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

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Message-ID: <0D23F1ECC880A74392D56535BCADD7354973F1C7@NTXBOIMBX03.micron.com>
Date:	Thu, 19 Mar 2015 23:21:35 +0000
From:	"Jeff Lauruhn (jlauruhn)" <jlauruhn@...ron.com>
To:	Punnaiah Choudary Kalluri <punnaiah.choudary.kalluri@...inx.com>,
	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	"computersforpeace@...il.com" <computersforpeace@...il.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"shaktib@...inx.com" <shaktib@...inx.com>,
	"michals@...inx.com" <michals@...inx.com>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"kalluripunnaiahchoudary@...il.com" 
	<kalluripunnaiahchoudary@...il.com>,
	Punnaiah Choudary Kalluri <punnaia@...inx.com>
Subject: RE: [PATCH] mtd: Expand the ecc placement locations to 1260

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@...ts.infradead.org] On Behalf Of Punnaiah Choudary Kalluri
Sent: Thursday, March 19, 2015 1:50 AM
To: dwmw2@...radead.org; computersforpeace@...il.com
Cc: linux-kernel@...r.kernel.org; shaktib@...inx.com; michals@...inx.com; linux-mtd@...ts.infradead.org; kalluripunnaiahchoudary@...il.com; 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@...inx.com>
---
 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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