[PATCH] mtd: nand: subpage write support for hardware based ECC schemes
Gupta, Pekon
pekon at ti.com
Fri Mar 15 08:59:38 EDT 2013
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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