Commit 837a6ba4 authored by Gupta, Pekon's avatar Gupta, Pekon Committed by David Woodhouse
Browse files

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: default avatarGupta, Pekon <pekon@ti.com>
Signed-off-by: default avatarArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
parent 4ff6772b

drivers/mtd/nand/cafe_nand.c

+2 −2
Original line number Diff line number Diff line
@@ -530,8 +530,8 @@ static int cafe_nand_write_page_lowlevel(struct mtd_info *mtd, 
}



static int cafe_nand_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 status;

drivers/mtd/nand/lpc32xx_mlc.c

+2 −2
Original line number Diff line number Diff line
@@ -540,8 +540,8 @@ static int lpc32xx_write_page_lowlevel(struct mtd_info *mtd, 
}



static int lpc32xx_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 res;

drivers/mtd/nand/nand_base.c

+86 −13
Original line number Diff line number Diff line
@@ -1110,7 +1110,7 @@ static int nand_read_page_swecc(struct mtd_info *mtd, struct nand_chip *chip, 
}



/**

 * nand_read_subpage - [REPLACEABLE] software ECC based sub-page read function

 * nand_read_subpage - [REPLACEABLE] ECC based sub-page read function

 * @mtd: mtd info structure

 * @chip: nand chip info structure

 * @data_offs: offset of requested data within the page
@@ -1978,6 +1978,67 @@ static int nand_write_page_hwecc(struct mtd_info *mtd, struct nand_chip *chip, 
	return 0;

}





/**

 * nand_write_subpage_hwecc - [REPLACABLE] hardware ECC based subpage write

 * @mtd:	mtd info structure

 * @chip:	nand chip info structure

 * @column:	column address of subpage within the page

 * @data_len:	data length

 * @oob_required: must write chip->oob_poi to OOB

 */

static int nand_write_subpage_hwecc(struct mtd_info *mtd,

				struct nand_chip *chip, uint32_t offset,

				uint32_t data_len, const uint8_t *data_buf,

				int oob_required)

{

	uint8_t *oob_buf  = chip->oob_poi;

	uint8_t *ecc_calc = chip->buffers->ecccalc;

	int ecc_size      = chip->ecc.size;

	int ecc_bytes     = chip->ecc.bytes;

	int ecc_steps     = chip->ecc.steps;

	uint32_t *eccpos  = chip->ecc.layout->eccpos;

	uint32_t start_step = offset / ecc_size;

	uint32_t end_step   = (offset + data_len - 1) / ecc_size;

	int oob_bytes       = mtd->oobsize / ecc_steps;

	int step, i;



	for (step = 0; step < ecc_steps; step++) {

		/* configure controller for WRITE access */

		chip->ecc.hwctl(mtd, NAND_ECC_WRITE);



		/* write data (untouched subpages already masked by 0xFF) */

		chip->write_buf(mtd, data_buf, ecc_size);



		/* mask ECC of un-touched subpages by padding 0xFF */

		if ((step < start_step) || (step > end_step))

			memset(ecc_calc, 0xff, ecc_bytes);

		else

			chip->ecc.calculate(mtd, data_buf, ecc_calc);



		/* mask OOB of un-touched subpages by padding 0xFF */

		/* if oob_required, preserve OOB metadata of written subpage */

		if (!oob_required || (step < start_step) || (step > end_step))

			memset(oob_buf, 0xff, oob_bytes);



		data_buf += ecc_size;

		ecc_calc += ecc_bytes;

		oob_buf  += oob_bytes;

	}



	/* copy calculated ECC for whole page to chip->buffer->oob */

	/* this include masked-value(0xFF) for unwritten subpages */

	ecc_calc = chip->buffers->ecccalc;

	for (i = 0; i < chip->ecc.total; i++)

		chip->oob_poi[eccpos[i]] = ecc_calc[i];



	/* write OOB buffer to NAND device */

	chip->write_buf(mtd, chip->oob_poi, mtd->oobsize);



	return 0;

}





/**

 * nand_write_page_syndrome - [REPLACEABLE] hardware ECC syndrome based page write

 * @mtd: mtd info structure
@@ -2030,6 +2091,8 @@ static int nand_write_page_syndrome(struct mtd_info *mtd, 
 * nand_write_page - [REPLACEABLE] write one page

 * @mtd: MTD device structure

 * @chip: NAND chip descriptor

 * @offset: address offset within the page

 * @data_len: length of actual data to be written

 * @buf: the data to write

 * @oob_required: must write chip->oob_poi to OOB

 * @page: page number to write
@@ -2037,15 +2100,25 @@ static int nand_write_page_syndrome(struct mtd_info *mtd, 
 * @raw: use _raw version of write_page

 */

static int nand_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 status;

	int status, subpage;



	if (!(chip->options & NAND_NO_SUBPAGE_WRITE) &&

		chip->ecc.write_subpage)

		subpage = offset || (data_len < mtd->writesize);

	else

		subpage = 0;



	chip->cmdfunc(mtd, NAND_CMD_SEQIN, 0x00, page);



	if (unlikely(raw))

		status = chip->ecc.write_page_raw(mtd, chip, buf, oob_required);

		status = chip->ecc.write_page_raw(mtd, chip, buf,

							oob_required);

	else if (subpage)

		status = chip->ecc.write_subpage(mtd, chip, offset, data_len,

							 buf, oob_required);

	else

		status = chip->ecc.write_page(mtd, chip, buf, oob_required);
@@ -2159,7 +2232,7 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to, 


	uint8_t *oob = ops->oobbuf;

	uint8_t *buf = ops->datbuf;

	int ret, subpage;

	int ret;

	int oob_required = oob ? 1 : 0;



	ops->retlen = 0;
@@ -2174,10 +2247,6 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to, 
	}



	column = to & (mtd->writesize - 1);

	subpage = column || (writelen & (mtd->writesize - 1));



	if (subpage && oob)

		return -EINVAL;



	chipnr = (int)(to >> chip->chip_shift);

	chip->select_chip(mtd, chipnr);
@@ -2226,9 +2295,9 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to, 
			/* We still need to erase leftover OOB data */

			memset(chip->oob_poi, 0xff, mtd->oobsize);

		}



		ret = chip->write_page(mtd, chip, wbuf, oob_required, page,

				       cached, (ops->mode == MTD_OPS_RAW));

		ret = chip->write_page(mtd, chip, column, bytes, wbuf,

					oob_required, page, cached,

					(ops->mode == MTD_OPS_RAW));

		if (ret)

			break;
@@ -3414,6 +3483,10 @@ int nand_scan_tail(struct mtd_info *mtd) 
			chip->ecc.read_oob = nand_read_oob_std;

		if (!chip->ecc.write_oob)

			chip->ecc.write_oob = nand_write_oob_std;

		if (!chip->ecc.read_subpage)

			chip->ecc.read_subpage = nand_read_subpage;

		if (!chip->ecc.write_subpage)

			chip->ecc.write_subpage = nand_write_subpage_hwecc;



	case NAND_ECC_HW_SYNDROME:

		if ((!chip->ecc.calculate || !chip->ecc.correct ||

include/linux/mtd/nand.h

+6 −2
Original line number Diff line number Diff line
@@ -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,

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