Hi Hunter
On Fri, Feb 10, 2017 at 8:57 AM, Hunter Somerville <
hsomervi5790@gmail.com>
wrote:
> On Tue, Feb 7, 2017 at 3:44 PM, Charles Manning <cdhmanning@gmail.com>
> wrote:
>
>>
>>
>> On Tue, Feb 7, 2017 at 5:19 AM, Hunter Somerville <hsomervi5790@gmail.com
>> > wrote:
>>
>>> Hello,
>>>
>>> We are encountering an issue where we will usually lose an entire
>>> partition of data if the flash device loses power during a write operation.
>>> When we bring the system back up and remount, all files/directories appear
>>> as long strings of questionmarks with incorrect filenames and such, and we
>>> end up having to flash erase the partition to recover. This only happens on
>>> the device with fairly large pages (4MB Erase blocks, 32KB pages, 1KB OOB),
>>> and does not occur on the more typical device in the same system which uses
>>> 4KB pages.
>>>
>>
>> What kind of flash are you using? What part number?
>>
>
> The hardware is proprietary, and not designed by us. What I can tell you
> is that we interface with an FPGA - not the flash chips directly. The FPGA
> performs the writes.
>
Surely the flash parts are off the shelf.
>
>
>>
>>> Obviously these devices utilize different drivers and different
>>> hardware, so the cause might have nothing to do with YAFFS2. However, while
>>> we investigate other possible causes, we felt it might be worthwhile to ask
>>> if anyone else has seen this problem with YAFFS2 or if it could feasibly be
>>> related to the comparably very large page size.
>>>
>>
>> People have used Yaffs with far larger page sizes than that.
>>
>
> Great. This was my biggest questionmark on the Yaffs side of the problem.
>
>
>> This sounds to me like some sort of driver side issue.
>>
>> What OS are you using?
>>
>
> Linux 3.12. Our driver uses DMA. Worth noting that we never see any
> problems when shutting down normally or even after an abrupt power loss
> when NOT actively writing. This problem only occurs when we cut power
> during a write operation.
>
>
>>
>> Those questionmarks are probably 0xFF characters.
>>
> One way to debug this is to do binary dumps of the flash and look to see
>> if they make any sense. It is often better to work with a small partition
>> for test purposes just to reduce the amount of info you are working with
>> (eg, maybe 20 blocks).
>>
>
> I tried to do this today - interestingly, after moving my testing to a
> smaller ~1.6GB partition lower in the devices address range, I was
> completely unable to make it fail. I can only cause this failure in the
> much larger partition. I decided instead to just use smaller files after a
> fresh flash erase and try to keep my work in the first 30 blocks of the
> large partition. This led me to discover that, indeed, the questionmarks
> are 0xFF characters. I did nanddumps before the power loss, after the power
> loss but before remounting, and after remounting. The before/after dumps
> were identical, but the nanddump after mounting showed that the first 30
> blocks had all been erased. I'm investigating the cause of this.
>
> Thank you for your assistance,
> Hunter Somerville
>
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