[PATCH v2] mtd: nand: support BENAND (Built-in ECC NAND)

[katsuki.uwatoko at toshiba.co.jp]

> > > Just inquisitive, can anyone please share any throughput comparison
> > between 'BENAND' & 'normal NAND' devices having same capacity and
> > working on same clock-freq ?

I think that the following would be helpful.

http://www.toshiba-components.com/memory/benand.html
http://www.toshiba-components.com/memory/data/BENAND%20QA_V1.0_121031.pdf
http://www.toshiba-components.com/memory/data/Whitepaper_BENAND_11_2012.pdf

> But assuming there is no file-system OOB metadata | cleanmarker to be stored (like in UBIFS)
> Do we still need to transfer OOB data from Host processor to NAND device ?

No, we don't.

> how do we ensure that layout of metadata does not overlap with ECC syndrome in BENAND ?
> Is the BENAND capable of re-adjusting its ECC layout ? 

The area which we can use is defined as nand_ecclayout in nand_benand.c.
And the area is covered by the built-in ECC.

+static struct nand_ecclayout benand_oob_128 = {
+	.oobfree = {
+		{.offset = 2, .length = 3},
+		{.offset = 18, .length = 3},
+		{.offset = 34, .length = 3},
+		{.offset = 50, .length = 3},
+		{.offset = 66, .length = 3},
+		{.offset = 82, .length = 3},
+		{.offset = 98, .length = 3},
+		{.offset = 114, .length = 3},
+	}
+};

In the case of 24nm products, which are NOT 128bytes OOB type, 
the whole area of OOB can be available and is covered by the built-in ECC. 
-- 
UWATOKO Katsuki