[MTD] [NAND] subpage read feature as a way to increase performance.
This patch enables NAND subpage read functionality.
If upper layer drivers are requesting to read non page aligned data NAND
subpage-read functionality reads the only whose ECC regions which include
requested data when original code reads whole page.
This significantly improves performance in many cases.
Here are some digits :
UBI volume mount time
No subpage reads: 5.75 seconds
Subpage read patch: 2.42 seconds
Open/stat time for files on JFFS2 volume:
No subpage read 0m 5.36s
Subpage read 0m 2.88s
Signed-off-by Alexey Korolev <akorolev@infradead.org>
Acked-by: Artem Bityutskiy <dedekind@infradead.org>
Acked-by: Jörn Engel <joern@logfs.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 863e22a..83f6787 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -177,6 +177,7 @@
#define NAND_MUST_PAD(chip) (!(chip->options & NAND_NO_PADDING))
#define NAND_HAS_CACHEPROG(chip) ((chip->options & NAND_CACHEPRG))
#define NAND_HAS_COPYBACK(chip) ((chip->options & NAND_COPYBACK))
+#define NAND_SUBPAGE_READ(chip) ((chip->ecc.mode == NAND_ECC_SOFT))
/* Mask to zero out the chip options, which come from the id table */
#define NAND_CHIPOPTIONS_MSK (0x0000ffff & ~NAND_NO_AUTOINCR)
@@ -274,6 +275,10 @@
int (*read_page)(struct mtd_info *mtd,
struct nand_chip *chip,
uint8_t *buf);
+ int (*read_subpage)(struct mtd_info *mtd,
+ struct nand_chip *chip,
+ uint32_t offs, uint32_t len,
+ uint8_t *buf);
void (*write_page)(struct mtd_info *mtd,
struct nand_chip *chip,
const uint8_t *buf);