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[MTD] [NAND] subpage read feature as a way to increase performance.

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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>
This commit is contained in:
Alexey Korolev 2008-05-15 17:23:18 +01:00 • committed by David Woodhouse
parent ff877ea80e
commit 3d45955962
2 changed files with 91 additions and 1 deletions
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5
include/linux/mtd/nand.h
View file

@ -177,6 +177,7 @@ typedef enum {
#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 @@ struct nand_ecc_ctrl {
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);