[PATCH] mtd: nand: subpage write support for hardware based ECC schemes
Gupta, Pekon
pekon at ti.com
Wed Mar 27 04:44:56 EDT 2013
Hi,
Can someone please test following patch on non-TI devices ?
I have tested this on Micron NAND using TI-OMAP controller:
MT29F2G08AADWP: 2K/64 (page=2048, subpage=512)
MT29F4G08ABxx: 4K/224 (page=4096, subpage=1024)
(1) using mtd/tests/mtd_subpage.ko
(2) using UBIFS image of different sizes
(attaching a generic script to create UBIFS image.)
(3) using loosely written nand-raw test, which writes in multiples of
subpage lengths
But due to un-availability I couldn't test it on other boards.
So, any ACKs | NAKs will help to improve this further.
with regards, pekon
> From: "Gupta, Pekon" <pekon at ti.com>
>
> 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.
>
> Signed-off-by: Gupta, Pekon <pekon at ti.com>
> ---
> drivers/mtd/nand/nand_base.c | 99
> ++++++++++++++++++++++++++++++++++++++------
> include/linux/mtd/nand.h | 8 +++-
> 2 files changed, 92 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/mtd/nand/nand_base.c
> b/drivers/mtd/nand/nand_base.c
> index 4321415..5138b6b 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -1127,7 +1127,7 @@ 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
> @@ -1979,6 +1979,67 @@ 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
> @@ -2031,6 +2092,8 @@ 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
> @@ -2038,15 +2101,25 @@ 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);
>
> @@ -2160,7 +2233,7 @@ 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;
> @@ -2175,10 +2248,6 @@ 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);
> @@ -2227,9 +2296,9 @@ 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;
>
> @@ -3458,6 +3527,10 @@ 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 ||
> diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
> index 7ccb3c5..7d81403f 100644
> --- a/include/linux/mtd/nand.h
> +++ b/include/linux/mtd/nand.h
> @@ -354,6 +354,7 @@ 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
> @@ -385,6 +386,9 @@ 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,
> @@ -520,8 +524,8 @@ 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,
> --
> 1.8.1
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