Commit ea3b2ea2 authored Jun 08, 2012 by Shmulik Ladkani Committed by David Woodhouse Jun 09, 2012

mtd: nand: initialize bitflip_threshold prior to BBT scanning



As of edbc4540 [mtd: driver _read() returns max_bitflips; mtd_read()
returns -EUCLEAN], 'mtd->bitflip_threshold' must be set for mtd devices
having ECC, prior any 'mtd_read()' call.
Otherwise, 'mtd_read()' will falsely return -EUCLEAN.

Normally, 'mtd->bitflip_threshold' is initialized when the MTD is added.

However, this is too late for NAND MTDs, as 'scan_bbt()' is invoked
prior the existing initialization of 'mtd->bitflip_threshold'.

This is a problem since 'scan_bbt()' calls 'mtd_read()', in the case
of a flash-based bad block table.
It resulted in a falsely reported bitflips indication during BBT read,
which lead to constant scrubbing of the flash BBT blocks.

Initialize 'mtd->bitflip_threshold' to its default value (if not already
set by the driver), prior to invocation of 'scan_bbt()'.

Reported-by: Sascha Hauer <s.hauer@pengutronix.de>
Tested-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

parent cfaf0251

drivers/mtd/nand/nand_base.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -3501,6 +3501,13 @@ int nand_scan_tail(struct mtd_info *mtd)
		/* propagate ecc info to mtd_info */
		mtd->ecclayout = chip->ecc.layout;
		mtd->ecc_strength = chip->ecc.strength;
		/*
		* Initialize bitflip_threshold to its default prior scan_bbt() call.
		* scan_bbt() might invoke mtd_read(), thus bitflip_threshold must be
		* properly set.
		*/
		if (!mtd->bitflip_threshold)
		mtd->bitflip_threshold = mtd->ecc_strength;

		/* Check, if we should skip the bad block table scan */
		if (chip->options & NAND_SKIP_BBTSCAN)