int select_4_8;
 
-	int eccsteps = oinfo->nand.ecc.steps;
+        int eccsteps = (nand->ecc.mode == NAND_ECC_HW) &&
+                (nand->ecc.size == 2048) ? 4 : 1;
 	int eccsize = oinfo->nand.ecc.bytes;
 
 	switch (oinfo->ecc_mode) {
-- 
2.10.1


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^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2017-05-26 12:28 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2017-04-14 18:32 [PATCH] mtd: nand_omap_gpmc: fix BCH error correction Matt Reimer
2017-04-19  8:10 ` Sascha Hauer
2017-05-26 12:28 ` Daniel Schultz
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2017-04-14 18:29 Matt Reimer

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