mtd: support writing OOB without ECC

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=9ce244b3fb416ce6600e05612ac46b9692dcc638
Commit:     9ce244b3fb416ce6600e05612ac46b9692dcc638
Parent:     10a2bcae99267b28e058b089fda30de7397b69f5
Author:     Brian Norris <computersforpeace at gmail.com>
AuthorDate: Tue Aug 30 18:45:37 2011 -0700
Committer:  Artem Bityutskiy <artem.bityutskiy at intel.com>
CommitDate: Sun Sep 11 15:02:18 2011 +0300

    mtd: support writing OOB without ECC
    
    This fixes issues with `nandwrite -n -o' and the MEMWRITEOOB[64] ioctls
    on hardware that writes ECC when writing OOB. The problem arises as
    follows: `nandwrite -n' can write page data to flash without applying
    ECC, but when used with the `-o' option, ECC is applied (incorrectly),
    contrary to the `--noecc' option.
    
    I found that this is the case because my hardware computes and writes
    ECC data to flash upon either OOB write or page write. Thus, to support
    a proper "no ECC" write, my driver must know when we're performing a raw
    OOB write vs. a normal ECC OOB write. However, MTD does not pass any raw
    mode information to the write_oob functions.  This patch addresses the
    problems by:
    
    1) Passing MTD_OOB_RAW down to lower layers, instead of just defaulting
       to MTD_OOB_PLACE
    2) Handling MTD_OOB_RAW within the NAND layer's `nand_do_write_oob'
    3) Adding a new (replaceable) function pointer in struct ecc_ctrl; this
       function should support writing OOB without ECC data. Current
       hardware often can use the same OOB write function when writing
       either with or without ECC
    
    This was tested with nandsim as well as on actual SLC NAND.
    
    Signed-off-by: Brian Norris <computersforpeace at gmail.com>
    Cc: Jim Quinlan <jim2101024 at gmail.com>
    Signed-off-by: Artem Bityutskiy <artem.bityutskiy at intel.com>
---
 drivers/mtd/mtdchar.c        |    3 ++-
 drivers/mtd/nand/nand_base.c |   10 +++++++++-
 include/linux/mtd/nand.h     |    3 +++
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index b206254..bcb7f05 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -391,6 +391,7 @@ static int mtd_do_writeoob(struct file *file, struct mtd_info *mtd,
 	uint64_t start, uint32_t length, void __user *ptr,
 	uint32_t __user *retp)
 {
+	struct mtd_file_info *mfi = file->private_data;
 	struct mtd_oob_ops ops;
 	uint32_t retlen;
 	int ret = 0;
@@ -412,7 +413,7 @@ static int mtd_do_writeoob(struct file *file, struct mtd_info *mtd,
 	ops.ooblen = length;
 	ops.ooboffs = start & (mtd->writesize - 1);
 	ops.datbuf = NULL;
-	ops.mode = MTD_OOB_PLACE;
+	ops.mode = (mfi->mode == MTD_MODE_RAW) ? MTD_OOB_RAW : MTD_OOB_PLACE;
 
 	if (ops.ooboffs && ops.ooblen > (mtd->oobsize - ops.ooboffs))
 		return -EINVAL;
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 7f2691f..b61a7c7 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -2404,7 +2404,11 @@ static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
 		chip->pagebuf = -1;
 
 	nand_fill_oob(mtd, ops->oobbuf, ops->ooblen, ops);
-	status = chip->ecc.write_oob(mtd, chip, page & chip->pagemask);
+
+	if (ops->mode == MTD_OOB_RAW)
+		status = chip->ecc.write_oob_raw(mtd, chip, page & chip->pagemask);
+	else
+		status = chip->ecc.write_oob(mtd, chip, page & chip->pagemask);
 
 	if (status)
 		return status;
@@ -3380,6 +3384,10 @@ int nand_scan_tail(struct mtd_info *mtd)
 		BUG();
 	}
 
+	/* For many systems, the standard OOB write also works for raw */
+	if (!chip->ecc.write_oob_raw)
+		chip->ecc.write_oob_raw = chip->ecc.write_oob;
+
 	/*
 	 * The number of bytes available for a client to place data into
 	 * the out of band area.
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 85fef68..5f3fdd9 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -340,6 +340,7 @@ struct nand_hw_control {
  * @read_subpage:	function to read parts of the page covered by ECC.
  * @write_page:	function to write a page according to the ECC generator
  *		requirements.
+ * @write_oob_raw:	function to write chip OOB data without ECC
  * @read_oob:	function to read chip OOB data
  * @write_oob:	function to write chip OOB data
  */
@@ -368,6 +369,8 @@ struct nand_ecc_ctrl {
 			uint32_t offs, uint32_t len, uint8_t *buf);
 	void (*write_page)(struct mtd_info *mtd, struct nand_chip *chip,
 			const uint8_t *buf);
+	int (*write_oob_raw)(struct mtd_info *mtd, struct nand_chip *chip,
+			int page);
 	int (*read_oob)(struct mtd_info *mtd, struct nand_chip *chip, int page,
 			int sndcmd);
 	int (*write_oob)(struct mtd_info *mtd, struct nand_chip *chip,