mtd: nand: subpage write support for hardware based ECC schemes

This patch adds support for subpage (partial-page) writes when using
hardware based ECC schemes.
Advantages:
(1) reduces storage overhead when using file-systems like UBIFS, which
store LEB header at page-size granularity.
(2) allows independent subpage writes, thereby increasing NAND storage
efficiency for non-page aligned data.
+ updated cafe_nand and lpc32xx_mlc NAND drivers for change in
chip->write_page interface.

Signed-off-by: Gupta, Pekon <pekon@ti.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index ebf970e11428..ab6363443ce8 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -318,6 +318,7 @@ struct nand_hw_control {
  *              any single ECC step, 0 if bitflips uncorrectable, -EIO hw error
  * @read_subpage:       function to read parts of the page covered by ECC;
  *                      returns same as read_page()
+ * @write_subpage:      function to write 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
@@ -349,6 +350,9 @@ struct nand_ecc_ctrl {
                         uint8_t *buf, int oob_required, int page);
         int (*read_subpage)(struct mtd_info *mtd, struct nand_chip *chip,
                         uint32_t offs, uint32_t len, uint8_t *buf);
+        int (*write_subpage)(struct mtd_info *mtd, struct nand_chip *chip,
+                        uint32_t offset, uint32_t data_len,
+                        const uint8_t *data_buf, int oob_required);
         int (*write_page)(struct mtd_info *mtd, struct nand_chip *chip,
                         const uint8_t *buf, int oob_required);
         int (*write_oob_raw)(struct mtd_info *mtd, struct nand_chip *chip,
@@ -484,8 +488,8 @@ struct nand_chip {
         int (*errstat)(struct mtd_info *mtd, struct nand_chip *this, int state,
                         int status, int page);
         int (*write_page)(struct mtd_info *mtd, struct nand_chip *chip,
-                        const uint8_t *buf, int oob_required, int page,
-                        int cached, int raw);
+                        uint32_t offset, int data_len, const uint8_t *buf,
+                        int oob_required, int page, int cached, int raw);
         int (*onfi_set_features)(struct mtd_info *mtd, struct nand_chip *chip,
                         int feature_addr, uint8_t *subfeature_para);
         int (*onfi_get_features)(struct mtd_info *mtd, struct nand_chip *chip,