Re: [RFC PATCH v5 0/6] refactoring, fixes and updates for Meson NAND

Miquel Raynal
2023-06-01T07:51:01Z

Hi Arseniy,

AVKrasnov@sberdevices.ru wrote on Thu, 1 Jun 2023 09:18:43 +0300:

> Hello,
>
> this patchset does several things:

All the fixes should contain:

Fixes: <hash> ("log")
Cc: stable@vger.kernel.org

>
> 1) Fixes value of ready/busy command. This new value was suggested by
> Liang Yang <liang.yang@amlogic.com>.
>
> 2) Adds waiting for command completion by calling 'nand_soft_waitrdy()'
> instead of using ready/busy pin and command from 1). This is really
> needed because I don't have device with such pin implemented.
>
> 3) It moves OOB free bytes to non-protected by ECC area. Here are some
> details:
>
> Current OOB free bytes are 4 bytes (2 x 2 user bytes) under ECC engine.
> Here is how it looks like in the current implementation:
>
> [ 2B user bytes ][ 14B ECC codes ]
> [ 2B user bytes ][ 14B ECC codes ]
> [ 16B unused area, not protected by ECC ]
> [ 16B unused area, not protected by ECC ]
>
> All 4 user bytes are protected by ECC. This patch changes OOB free
> bytes in this way:
>
> [ 2B unused area ][ 14B ECC codes ]
> [ 2B unused area ][ 14B ECC codes ]
> [ 16B user bytes, not protected by ECC ]
> [ 16B user bytes, not protected by ECC ]
>
> Now OOB user bytes are 32 bytes instead of 4 bytes and not protected
> by ECC.
>
> Motivation of this layout comes from problem with JFFS2. It uses OOB
> free bytes for cleanmarkers. Each cleanmarker is 4 bytes and written
> by JFFS2 driver (small remark - cleanmarkers are always written in
> case of NAND storage for JFFS2).
> We have two ways to write this data to OOB (e.g. user bytes):
>
> 1) ECC mode. In this case it will be ECC covered user bytes, e.g.
> writing this bytes will update ECC codes. Problem fires, when
> JFFS2 tries to write this page later - this write makes controller
> to update ECC codes again, but it is impossible to do it correctly,
> because we can't update bits from 0 to 1 (only from 1 to 0).
>
> 2) Raw mode. In this case ECC codes won't be updated. But later, it
> will be impossible to read this page in ECC mode, because we have
> some user bytes, but ECC codes are missed.
>
> So let's move OOB free bytes out of ECC area. In this case we can
> read/write OOB separately in raw mode and at the same time work with
> data in ECC mode. JFFS2 is happy now. User bytes are untouched - all
> of them are ignored during non-OOB access.
>
> I've tested this with mount/unmount/read/write cases for JFFS2 and
> nanddump/nandwrite utlities on AXG family (A113X SoC).
>
> Here is link to discussion:
> https://lore.kernel.org/linux-mtd/a9f8307a-77d7-a69f-ce11-2629909172d2@sberdevices.ru/T/#m3087bd06386a7f430cd5e343e22b25d724d3e2d7
>
> 4) Replaces calculation of OOB related thing with macros. This is just
> cosmetic change.
>
> 5) Checks buffer length on accesses to NAND controller.
>
> 6) Removes useless bitwise OR with zeroes.
>
> Link to v1:
> https://lore.kernel.org/linux-mtd/20230412061700.1492474-1-AVKrasnov@sberdevices.ru/
> Link to v2:
> https://lore.kernel.org/linux-mtd/20230426073632.3905682-1-AVKrasnov@sberdevices.ru/
> Link to v3:
> https://lore.kernel.org/linux-mtd/20230510110835.26115-1-AVKrasnov@sberdevices.ru/
> Link to v4:
> https://lore.kernel.org/linux-mtd/20230515094440.3552094-1-AVKrasnov@sberdevices.ru/
>
> Changelog:
>
> v1 -> v2:
> * Add patch which renames dts value for chip select.
> * Add patch which moves OOB to non-protected ECC area.
> v2 -> v3:
> * Change patch which fixes read/write access according discussion link
> in 1) above.
> v3 -> v4:
> * Remove patch which renames dts value for chip select.
> Here is link to discussion:
> https://lore.kernel.org/linux-mtd/20230510110835.26115-7-AVKrasnov@sberdevices.ru/
> * Pass 1 to 'meson_nfc_queue_rb()' in case of NAND_OP_WAITRDY_INSTR.
> This fixes ONFI page processing during NAND driver initialization.
> v4 -> v5:
> * Move update of 'NFC_CMD_RB_INT' to the separate patch.
> * Replace code which uses extra status and READ0 commands for waiting
> command with 'nand_soft_waitrdy()'. In fact this patch adds second
> mode for command waiting by using 'nand_soft_waitrdy()'.
> * For OOB layout patch see changelog in a patch file.
> * For check length patch see changelog in a patch file.
>
> Arseniy Krasnov (6):
> mtd: rawnand: meson: fix ready/busy command
> mtd: rawnand: meson: wait for command in polling mode
> mtd: rawnand: meson: only expose unprotected user OOB bytes
> mtd: rawnand: meson: use macro for OOB area
> mtd: rawnand: meson: check buffer length
> mtd: rawnand: meson: remove unneeded bitwise OR with zeroes
>
> drivers/mtd/nand/raw/meson_nand.c | 234 +++++++++++++++++++++++-------
> 1 file changed, 182 insertions(+), 52 deletions(-)
>

Thanks,
Miquèl