Messages in this thread | | | Date | Wed, 12 Apr 2023 16:32:14 +0200 | From | Miquel Raynal <> | Subject | Re: [PATCH v1 4/5] mtd: rawnand: meson: clear OOB buffer before read |
| |
Hello,
liang.yang@amlogic.com wrote on Wed, 12 Apr 2023 22:04:28 +0800:
> Hi Miquel and Arseniy, > > On 2023/4/12 20:57, Miquel Raynal wrote: > > [ EXTERNAL EMAIL ] > > > > Hi Arseniy, > > > > avkrasnov@sberdevices.ru wrote on Wed, 12 Apr 2023 15:22:26 +0300: > > > >> On 12.04.2023 15:18, Miquel Raynal wrote: > >>> 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). > >> > >> So "same amount of data", in ECC mode current implementation returns only user OOB bytes (e.g. > >> OOB data excluding ECC codes), in raw it returns user bytes + ECC codes. IIUC correct > >> behaviour is to always return user bytes + ECC codes as OOB data even in ECC mode ? > > > > If the page are 2k+64B you should read 2k+64B when OOB are requested. > > > > If the controller only returns 2k+32B, then perform a random read to > > just move the read pointer to mtd->size + mtd->oobsize - 32 and > > retrieve the missing 32 bytes? > > 1) raw read can read out the whole page data 2k+64B, decided by the len in the controller raw read command: > cmd = (len & GENMASK(5, 0)) | scrambler | DMA_DIR(dir); > after that, the missing oob bytes(not used) can be copied from meson_chip->data_buf. so the implementation of meson_nfc_read_page_raw() is like this if need. > { > ...... > meson_nfc_read_page_sub(nand, page, 1); > meson_nfc_get_data_oob(nand, buf, oob_buf); > oob_len = (nand->ecc.bytes + 2) * nand->ecc.steps; > memcpy(oob_buf + oob_len, meson_chip->data_buf + oob_len, mtd->oobsize - oob_len); > > } > 2) In ECC mode, the controller can't bring back the missing OOB bytes. it can read out the user bytes and ecc bytes per meson_ooblayout_ops define.
And then (if oob_required) you can bring the missing bytes with something along: nand_change_read_column_op(chip, mtd->writesize + oob_len, oob_buf + oob_len, mtd->oobsize - oob_len, false); Should not be a huge performance hit.
> > > > > This applies to the two modes, the only difference is: > > - with correction (commonly named "ECC mode"): the user bytes and ECC > > bytes should be fixed if there are any bitflips > > - without correction (commonly referred as "raw mode"): no correction > > applies, if there are bitflips, give them > > > > Please mind the raw mode can be slow, it's meant for debugging and > > testing, mainly. Page reads however should be fast, so if just moving > > the column pointer works, then do it, otherwise we'll consider > > returning FFs. > > > > Thanks, > > Miquèl > > >
Thanks, Miquèl
| |