From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A4C4DC7619A for ; Wed, 12 Apr 2023 14:32:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231292AbjDLOcX (ORCPT ); Wed, 12 Apr 2023 10:32:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59304 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229535AbjDLOcV (ORCPT ); Wed, 12 Apr 2023 10:32:21 -0400 Received: from relay3-d.mail.gandi.net (relay3-d.mail.gandi.net [IPv6:2001:4b98:dc4:8::223]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A1C0C10C0 for ; Wed, 12 Apr 2023 07:32:19 -0700 (PDT) Received: (Authenticated sender: miquel.raynal@bootlin.com) by mail.gandi.net (Postfix) with ESMTPSA id 90C1560010; Wed, 12 Apr 2023 14:32:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1681309938; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=uCd7H5EeqX9ceDa1o2Gu1VTH9DFW1VCWxDjFDqiS1qQ=; b=LKssq84Kl7yR39PBhA4l0CwJ9oc9/BCtrGaYHkESai2vuN384nsxSGkEHyADJqsH4TeLAx Sg01bTRmMbhiF0xOq3TF2CGT1fvDHT726d3d0nvJqLPHqgg6wrOxbMuE5Y7g1kC3ksnJ5d xU52cXuq5ryHiOxSMZ0QrXgrccjV05YlNsARc3+owYGJFDRQK3zBPIJEwR5AdbqaQU4UWu mJdI1mZKBCwRp9IT8jcTWdYfvvQJ7Onfil2a/Y1AXQ5mSmoAblFW5ewLra82q53mTzjlhI geYWaL+9GrYyRpl7hE7PbNLzfJf2JX/oXbR7xB2CqvHQhDUxH4KB1ywJQ0pihw== Date: Wed, 12 Apr 2023 16:32:14 +0200 From: Miquel Raynal To: Liang Yang Cc: Arseniy Krasnov , Richard Weinberger , Vignesh Raghavendra , Neil Armstrong , Kevin Hilman , Jerome Brunet , Martin Blumenstingl , Jianxin Pan , Yixun Lan , oxffffaa@gmail.com, kernel@sberdevices.ru, linux-mtd@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 4/5] mtd: rawnand: meson: clear OOB buffer before read Message-ID: <20230412163214.0c764bb3@xps-13> In-Reply-To: <7c996832-258f-001c-56bd-87bbdf23eeaa@amlogic.com> References: <20230412061700.1492474-1-AVKrasnov@sberdevices.ru> <20230412061700.1492474-5-AVKrasnov@sberdevices.ru> <20230412094400.3c82f631@xps-13> <20230412113654.183350d0@xps-13> <4eace0a0-f6af-7d99-a52f-7913a2139330@sberdevices.ru> <20230412141824.755b2bca@xps-13> <20230412145715.58c2be4a@xps-13> <7c996832-258f-001c-56bd-87bbdf23eeaa@amlogic.com> Organization: Bootlin X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, liang.yang@amlogic.com wrote on Wed, 12 Apr 2023 22:04:28 +0800: > Hi Miquel and Arseniy, >=20 > On 2023/4/12 20:57, Miquel Raynal wrote: > > [ EXTERNAL EMAIL ] > >=20 > > Hi Arseniy, > >=20 > > avkrasnov@sberdevices.ru wrote on Wed, 12 Apr 2023 15:22:26 +0300: > > =20 > >> On 12.04.2023 15:18, Miquel Raynal wrote: =20 > >>> Hi Arseniy, > >>> > >>> avkrasnov@sberdevices.ru wrote on Wed, 12 Apr 2023 13:14:52 +0300: =20 > >>> >>>> On 12.04.2023 12:36, Miquel Raynal wrote: =20 > >>>>> Hi Arseniy, > >>>>> > >>>>> avkrasnov@sberdevices.ru wrote on Wed, 12 Apr 2023 12:20:55 +0300: = =20 > >>>>> >>>>>> On 12.04.2023 10:44, Miquel Raynal wrote: =20 > >>>>>>> Hi Arseniy, > >>>>>>> > >>>>>>> AVKrasnov@sberdevices.ru wrote on Wed, 12 Apr 2023 09:16:58 +0300= : =20 > >>>>>>> >>>>>>>> This NAND reads only few user's bytes in ECC mode= (not full OOB), so =20 > >>>>>>> > >>>>>>> "This NAND reads" does not look right, do you mean "Subpage reads= do > >>>>>>> not retrieve all the OOB bytes,"? =20 > >>>>>>> >>>>>>>> fill OOB buffer with zeroes to not return garbage= from previous reads =20 > >>>>>>>> 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 > >>>>>>>> --- > >>>>>>>> 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/nan= d/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 n= and_chip *nand, > >>>>>>>> static int meson_nfc_read_page_raw(struct nand_chip *nand, u8 = *buf, > >>>>>>>> int oob_required, int page) > >>>>>>>> { > >>>>>>>> + struct mtd_info *mtd =3D nand_to_mtd(nand); > >>>>>>>> u8 *oob_buf =3D nand->oob_poi; > >>>>>>>> int ret; =20 > >>>>>>>> >>>>>>>> + memset(oob_buf, 0, mtd->oobsize); =20 > >>>>>>> > >>>>>>> I'm surprised raw reads do not read the entire OOB? =20 > >>>>>> > >>>>>> Yes! Seems in case of raw access (what i see in this driver) numbe= r 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 ha= s 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 re= ported as 64 bytes. =20 > >>>>> > >>>>> In all modes, when you read OOB, you should get the full OOB. The f= act > >>>>> 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. =20 > >>>> > >>>> 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)? =20 > >>> > >>> 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). =20 > >> > >> So "same amount of data", in ECC mode current implementation returns o= nly user OOB bytes (e.g. > >> OOB data excluding ECC codes), in raw it returns user bytes + ECC code= s. IIUC correct > >> behaviour is to always return user bytes + ECC codes as OOB data even = in ECC mode ? =20 > >=20 > > If the page are 2k+64B you should read 2k+64B when OOB are requested. > >=20 > > 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? =20 >=20 > 1) raw read can read out the whole page data 2k+64B, decided by the len i= n the controller raw read command: > cmd =3D (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 =3D (nand->ecc.bytes + 2) * nand->ecc.steps; > memcpy(oob_buf + oob_len, meson_chip->data_buf + oob_len, mtd->oobsize = - oob_len); >=20 > } > 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. >=20 > >=20 > > 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 > >=20 > > 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. > >=20 > > Thanks, > > Miqu=C3=A8l > > =20 >=20 Thanks, Miqu=C3=A8l