[PATCH 2/4] mtd: rawnand: Fix core interference with sequential reads

[Miquel Raynal]

On Fri, 2023-12-15 at 12:32:06 UTC, Miquel Raynal wrote:
> A couple of reports pointed at some strange failures happening a bit
> randomly since the introduction of sequential page reads support. After
> investigation it turned out the most likely reason for these issues was
> the fact that sometimes a (longer) read might happen, starting at the
> same page that was read previously. This is optimized by the raw NAND
> core, by not sending the READ_PAGE command to the NAND device and just
> reading out the data in a local cache. When this page is also flagged as
> being the starting point for a sequential read, it means the page right
> next will be accessed without the right instructions. The NAND chip will
> be confused and will not output correct data. In order to avoid such
> situation from happening anymore, we can however handle this case with a
> bit of additional logic, to postpone the initialization of the read
> sequence by one page.
> 
> Reported-by: Alexander Shiyan <eagle.alexander923 at gmail.com>
> Closes: https://lore.kernel.org/linux-mtd/CAP1tNvS=NVAm-vfvYWbc3k9Cx9YxMc2uZZkmXk8h1NhGX877Zg@mail.gmail.com/
> Reported-by: Måns Rullgård <mans at mansr.com>
> Closes: https://lore.kernel.org/linux-mtd/yw1xfs6j4k6q.fsf@mansr.com/
> Reported-by: Martin Hundebøll <martin at geanix.com>
> Closes: https://lore.kernel.org/linux-mtd/9d0c42fcde79bfedfe5b05d6a4e9fdef71d3dd52.camel@geanix.com/
> Fixes: 003fe4b9545b ("mtd: rawnand: Support for sequential cache reads")
> Cc: stable at vger.kernel.org
> Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/next.

Miquel