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From:   Ahmad Fatoum <a.fatoum@pengutronix.de>
Subject: Re: [BUG] mtd: cfi_cmdset_0002: write regression since v4.17-rc1
To:     Tokunori Ikegami <ikegami.t@gmail.com>,
        Thorsten Leemhuis <regressions@leemhuis.info>,
        linux-mtd@lists.infradead.org, Joakim.Tjernlund@infinera.com,
        miquel.raynal@bootlin.com, vigneshr@ti.com, richard@nod.at,
        "regressions@lists.linux.dev" <regressions@lists.linux.dev>
Cc:     Chris Packham <chris.packham@alliedtelesis.co.nz>,
        Brian Norris <computersforpeace@gmail.com>,
        David Woodhouse <dwmw2@infradead.org>, marek.vasut@gmail.com,
        cyrille.pitchen@wedev4u.fr,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        linuxppc-dev@lists.ozlabs.org, Shaohui.Xie@nxp.com
References: <b687c259-6413-26c9-d4c9-b3afa69ea124@pengutronix.de>
 <dff2abcc-5813-2f2c-35ba-f03cd1f35ac3@leemhuis.info>
 <e11b76dc-5539-fb7e-da1c-a5005713d6b0@gmail.com>
Message-ID: <3dbbcee5-81fc-cdf5-9f8b-b6ccb95beddc@pengutronix.de>
Date:   Fri, 28 Jan 2022 13:55:55 +0100
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Hello Tokunori-san,

On 15.12.21 18:34, Tokunori Ikegami wrote:
> Hi Ahmad-san,

Thanks for your reply (and Thorsten for the reminder) and sorry for
the delay. I had a lot of backlog after my time off.

> Sorry for the regression issue by the change: dfeae1073583.
> To make sure could you please try with the word write instead of the buffered writes?

The issue is still there with #define FORCE_WORD_WRITE 1:

  jffs2: Write clean marker to block at 0x000a0000 failed: -5
  MTD do_write_oneword_once(): software timeout

> FYI: There are some changes to disable the buffered writes as below.
>   1. https://git.openwrt.org/?p=openwrt/openwrt.git;a=blob;f=target/linux/ar71xx/patches-4.9/411-mtd-cfi_cmdset_0002-force-word-write.patch;h=ddd69f17e1ac16e8fc3a694c56231fee1e2ef149;hb=fec8fe806963c96a6506c2aebc3572d3a11f285f
>   2. https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/mtd/chips/cfi_cmdset_0002.c?h=v5.16-rc5&id=7e4404113686868858a34210c28ae122e967aa64
> 
> Note:
>   Currently I am not able to investigate the issue on the product for the change before.
> 
>   By the way in the past I had investigated the similar issue on Buffalo WZR-HP-G300NH using the S29GL256N.
>   It was not able to find the root cause by the investigation since not required actually at that time.
>   Also actually the buffered writes were disabled on the OpenWrt firmware as the change [1] above.
>   But I am not sure the reason detail to disable the buffered writes on the OpenWrt firmware.
>   I thought the issue not caused by the change: dfeae1073583 since the issue happened without the change.
> 
>   So I am not sure why the above change [2] needed to disable the buffered writes on Buffalo WZR-HP-G300NH.
>   Probably seems needed to disable the buffered writes on the other firmware also but not OpenWrt firmware.
> 
>   Anyway there are difference with your regression issue as below.
>     1. Flash device: S29GL064N (Your regression issue), S29GL256N (WZR-HP-G300NH)
>     2. Regression issue: Yes (Your regression issue), No (WZR-HP-G300NH as I investigated before)

Doesn't seem to be a buffered write issue here though as the writes
did work fine before dfeae1073583. Any other ideas?

