Messages in this thread | | | Date | Wed, 12 Apr 2023 14:18:24 +0200 | From | Miquel Raynal <> | Subject | Re: [PATCH v1 4/5] mtd: rawnand: meson: clear OOB buffer before read |
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Hi Arseniy,
avkrasnov@sberdevices.ru wrote on Wed, 12 Apr 2023 13:14:52 +0300:
> On 12.04.2023 12:36, Miquel Raynal wrote: > > Hi Arseniy, > > > > avkrasnov@sberdevices.ru wrote on Wed, 12 Apr 2023 12:20:55 +0300: > > > >> On 12.04.2023 10:44, Miquel Raynal wrote: > >>> Hi Arseniy, > >>> > >>> AVKrasnov@sberdevices.ru wrote on Wed, 12 Apr 2023 09:16:58 +0300: > >>> > >>>> This NAND reads only few user's bytes in ECC mode (not full OOB), so > >>> > >>> "This NAND reads" does not look right, do you mean "Subpage reads do > >>> not retrieve all the OOB bytes,"? > >>> > >>>> fill OOB buffer with zeroes to not return garbage from previous reads > >>>> to user. > >>>> Otherwise 'nanddump' utility prints something like this for just erased > >>>> page: > >>>> > >>>> ... > >>>> 0x000007f0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > >>>> OOB Data: ff ff ff ff 00 00 ff ff 80 cf 22 99 cb ad d3 be > >>>> OOB Data: 63 27 ae 06 16 0a 2f eb bb dd 46 74 41 8e 88 6e > >>>> OOB Data: 38 a1 2d e6 77 d4 05 06 f2 a5 7e 25 eb 34 7c ff > >>>> OOB Data: 38 ea de 14 10 de 9b 40 33 16 6a cc 9d aa 2f 5e > >>>> > >>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru> > >>>> --- > >>>> drivers/mtd/nand/raw/meson_nand.c | 5 +++++ > >>>> 1 file changed, 5 insertions(+) > >>>> > >>>> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c > >>>> index f84a10238e4d..f2f2472cb511 100644 > >>>> --- a/drivers/mtd/nand/raw/meson_nand.c > >>>> +++ b/drivers/mtd/nand/raw/meson_nand.c > >>>> @@ -858,9 +858,12 @@ static int meson_nfc_read_page_sub(struct nand_chip *nand, > >>>> static int meson_nfc_read_page_raw(struct nand_chip *nand, u8 *buf, > >>>> int oob_required, int page) > >>>> { > >>>> + struct mtd_info *mtd = nand_to_mtd(nand); > >>>> u8 *oob_buf = nand->oob_poi; > >>>> int ret; > >>>> > >>>> + memset(oob_buf, 0, mtd->oobsize); > >>> > >>> I'm surprised raw reads do not read the entire OOB? > >> > >> Yes! Seems in case of raw access (what i see in this driver) number of OOB bytes read > >> still depends on ECC parameters: for each portion of data covered with ECC code we can > >> read it's ECC code and "user bytes" from OOB - it is what i see by dumping DMA buffer by > >> printk(). For example I'm working with 2K NAND pages, each page has 2 x 1K ECC blocks. > >> For each ECC block I have 16 OOB bytes which I can access by read/write. Each 16 bytes > >> contains 2 bytes of user's data and 14 bytes ECC codes. So when I read page in raw mode > >> controller returns 32 bytes (2 x (2 + 14)) of OOB. While OOB is reported as 64 bytes. > > > > In all modes, when you read OOB, you should get the full OOB. The fact > > that ECC correction is enabled or disabled does not matter. If the NAND > > features OOB sections of 64 bytes, you should get the 64 bytes. > > > > What happens sometimes, is that some of the bytes are not protected > > against bitflips, but the policy is to return the full buffer. > > Ok, so to clarify case for this NAND controller: > 1) In both ECC and raw modes i need to return the same raw OOB data (e.g. user bytes > + ECC codes)?
Well, you need to cover the same amount of data, yes. But in the ECC case the data won't be raw (at least not all of it).
> 2) If I have access to only 32 bytes of OOB (in case above), I must report that size > of OOB is only 32 bytes during initialization?
I believe it's just an implementation error in the controller driver. This controller can be used on NAND chips with other geometries, please don't play with it.
Thanks, Miquèl
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