[PATCH/RFC v3 3/3] mtd: nand: enable software BCH ECC in nand simulator

From: Ivan Djelic
Date: Wed Mar 09 2011 - 12:51:30 EST


This patch adds option 'bch' to nandsim, which can be used to enable
software BCH ECC (introduced in previous patches) and select BCH error
correction capability.

Signed-off-by: Ivan Djelic <ivan.djelic@xxxxxxxxxx>
---
v3 changelog:
No change.
v2 changelog
- do not handle small page devices

drivers/mtd/nand/nandsim.c | 40 +++++++++++++++++++++++++++++++++++++++-
1 files changed, 39 insertions(+), 1 deletions(-)

diff --git a/drivers/mtd/nand/nandsim.c b/drivers/mtd/nand/nandsim.c
index a5aa99f..e4ed5d7 100644
--- a/drivers/mtd/nand/nandsim.c
+++ b/drivers/mtd/nand/nandsim.c
@@ -34,6 +34,7 @@
#include <linux/string.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/nand.h>
+#include <linux/mtd/nand_bch.h>
#include <linux/mtd/partitions.h>
#include <linux/delay.h>
#include <linux/list.h>
@@ -108,6 +109,7 @@ static unsigned int rptwear = 0;
static unsigned int overridesize = 0;
static char *cache_file = NULL;
static unsigned int bbt;
+static unsigned int bch;

module_param(first_id_byte, uint, 0400);
module_param(second_id_byte, uint, 0400);
@@ -132,6 +134,7 @@ module_param(rptwear, uint, 0400);
module_param(overridesize, uint, 0400);
module_param(cache_file, charp, 0400);
module_param(bbt, uint, 0400);
+module_param(bch, uint, 0400);

MODULE_PARM_DESC(first_id_byte, "The first byte returned by NAND Flash 'read ID' command (manufacturer ID)");
MODULE_PARM_DESC(second_id_byte, "The second byte returned by NAND Flash 'read ID' command (chip ID)");
@@ -165,6 +168,7 @@ MODULE_PARM_DESC(overridesize, "Specifies the NAND Flash size overriding the I
" e.g. 5 means a size of 32 erase blocks");
MODULE_PARM_DESC(cache_file, "File to use to cache nand pages instead of memory");
MODULE_PARM_DESC(bbt, "0 OOB, 1 BBT with marker in OOB, 2 BBT with marker in data area");
+MODULE_PARM_DESC(bch, "Enable BCH ecc and set how many bits should be correctable in 512-byte blocks");

/* The largest possible page size */
#define NS_LARGEST_PAGE_SIZE 4096
@@ -2309,7 +2313,41 @@ static int __init ns_init_module(void)
if ((retval = parse_gravepages()) != 0)
goto error;

- if ((retval = nand_scan(nsmtd, 1)) != 0) {
+ if ((retval = nand_scan_ident(nsmtd, 1, NULL)) != 0) {
+ NS_ERR("cannot scan NAND Simulator device\n");
+ if (retval > 0)
+ retval = -ENXIO;
+ goto error;
+ }
+
+ if (bch) {
+ unsigned int eccsteps, eccbytes;
+ if (!mtd_nand_has_bch()) {
+ NS_ERR("BCH ECC support is disabled\n");
+ retval = -EINVAL;
+ goto error;
+ }
+ /* use 512-byte ecc blocks */
+ eccsteps = nsmtd->writesize/512;
+ eccbytes = (bch*13+7)/8;
+ /* do not bother supporting small page devices */
+ if ((nsmtd->oobsize < 64) || !eccsteps) {
+ NS_ERR("bch not available on small page devices\n");
+ retval = -EINVAL;
+ goto error;
+ }
+ if ((eccbytes*eccsteps+2) > nsmtd->oobsize) {
+ NS_ERR("invalid bch value %u\n", bch);
+ retval = -EINVAL;
+ goto error;
+ }
+ chip->ecc.mode = NAND_ECC_SOFT_BCH;
+ chip->ecc.size = 512;
+ chip->ecc.bytes = eccbytes;
+ NS_INFO("using %u-bit/%u bytes BCH ECC\n", bch, chip->ecc.size);
+ }
+
+ if ((retval = nand_scan_tail(nsmtd)) != 0) {
NS_ERR("can't register NAND Simulator\n");
if (retval > 0)
retval = -ENXIO;
--
1.7.2.3

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