openwrt-xburst/target/linux/xburst/patches-2.6.32/904-NAND-Optimize-reading-the-eec-data-for-the-JZ4740-ev.patch

From 3eeeee7302a9b25de1eeabd901d3bb678d9983d9 Mon Sep 17 00:00:00 2001
From: Lars-Peter Clausen <lars@metafoo.de>
Date: Sat, 26 Feb 2011 15:32:30 +0100
Subject: [PATCH 4/4] NAND: Optimize reading the eec data for the JZ4740 (evil hack)

We know that the ecc data is continuous, this allows us to only read the ecc
data instead of the whole oob section, which slightly improves performance.

Note that this is an evil hack, which will break platforms where the ecc data is
non-continuous.
---
 drivers/mtd/nand/nand_base.c |   16 +++++-----------
 1 files changed, 5 insertions(+), 11 deletions(-)

--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -1011,8 +1011,8 @@ static int nand_read_page_hwecc_oob_firs
 	/* Read the OOB area first */
 	/* Read the OOB area first */
 	if (mtd->writesize > 512) {
-		chip->cmdfunc(mtd, NAND_CMD_READ0, mtd->writesize, page);
-		chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
+		chip->cmdfunc(mtd, NAND_CMD_READ0, mtd->writesize + eccpos[0], page);
+		chip->read_buf(mtd, ecc_code, chip->ecc.total);
 		chip->cmdfunc(mtd, NAND_CMD_RNDOUT, 0, -1);
 	} else {
 		chip->cmdfunc(mtd, NAND_CMD_READOOB, 0, page);
@@ -1020,9 +1020,6 @@ static int nand_read_page_hwecc_oob_firs
 		chip->cmdfunc(mtd, NAND_CMD_READ0, 0, page);
 	}
 
-	for (i = 0; i < chip->ecc.total; i++)
-		ecc_code[i] = chip->oob_poi[eccpos[i]];
-
 	for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
 		int stat;
 
@@ -1077,8 +1074,8 @@ static int nand_read_subpage_hwecc_oob_f
 
 	/* Read the OOB area first */
 	if (mtd->writesize > 512) {
-		chip->cmdfunc(mtd, NAND_CMD_READ0, mtd->writesize, page);
-		chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
+		chip->cmdfunc(mtd, NAND_CMD_READ0, mtd->writesize + eccpos[0], page);
+		chip->read_buf(mtd, ecc_code, chip->ecc.total);
 		chip->cmdfunc(mtd, NAND_CMD_RNDOUT, data_col_addr, -1);
 	} else {
 		chip->cmdfunc(mtd, NAND_CMD_READOOB, 0, page);
@@ -1086,9 +1083,6 @@ static int nand_read_subpage_hwecc_oob_f
 		chip->cmdfunc(mtd, NAND_CMD_READ0, data_col_addr, page);
 	}
 
-	for (i = 0; i < chip->ecc.total; i++)
-		ecc_code[i] = chip->oob_poi[eccpos[i]];
-
 	p = bufpoi + data_col_addr;
 
 	for (i = eccbytes * start_step; num_steps; num_steps--, i += eccbytes, p += eccsize) {