RE: [PATCH] mtd: Expand the ecc placement locations to 1260

[Jeff Lauruhn (jlauruhn)]

This device has a Page size x8: 17,600 bytes (16,384 + 1216 bytes) and minimum required ECC 24-bit ECC per 1100 bytes of data.  Spare area needed for ECC would be ECC * M, where M is (codeword <= 2^m-1).  In this case M=14, because (1100*8)<=2^14-1, therefore minimum spare area needed is 14*24 = 336b or 42B per codeword.  So for this device a minimum of 672bytes of the 1216 need to be used for ECC, the rest can be used for other purposes.



Jeff Lauruhn
NAND Application Engineer


-----Original Message-----
From: linux-mtd [mailto:linux-mtd-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Punnaiah Choudary Kalluri
Sent: Thursday, March 19, 2015 1:50 AM
To: dwmw2@xxxxxxxxxxxxx; computersforpeace@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx; shaktib@xxxxxxxxxx; michals@xxxxxxxxxx; linux-mtd@xxxxxxxxxxxxxxxxxxx; kalluripunnaiahchoudary@xxxxxxxxx; Punnaiah Choudary Kalluri
Subject: [PATCH] mtd: Expand the ecc placement locations to 1260

Device like MT29F32G08ABCDBJ4 have a writesize/oobsize of 16K/1260 Bytes.
So, increasing the maximum ecc placement locations to 1260

Signed-off-by: Punnaiah Choudary Kalluri <punnaia@xxxxxxxxxx>
---
 include/linux/mtd/mtd.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h index f17fa75..e73d85b 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -95,7 +95,7 @@ struct mtd_oob_ops {
 };
 
 #define MTD_MAX_OOBFREE_ENTRIES_LARGE	32
-#define MTD_MAX_ECCPOS_ENTRIES_LARGE	640
+#define MTD_MAX_ECCPOS_ENTRIES_LARGE	1260
 /*
  * Internal ECC layout control structure. For historical reasons, there is a
  * similar, smaller struct nand_ecclayout_user (in mtd-abi.h) that is retained
--
1.7.4


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