linux-kernel - [PATCH v2 1/5] mtd: nand: Create a BBT flag to access bad block markers in raw mode

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Date:	Tue, 21 Jul 2015 16:04:42 +0530
From:	Archit Taneja <architt@...eaurora.org>
To:	linux-mtd@...ts.infradead.org, dehrenberg@...gle.com,
	cernekee@...il.com, computersforpeace@...il.com
Cc:	linux-arm-msm@...r.kernel.org, agross@...eaurora.org,
	linux-kernel@...r.kernel.org,
	Archit Taneja <architt@...eaurora.org>
Subject: [PATCH v2 1/5] mtd: nand: Create a BBT flag to access bad block markers in raw mode

Some controllers can access the factory bad block marker from OOB only
when they read it in raw mode. When ECC is enabled, these controllers
discard reading/writing bad block markers, preventing access to them
altogether.

The bbt driver assumes MTD_OPS_PLACE_OOB when scanning for bad blocks.
This results in the nand driver's ecc->read_oob() op to be called, which
works with ECC enabled.

Create a new BBT option flag that tells nand_bbt to force the mode to
MTD_OPS_RAW. This would result in the correct op being called for the
underlying nand controller driver.

Signed-off-by: Archit Taneja <architt@...eaurora.org>
---
 drivers/mtd/nand/nand_base.c | 6 +++++-
 drivers/mtd/nand/nand_bbt.c  | 6 +++++-
 include/linux/mtd/bbm.h      | 7 +++++++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index ceb68ca..0a0c524 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -394,7 +394,11 @@ static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs)
 	} else {
 		ops.len = ops.ooblen = 1;
 	}
-	ops.mode = MTD_OPS_PLACE_OOB;
+
+	if (unlikely(chip->bbt_options & NAND_BBT_ACCESS_BBM_RAW))
+		ops.mode = MTD_OPS_RAW;
+	else
+		ops.mode = MTD_OPS_PLACE_OOB;
 
 	/* Write to first/last page(s) if necessary */
 	if (chip->bbt_options & NAND_BBT_SCANLASTPAGE)
diff --git a/drivers/mtd/nand/nand_bbt.c b/drivers/mtd/nand/nand_bbt.c
index 63a1a36..f2d89c9 100644
--- a/drivers/mtd/nand/nand_bbt.c
+++ b/drivers/mtd/nand/nand_bbt.c
@@ -420,7 +420,11 @@ static int scan_block_fast(struct mtd_info *mtd, struct nand_bbt_descr *bd,
 	ops.oobbuf = buf;
 	ops.ooboffs = 0;
 	ops.datbuf = NULL;
-	ops.mode = MTD_OPS_PLACE_OOB;
+
+	if (unlikely(bd->options & NAND_BBT_ACCESS_BBM_RAW))
+		ops.mode = MTD_OPS_RAW;
+	else
+		ops.mode = MTD_OPS_PLACE_OOB;
 
 	for (j = 0; j < numpages; j++) {
 		/*
diff --git a/include/linux/mtd/bbm.h b/include/linux/mtd/bbm.h
index 36bb6a5..f67f84a 100644
--- a/include/linux/mtd/bbm.h
+++ b/include/linux/mtd/bbm.h
@@ -116,6 +116,13 @@ struct nand_bbt_descr {
 #define NAND_BBT_NO_OOB_BBM	0x00080000
 
 /*
+ * Force MTD_OPS_RAW mode when trying to access bad block markes from OOB. To
+ * be used by controllers which can access BBM only when ECC is disabled, i.e,
+ * when in RAW access mode
+ */
+#define NAND_BBT_ACCESS_BBM_RAW	0x00100000
+
+/*
  * Flag set by nand_create_default_bbt_descr(), marking that the nand_bbt_descr
  * was allocated dynamicaly and must be freed in nand_release(). Has no meaning
  * in nand_chip.bbt_options.
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation

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