Re: i.MX25 NFC with 8 bit ecc strength

[Baruch Siach <baruch@tkos.co.il>]

Hi Uwe,

On Mon, Apr 20, 2015 at 09:37:02AM +0200, Uwe Kleine-König wrote:
> On Mon, Apr 20, 2015 at 07:56:14AM +0300, Baruch Siach wrote:
> > I'm trying to get nand_ecclayout right on i.MX25 with the Micron 
> > MT29F8G08ABABA (page size: 4096, oob size: 224). The large OOB size allows 
> Just for me to understand your plan: To support the big ecc variant you
> need another set of struct nand_ecclayout. The expectation for your
> flash would be:
> 
> 	.eccpos = { 8, ... 25,
> 			34, ... 51,
> 			60, ... 77,
> 			86, ... 103,
> 			112, ... 129,
> 			138, ... 155,
> 			164, ... 181,
> 			190, ... 207 }
> 
> right?

According to the dump below (28 bytes interval) it should be off by one:

	eccpos = { 7, ... 24,
		35, ... 52,
		63, ... 80,
		91, ... 108,
		119, ... 136,
		147, ... 164,
		175, ... 192,
		203, ... 220 };

> > using hardware ecc strength of 8bit per ecc step (512 bytes). The mxc_nand 
> > driver code (get_eccsize()) and the reference manual seems to indicate 
> > that enabling 8 bit ecc mode requires 26 oob bytes per ecc step. However, 
> > this seems to contradict the actual hardware test as the shown in the dump
> > below of a zero filled page + oob:
> > 
> > # hexdump -C dump4
> > 00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> > *
> > 00001000  ff ff ff ff ff ff ff 91  c4 45 be 32 45 6f 5d b1  |.........E.2Eo].|
> > 00001010  b1 b9 13 61 59 7d 42 58  eb ff ff ff ff ff ff ff  |...aY}BX........|
> > 00001020  ff ff ff 91 c4 45 be 32  45 6f 5d b1 b1 b9 13 61  |.....E.2Eo]....a|
> > 00001030  59 7d 42 58 eb ff ff ff  ff ff ff ff ff ff ff 91  |Y}BX............|
> > 00001040  c4 45 be 32 45 6f 5d b1  b1 b9 13 61 59 7d 42 58  |.E.2Eo]....aY}BX|
> > 00001050  eb ff ff ff ff ff ff ff  ff ff ff 91 c4 45 be 32  |.............E.2|
> > 00001060  45 6f 5d b1 b1 b9 13 61  59 7d 42 58 eb ff ff ff  |Eo]....aY}BX....|
> > 00001070  ff ff ff ff ff ff ff 91  c4 45 be 32 45 6f 5d b1  |.........E.2Eo].|
> > 00001080  b1 b9 13 61 59 7d 42 58  eb ff ff ff ff ff ff ff  |...aY}BX........|
> > 00001090  ff ff ff 91 c4 45 be 32  45 6f 5d b1 b1 b9 13 61  |.....E.2Eo]....a|
> > 000010a0  59 7d 42 58 eb ff ff ff  ff ff ff ff ff ff ff 91  |Y}BX............|
> > 000010b0  c4 45 be 32 45 6f 5d b1  b1 b9 13 61 59 7d 42 58  |.E.2Eo]....aY}BX|
> > 000010c0  eb ff ff ff ff ff ff ff  ff ff ff 91 c4 45 be 32  |.............E.2|
> > 000010d0  45 6f 5d b1 b1 b9 13 61  59 7d 42 58 eb ff ff ff  |Eo]....aY}BX....|
> > 
> > As you can easily see, ecc steps start at 28 bytes interval, with 18
> > bytes for ecc (matches documentation), and 10 bytes free.
> How did you extract this page+oob from the nand flash? From Linux I
> assume?

Got it form nanddump using:

	nanddump -s 5238784 -f dump4 -o /dev/mtd2


> Can you try from barebox something like:
> 
> 	mw -w 0xbb001e08 0x0000 # READ0
> 	mw -w 0xbb001e1c 0x01 # CMD cycle
> 	mw -w 0xbb001e06 0x00 # Address = 0
> 	mw -w 0xbb001e1c 0x02 # Address cycle
> 	mw -w 0xbb001e1c 0x02 # Address cycle
> 	mw -w 0xbb001e1c 0x02 # Address cycle (do we need three? [1])
> 	mw -w 0xbb001e04 0x00
> 	mw -w 0xbb001e1c 0x08 # NAND OUTPUT
> 	md -w 0xbb000000+0x10f0
> 
> with ecc being disabled (i.e. CONFIG1, bit 3 = 0). Does this show the 28
> bytes offset, too?

I (hopefuly) disabled ECC with:

	mw -w 0xbb001e1a 0x0010

Then, for the same page (using three address cycles, 0xff, 0x04, 0x00), I got 
all zeros up to 0xbb001000 (inclusive), and then:

bb001010: 0000 0000 0000 0000 0000 ffff 28a7 428a            .............(.B
bb001020: 89fa 2cd4 4640 560a 2634 ac7e e5d8 20ea            ...,@F.V4&~.... 
bb001030: caaa c809 0195 8411 6972 6bfc 84d6 10af            ........ri.k....
bb001040: 0000 0000 0000 0000 0000 0000 0000 0000            ................
bb001050: 0000 0000 0000 0000 0000 ffff f1da 19c3            ................
bb001060: 21b2 0832 09c6 3c55 638c 3bb8 fd54 2983            .!2...U<.c.;T..)
bb001070: 8325 6d98 0814 0d64 ee73 675e 1943 5cf2            %..m..d.s.^gC..\
bb001080: 0000 0000 0000 0000 0000 0000 0000 0000            ................
bb001090: 0000 0000 0000 0000 0000 ffff c1bc 31fe            ...............1
bb0010a0: 16ee ab6b 34a5 acad 0771 048c ac58 3f19            ..k..4..q...X..?
bb0010b0: b699 a88f eb5a 00ae 7e3c 9c6d 2ba8 d72e            ....Z...<~m..+..
bb0010c0: 0000 0000 0000 0000 0000 0000 0000 0000            ................
bb0010d0: 0000 0000 0000 0000 0000 ffff ae14 06c7            ................
bb0010e0: 89b9 eb67 00d0 3648 daeb 15f5 77ca 8c09            ..g...H6.....w..

I'm not sure what to do with that.

Thanks,
baruch

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