Re: [PATCH] spi-nor: Verify written data in paranoid mode

From: Richard Weinberger <richard@nod.at>
To: "Csókás Bence" <csokas.bence@prolan.hu>
Cc: "Michael Walle" <mwalle@kernel.org>,
	linux-mtd <linux-mtd@lists.infradead.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	"Tamás Szentendrei" <szentendrei.tamas@prolan.hu>,
	"Tudor Ambarus" <tudor.ambarus@linaro.org>,
	pratyush <pratyush@kernel.org>,
	"Miquel Raynal" <miquel.raynal@bootlin.com>,
	"Vignesh Raghavendra" <vigneshr@ti.com>
Subject: Re: [PATCH] spi-nor: Verify written data in paranoid mode
Date: Wed, 16 Apr 2025 20:41:18 +0200 (CEST)	[thread overview]
Message-ID: <81225127.297167214.1744828878236.JavaMail.zimbra@nod.at> (raw)
In-Reply-To: <c56c52c0-a824-4ad7-9847-e0e973f811ed@prolan.hu>

----- Ursprüngliche Mail -----
> Von: "Csókás Bence" <csokas.bence@prolan.hu>
>> I'm not so sure whether it makes sense at all.
>> In it's current form, there is no recovery. So anything non-trivial
>> on top of the MTD will just see an -EIO and has to give up.
>> E.g. a filesystem will remount read-only.
> 
> In our case, we use UBIFS on top of UBI, which in this case chooses
> another eraseblock to hold the data instead, then re-tests (erase+write
> cycles) the one which gave -EIO. Since the bus error is only transient,
> it goes away by this time, and thus UBIFS will recover from this cleanly.

Are you sure about that?

I'd expect UBI to go into RO mode via a call path like:
ubi_eba_write_leb() -> ubi_io_write() -> mtd_write()
If mtd_write() returns an EIO, UBI will go into RO mode immediately.

(I'm assuming, your SPI-NOR has no bad block support, so ubi->bad_allowed
is false).

Thanks,
//richard

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