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authorAlexey Korolev <akorolev@infradead.org>2008-05-15 17:23:18 +0100
committerDavid Woodhouse <David.Woodhouse@intel.com>2008-07-25 10:49:50 -0400
commit3d45955962496879dead8d4dd70bb9a23b07154b (patch)
treeaf34201ba3bfc195a22ceac43a1c22f2f7c2fbe8 /drivers/mtd/nand
parentff877ea80efa2015b6263766f78ee42c2a1b32f9 (diff)
[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>
Diffstat (limited to 'drivers/mtd/nand')
-rw-r--r--drivers/mtd/nand/nand_base.c87
1 files changed, 86 insertions, 1 deletions
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index ba1bdf78732..d1129bae6c2 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -798,6 +798,87 @@ static int nand_read_page_swecc(struct mtd_info *mtd, struct nand_chip *chip,
}
/**
+ * nand_read_subpage - [REPLACABLE] software ecc based sub-page read function
+ * @mtd: mtd info structure
+ * @chip: nand chip info structure
+ * @dataofs offset of requested data within the page
+ * @readlen data length
+ * @buf: buffer to store read data
+ */
+static int nand_read_subpage(struct mtd_info *mtd, struct nand_chip *chip, uint32_t data_offs, uint32_t readlen, uint8_t *bufpoi)
+{
+ int start_step, end_step, num_steps;
+ uint32_t *eccpos = chip->ecc.layout->eccpos;
+ uint8_t *p;
+ int data_col_addr, i, gaps = 0;
+ int datafrag_len, eccfrag_len, aligned_len, aligned_pos;
+ int busw = (chip->options & NAND_BUSWIDTH_16) ? 2 : 1;
+
+ /* Column address wihin the page aligned to ECC size (256bytes). */
+ start_step = data_offs / chip->ecc.size;
+ end_step = (data_offs + readlen - 1) / chip->ecc.size;
+ num_steps = end_step - start_step + 1;
+
+ /* Data size aligned to ECC ecc.size*/
+ datafrag_len = num_steps * chip->ecc.size;
+ eccfrag_len = num_steps * chip->ecc.bytes;
+
+ data_col_addr = start_step * chip->ecc.size;
+ /* If we read not a page aligned data */
+ if (data_col_addr != 0)
+ chip->cmdfunc(mtd, NAND_CMD_RNDOUT, data_col_addr, -1);
+
+ p = bufpoi + data_col_addr;
+ chip->read_buf(mtd, p, datafrag_len);
+
+ /* Calculate ECC */
+ for (i = 0; i < eccfrag_len ; i += chip->ecc.bytes, p += chip->ecc.size)
+ chip->ecc.calculate(mtd, p, &chip->buffers->ecccalc[i]);
+
+ /* The performance is faster if to position offsets
+ according to ecc.pos. Let make sure here that
+ there are no gaps in ecc positions */
+ for (i = 0; i < eccfrag_len - 1; i++) {
+ if (eccpos[i + start_step * chip->ecc.bytes] + 1 !=
+ eccpos[i + start_step * chip->ecc.bytes + 1]) {
+ gaps = 1;
+ break;
+ }
+ }
+ if (gaps) {
+ chip->cmdfunc(mtd, NAND_CMD_RNDOUT, mtd->writesize, -1);
+ chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
+ } else {
+ /* send the command to read the particular ecc bytes */
+ /* take care about buswidth alignment in read_buf */
+ aligned_pos = eccpos[start_step * chip->ecc.bytes] & ~(busw - 1);
+ aligned_len = eccfrag_len;
+ if (eccpos[start_step * chip->ecc.bytes] & (busw - 1))
+ aligned_len++;
+ if (eccpos[(start_step + num_steps) * chip->ecc.bytes] & (busw - 1))
+ aligned_len++;
+
+ chip->cmdfunc(mtd, NAND_CMD_RNDOUT, mtd->writesize + aligned_pos, -1);
+ chip->read_buf(mtd, &chip->oob_poi[aligned_pos], aligned_len);
+ }
+
+ for (i = 0; i < eccfrag_len; i++)
+ chip->buffers->ecccode[i] = chip->oob_poi[eccpos[i + start_step * chip->ecc.bytes]];
+
+ p = bufpoi + data_col_addr;
+ for (i = 0; i < eccfrag_len ; i += chip->ecc.bytes, p += chip->ecc.size) {
+ int stat;
+
+ stat = chip->ecc.correct(mtd, p, &chip->buffers->ecccode[i], &chip->buffers->ecccalc[i]);
+ if (stat == -1)
+ mtd->ecc_stats.failed++;
+ else
+ mtd->ecc_stats.corrected += stat;
+ }
+ return 0;
+}
+
+/**
* nand_read_page_hwecc - [REPLACABLE] hardware ecc based page read function
* @mtd: mtd info structure
* @chip: nand chip info structure
@@ -994,6 +1075,8 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
/* Now read the page into the buffer */
if (unlikely(ops->mode == MTD_OOB_RAW))
ret = chip->ecc.read_page_raw(mtd, chip, bufpoi);
+ else if (!aligned && NAND_SUBPAGE_READ(chip) && !oob)
+ ret = chip->ecc.read_subpage(mtd, chip, col, bytes, bufpoi);
else
ret = chip->ecc.read_page(mtd, chip, bufpoi);
if (ret < 0)
@@ -1001,7 +1084,8 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
/* Transfer not aligned data */
if (!aligned) {
- chip->pagebuf = realpage;
+ if (!NAND_SUBPAGE_READ(chip) && !oob)
+ chip->pagebuf = realpage;
memcpy(buf, chip->buffers->databuf + col, bytes);
}
@@ -2521,6 +2605,7 @@ int nand_scan_tail(struct mtd_info *mtd)
chip->ecc.calculate = nand_calculate_ecc;
chip->ecc.correct = nand_correct_data;
chip->ecc.read_page = nand_read_page_swecc;
+ chip->ecc.read_subpage = nand_read_subpage;
chip->ecc.write_page = nand_write_page_swecc;
chip->ecc.read_oob = nand_read_oob_std;
chip->ecc.write_oob = nand_write_oob_std;