mtd: nand: enable software BCH ECC in nand simulator

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: NIvan Djelic <ivan.djelic@parrot.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>

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 +168,8 @@ 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 +2314,43 @@ static int __init ns_init_module(void)
 	if ((retval = parse_gravepages()) != 0)
 		goto error;
 
-	if ((retval = nand_scan(nsmtd, 1)) != 0) {
+	retval = nand_scan_ident(nsmtd, 1, NULL);
+	if (retval) {
+		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);
+	}
+
+	retval = nand_scan_tail(nsmtd);
+	if (retval) {
 		NS_ERR("can't register NAND Simulator\n");
 		if (retval > 0)
 			retval = -ENXIO;