Cheers,
Ahmad

> 
> Regards,
> Ikegami
> 
> On 2021/12/14 16:23, Thorsten Leemhuis wrote:
>> [TLDR: adding this regression to regzbot; most of this mail is compiled
>> from a few templates paragraphs some of you might have seen already.]
>>
>> Hi, this is your Linux kernel regression tracker speaking.
>>
>> Top-posting for once, to make this easy accessible to everyone.
>>
>> Thanks for the report.
>>
>> Adding the regression mailing list to the list of recipients, as it
>> should be in the loop for all regressions, as explained here:
>> https://www.kernel.org/doc/html/latest/admin-guide/reporting-issues.html
>>
>> To be sure this issue doesn't fall through the cracks unnoticed, I'm
>> adding it to regzbot, my Linux kernel regression tracking bot:
>>
>> #regzbot ^introduced dfeae1073583
>> #regzbot title mtd: cfi_cmdset_0002: flash write accesses on the
>> hardware fail on a PowerPC MPC8313 to a 8-bit-parallel S29GL064N flash
>> #regzbot ignore-activity
>>
>> Reminder: when fixing the issue, please add a 'Link:' tag with the URL
>> to the report (the parent of this mail), then regzbot will automatically
>> mark the regression as resolved once the fix lands in the appropriate
>> tree. For more details about regzbot see footer.
>>
>> Sending this to everyone that got the initial report, to make all aware
>> of the tracking. I also hope that messages like this motivate people to
>> directly get at least the regression mailing list and ideally even
>> regzbot involved when dealing with regressions, as messages like this
>> wouldn't be needed then.
>>
>> Don't worry, I'll send further messages wrt to this regression just to
>> the lists (with a tag in the subject so people can filter them away), as
>> long as they are intended just for regzbot. With a bit of luck no such
>> messages will be needed anyway.
>>
>> Ciao, Thorsten (wearing his 'Linux kernel regression tracker' hat).
>>
>> P.S.: As a Linux kernel regression tracker I'm getting a lot of reports
>> on my table. I can only look briefly into most of them. Unfortunately
>> therefore I sometimes will get things wrong or miss something important.
>> I hope that's not the case here; if you think it is, don't hesitate to
>> tell me about it in a public reply. That's in everyone's interest, as
>> what I wrote above might be misleading to everyone reading this; any
>> suggestion I gave thus might sent someone reading this down the wrong
>> rabbit hole, which none of us wants.
>>
>> BTW, I have no personal interest in this issue, which is tracked using
>> regzbot, my Linux kernel regression tracking bot
>> (https://linux-regtracking.leemhuis.info/regzbot/). I'm only posting
>> this mail to get things rolling again and hence don't need to be CC on
>> all further activities wrt to this regression.
>>
>> On 13.12.21 14:24, Ahmad Fatoum wrote:
>>> Hi,
>>>
>>> I've been investigating a breakage on a PowerPC MPC8313: The SoC is connected
>>> via the "Enhanced Local Bus Controller" to a 8-bit-parallel S29GL064N flash,
>>> which is represented as a memory-mapped cfi-flash.
>>>
>>> The regression began in v4.17-rc1 with
>>>
>>>    dfeae1073583 ("mtd: cfi_cmdset_0002: Change write buffer to check correct value")
>>>
>>> and causes all flash write accesses on the hardware to fail. Example output
>>> after v5.1-rc2[1]:
>>>
>>>    root@host:~# mount -t jffs2 /dev/mtdblock0 /mnt
>>>    MTD do_write_buffer_wait(): software timeout, address:0x000c000b.
>>>    jffs2: Write clean marker to block at 0x000c0000 failed: -5
>>>
>>> This issue still persists with v5.16-rc. Reverting aforementioned patch fixes
>>> it, but I am still looking for a change that keeps both Tokunori's and my
>>> hardware happy.
>>>
>>> What Tokunori's patch did is that it strengthened the success condition
>>> for flash writes:
>>>
>>>   - Prior to the patch, DQ polling was done until bits
>>>     stopped toggling. This was taken as an indicator that the write succeeded
>>>     and was reported up the stack. i.e. success condition is chip_ready()
>>>
>>>   - After the patch, polling continues until the just written data is
>>>     actually read back, i.e. success condition is chip_good()
>>>
>>> This new condition never holds for me, when DQ stabilizes, it reads 0xFF,
>>> never the just written data. The data is still written and can be read back
>>> on subsequent reads, just not at that point of time in the poll loop.
>>>
>>> We haven't had write issues for the years predating that patch. As the
>>> regression has been mainline for a while, I am wondering what about my setup
>>> that makes it pop up here, but not elsewhere?
>>>
>>> I consulted the data sheet[2] and found Figure 27, which describes DQ polling
>>> during embedded algorithms. DQ switches from status output to "True" (I assume
>>> True == all bits set == 0xFF) until CS# is reasserted.
>>>
>>> I compared with another chip's datasheet, and it (Figure 8.4) doesn't describe
>>> such an intermittent "True" state. In any case, the driver polls a few hundred
>>> times, however, before giving up, so there should be enough CS# toggles.
>>>
>>>
>>> Locally, I'll revert this patch for now. I think accepting 0xFF as a success
>>> condition may be appropriate, but I don't yet have the rationale to back it up.
>>>
>>> I am investigating this some more, probably with a logic trace, but I wanted
>>> to report this in case someone has pointers and in case other people run into
>>> the same issue.
>>>
>>>
>>> Cheers,
>>> Ahmad
>>>
>>> [1] Prior to d9b8a67b3b95 ("mtd: cfi: fix deadloop in cfi_cmdset_0002.c do_write_buffer")
>>>      first included with v5.1-rc2, failing writes just hung indefinitely in kernel space.
>>>      That's fixed, but the writes still fail.
>>>
>>> [2]: 001-98525 Rev. *B, https://www.infineon.com/dgdl/Infineon-S29GL064N_S29GL032N_64_Mbit_32_Mbit_3_V_Page_Mode_MirrorBit_Flash-DataSheet-v03_00-EN.pdf?fileId=8ac78c8c7d0d8da4017d0ed556fd548b
>>>
>>> [3]: https://www.mouser.com/datasheet/2/268/SST39VF1601C-SST39VF1602C-16-Mbit-x16-Multi-Purpos-709008.pdf
>>>       Note that "true data" means valid data here, not all bits one.
>>>
> 


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