Hi Daniel, Daniel Palmer <dan...@0x0f.com> wrote on Mon, 22 Mar 2021 21:44:40 +0900:
> Hi Miquel, > > Sorry for the resend. Gmail randomly switched to HTML email so the > original version seems to have bounced. > > On Mon, 15 Feb 2021 at 20:16, Miquel Raynal <miquel.ray...@bootlin.com> wrote: > > > "2. Spare area 800H to 83FH is all available for user. > > > ECC parity codes are programmed in > > > additional space and not user accessible." > > > > > > It would seem that the pages are actually bigger than 2K + 64 or there > > > is some other place they keep the ECC. > > > Or both datasheets are lying. Somewhere else in the datasheets it says > > > that writes to the ECC area will be ignored but that doesn't make a > > > lot of sense if the ECC area isn't user accessible in the first place. > > > > > > I didn't think about it at the time but I can take a dump of the OOB > > > area of my FS35ND01G-S1Y2 to confirm it's all 0xff except for any > > > factory marked bad blocks. > > > > I see. Can you please try the following: > > > > nandwrite -o /dev/mtdx /dev/zero > > nanddump -ol1 /dev/mtdx > > If the entire area is effectively free to be used, you should see 0's > > everywhere. Otherwise you should have ff's somewhere. > > Sorry I didn't follow up sooner on this. I needed to order another of > this flash chip to test with as I couldn't destroy the data on the one > I have. > > Anyhow: > > Erased the page with flash erase (I'm forcing it to erase bad blocks > here as I mess up the marker, I have a hack to allow erasing bad > blocks..) > Everything is 0xFF for that page. > > # flash_erase -N /dev/mtd1 0 1 > Erasing 128 Kibyte @ 0 -- 100 % complete > # nanddump --bb=dumpbad -n -l2048 -o -c -s 0x0 /dev/mtd1 > Block size 131072, page size 2048, OOB size 64 > Dumping data starting at 0x00000000 and ending at 0x00000800... > 0x00000000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > |................| > .... > 0x000007f0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > |................| > OOB Data: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > |................| > OOB Data: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > |................| > OOB Data: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > |................| > OOB Data: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > |................| > > Write zeros into the page and OOB. > Get all zeros back including the OOB. > > # nandwrite -o /dev/mtd1 /dev/zero > Writing data to block 0 at offset 0x0 > Bad block at 0, 1 block(s) will be skipped > Writing data to block 1 at offset 0x20000 > # nandwrite -N -o /dev/mtd1 /dev/zero > Writing data to block 0 at offset 0x0 > # nanddump --bb=dumpbad -n -l2048 -o -c -s 0x0 /dev/mtd1 > Block size 131072, page size 2048, OOB size 64 > Dumping data starting at 0x00000000 and ending at 0x00000800... > 0x00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > |................| > ... > 0x000007f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > |................| > OOB Data: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > |................| > OOB Data: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > |................| > OOB Data: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > |................| > OOB Data: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > |................| > > Erase the page again and writing random junk into it. > Seeing random junk everywhere including the OOB. > > # flash_erase -N /dev/mtd1 0 1 > Erasing 128 Kibyte @ 0 -- 100 % complete > # nandwrite -N -o /dev/mtd1 /dev/urandom > Writing data to [ 230.506260] random: nandwrite: uninitialized > urandom read (2048 bytes read) > block 0 at offse[ 230.514705] random: nandwrite: uninitialized > urandom read (64 bytes read) > t 0x0 > # nanddump --bb=dumpbad -n -l2048 -o -c -s 0x0 /dev/mtd1 > Block size 131072, page size 2048, OOB size 64 > Dumping data starting at 0x00000000 and ending at 0x00000800... > 0x00000000: 5e 24 bd 5f d9 c6 ce c5 b1 85 52 4d 27 94 c9 98 > |^$._......RM'...| > ... > 0x000007f0: fa 9f 7f 7d ce 99 33 88 d6 9f 99 7d 84 e7 0c 4d > |...}..3....}...M| > OOB Data: b1 81 07 6a 8d 47 8b ed 89 88 ac 62 e8 ae 48 54 > |...j.G.....b..HT| > OOB Data: 7d b2 ea 73 f3 29 ba 65 e6 45 cb 8b 1a c6 5b dc > |}..s.).e.E....[.| > OOB Data: b2 2e 77 56 e0 e1 04 59 86 31 7a e5 bd 43 f9 48 > |..wV...Y.1z..C.H| > OOB Data: 52 05 b2 f1 65 64 59 22 79 50 ec 89 55 6b 6e 23 > |R...edY"yP..Ukn#| > > I think this shows that the datasheet is right in that the complete 64 > bytes of "spare area" is usable. > I have no idea where it puts the ECC though. :) Argh, I don't like when hardware tries to be smart. Ok then let's declare no ECC bytes in the OOB layout, I guess it's the best thing to do... Thanks for checking btw! I don't recall the state of the patch which triggered this discussion, so I guess it's a good time to respin. Cheers, Miquèl
