openwrtv4/target/linux/ipq806x/patches-4.4/161-mtd-nand-Create-a-BBT-flag-to-access-bad-block-markers-in-raw-mode.patch

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Subject: [v3,
	1/5] mtd: nand: Create a BBT flag to access bad block markers in raw
	mode
From: Archit Taneja <architt@codeaurora.org>
X-Patchwork-Id: 6927081
Message-Id: <1438578498-32254-2-git-send-email-architt@codeaurora.org>
To: linux-mtd@lists.infradead.org, dehrenberg@google.com,
	cernekee@gmail.com, computersforpeace@gmail.com
Cc: linux-arm-msm@vger.kernel.org, agross@codeaurora.org,
	sboyd@codeaurora.org, linux-kernel@vger.kernel.org,
	Archit Taneja <architt@codeaurora.org>
Date: Mon,  3 Aug 2015 10:38:14 +0530

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.

Reviewed-by: Andy Gross <agross@codeaurora.org>
Signed-off-by: Archit Taneja <architt@codeaurora.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(-)

--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -394,7 +394,11 @@
 	} 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)
--- a/drivers/mtd/nand/nand_bbt.c
+++ b/drivers/mtd/nand/nand_bbt.c
@@ -420,7 +420,11 @@
 	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++) {
 		/*
--- a/include/linux/mtd/bbm.h
+++ b/include/linux/mtd/bbm.h
@@ -116,6 +116,12 @@
 #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.