[V3, 2/2] mtd: brcmnand: Detect sticky ucorr ecc error on dma reads

Kamal Dasu
2016-06-09T21:18:40Z

This change provides a fix for controller bug where nand
controller could have a possible sticky error after a PIO
followed by a DMA read. The fix retries a read if we see
a uncorr_ecc after read to detect such sticky errors.
The fix applies to only controller version 7.0 and 7.1.

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
---
V3 changes
none
V2 Changes
Restrict controller bug workaround to version 7.0 and 7.1
---
drivers/mtd/nand/brcmnand/brcmnand.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c
index 7ee9617..1156495 100644
--- a/drivers/mtd/nand/brcmnand/brcmnand.c
+++ b/drivers/mtd/nand/brcmnand/brcmnand.c
@@ -1602,9 +1602,11 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
struct brcmnand_controller *ctrl = host->ctrl;
u64 err_addr = 0;
int err;
+ static bool retry = true;

dev_dbg(ctrl->dev, "read %llx -> %p\n", (unsigned long long)addr, buf);

+try_dmaread:
brcmnand_write_reg(ctrl, BRCMNAND_UNCORR_COUNT, 0);

if (has_flash_dma(ctrl) && !oob && flash_dma_buf_ok(buf)) {
@@ -1626,6 +1628,22 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,

if (mtd_is_eccerr(err)) {
/*
+ * On controller version and 7.0, 7.1 , DMA read after a
+ * prior PIO read that reported uncorrectable error,
+ * the DMA engine captures this error following DMA read
+ * cleared only on subsequent DMA read, so just retry once
+ * to clear a possible false error reported for current DMA
+ * read
+ */
+ if ((ctrl->nand_version == 0x0700) ||
+ (ctrl->nand_version == 0x0701)) {
+ if (retry) {
+ retry = false;
+ goto try_dmaread;
+ }
+ }
+
+ /*
* Controller version 7.2 has hw encoder to detect erased page
* bitflips, apply sw verification for older controllers only
*/
--
1.9.1