[U-Boot-Users] CFI driver does not verify writes in buffered mode - feature?

[Detlev Zundel]

Hello Tolunay,

> Wolfgang Denk wrote:
>> In message <46422E3E.40703 at orkun.us> you wrote:
>>>> when using the CFI flash driver with CFG_FLASH_USE_BUFFER_WRITE the
>>>> "usual" verification whether the write did indeed happen correctly is
>>>> not done:
>> ...
>>> In the above example you are overwriting the same data. Which is OK
>>> to write without erasing first. You can turn 1 bits to 0 or
>>> re-write the same data without erasing which is OK. The redundant
>>> environment implementation takes advantage of this in U-Boot. This
>>> is not an error.
>>>
>>> Am I missing something?
>>
>> Yes, you do. Detlev wrote different data, and it was not discovered by
>> the CFI driver. Using one of the propriatary flash drivers like on the
>> TQM8xxL will complain...
>
> Yes, in that case we need to fix this! Detlev, do you have a patch
> suggestion?

No sorry, not right now.  This actually turned out to be a problem
during a training that I do right now.  The participants complained
that they copied u-boot images being correct in RAM to flash but they
were corrupt in flash.  It took me a while to figure out what was
going on here.

If I understand the code correctly then we would have to do a buffer
read after a buffer write and compare the data, right?  I am not too
fluent in working with CFI flashes so I would have to look up all
details like can I simply read from flash after the program cycle or
do I have to do things like take it out of command mode etc so I
couldn't come up with a fix "after work".

On the other hand I consider this to be a serious problem so I
brazenly posted it in the hope that someone else might be able to
solve it more quickly.  If this does not happen, I will have to spend
some time on it, but this will not happen this week nor early next
week...

Thanks
  Detlev

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