linux-kernel - Re: [PATCH 4.4 03/34] mtd: nand: gpmi: Fix failure when a erased page has a bitflip at BBM

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Date:   Tue, 06 Mar 2018 21:22:30 +0000
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org, Sascha Hauer <s.hauer@...gutronix.de>,
        Richard Weinberger <richard@....at>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: Re: [PATCH 4.4 03/34] mtd: nand: gpmi: Fix failure when a erased
 page has a bitflip at BBM

On Fri, 2018-03-02 at 09:50 +0100, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Sascha Hauer <s.hauer@...gutronix.de>
> 
> 
> [ Upstream commit fdf2e821052958a114618a95ab18a300d0b080cb ]
> 
> When erased subpages are read then the BCH decoder returns STATUS_ERASED
> if they are all empty, or STATUS_UNCORRECTABLE if there are bitflips.
> When there are bitflips, we have to set these bits again to show the
> upper layers a completely erased page. When a bitflip happens in the
> exact byte where the bad block marker is, then this byte is swapped
> with another byte in block_mark_swapping(). The correction code then
> detects a bitflip in another subpage and no longer corrects the bitflip
> where it really happens.
[...]

This seesm to be a bug fix for commit bd2e778c9ee3 "gpmi-nand: Handle
ECC Errors in erased pages".  That's not in 4.4 so the bug fix is not
needed, though it doesn't appear to do any harm.

Ben.

-- 
Ben Hutchings
Software Developer, Codethink Ltd.