Date:   Mon, 14 Feb 2022 01:47:57 +0900
From:   Tokunori Ikegami <ikegami.t@...il.com>
To:     Ahmad Fatoum <a.fatoum@...gutronix.de>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        linux-mtd@...ts.infradead.org, Joakim.Tjernlund@...inera.com,
        miquel.raynal@...tlin.com, vigneshr@...com, richard@....at,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>
Cc:     Chris Packham <chris.packham@...iedtelesis.co.nz>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>, marek.vasut@...il.com,
        cyrille.pitchen@...ev4u.fr,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [BUG] mtd: cfi_cmdset_0002: write regression since v4.17-rc1

Hi Ahmad-san,

Thanks for your confirmations. Sorry for late to reply.

Could you please try the patch attached to disable the chip_good() 
change as before?
I think this should work for S29GL964N since the chip_ready() is used 
and works as mentioned.

On 2022/02/07 23:28, Ahmad Fatoum wrote:
> Hello Tokunori-san,
>
> On 29.01.22 19:01, Tokunori Ikegami wrote:
>> Hi Ahmad-san,
>>
>> Thanks for your investigation.
>>
>>> 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
>> Which kernel version has been tested about this?
> I last tested with v5.10.30, but I had briefly tried v5.16-rc as well
> when first debugging this issue.
>
> I have rebased onto v5.17-rc2 now and will use that for further tests.
> The same issue with word write forcing is reproducible there as well.
Noted about these.
>
>> Since the buffered writes disabled by 7e4404113686 for S29GL256N and tested on kernel 5.10.16.
>> So I would like to confirm if the issue depended on the CPU or kernel version, etc.
>> Note: The chips S29GL064N and S29GL256N seem different the flash Mb size basically.
> I see. To be extra sure, I have replaced 0x2201 with 0x0c01 to hit
> the same code paths, but no improvement.
I see and check the data sheet as described.
>
>>> Doesn't seem to be a buffered write issue here though as the writes
>>> did work fine before dfeae1073583. Any other ideas?
>> At first I thought the issue is possible to be resolved by using the word write instead of the buffered writes.
>> Now I am thinking to disable the changes dfeae1073583 partially with any condition if possible.
> What seems to work for me is checking if chip_good or chip_ready
> and map_word is equal to 0xFF. I can't justify why this is ok though.
> (Worst case bus is floating at this point of time and Hi-Z is read
> as 0xff on CPU data lines...)

Sorry I am not sure about this.
I thought the chip_ready() itself is correct as implemented as the data 
sheet in the past.
But it did not work correctly so changed to use chip_good() instead as 
it is also correct.

>
>> By the way could you please let me know the chip information for more detail? (For example model number, cycle and device ID, etc.)
> I can't read it off the chip, but vendor uses S29GL064N90FFI02 or S29GL964N11FFI02.
> Kernel reports it with:
> ff800000.flash: Found 1 x16 devices at 0x0 in 8-bit bank. Manufacturer ID 0x000001 Chip ID 0x000c01
The change attached checks the device ID 0x0c01 and use chip_ready() 
instead on chip_good().
>
> I am not sure what you mean with cycle. If you tell me what
> command to run, I can paste the output.
Sorry my understanding was not correct about the data sheet description 
device ID and cycle.

Regards,
Ikegami

>
> Thanks,
> 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@...t:~# 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.
>>>>>>
>
View attachment "0001-mtd-cfi_cmdset_0002-Use-chip_ready-for-write-on-S29G.patch" of type "text/plain" (7494 bytes)

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