[PATCH] mtd: cfi_cmdset_0001 - fixup for PC28F512P33TFA

[Christian Riesch]

Hi,

--On April 02, 2014 09:25 +0200 Joakim Tjernlund 
<joakim.tjernlund at transmode.se> wrote:

> Christoph Fritz <chf.fritz at googlemail.com> wrote on 2014/04/02 01:10:30:
>>
>> On Tue, 2014-04-01 at 21:13 +0200, Joakim Tjernlund wrote:
>> > Christoph Fritz <chf.fritz at googlemail.com> wrote on 2014/04/01
> 17:09:51:
>> > > I already tried all sorts of combinations of various delays and 0xff
>> > > writes, which can be used wasteful without impact. And yes, errors
> are

There are similar issues with the Micron M29EW that uses the 
cfi_cmdset_0002.c driver. See TN-13-07 [1]. The fixes required by this 
technical note were added to the driver in commit 
420962884379bd434a7f643d0936281b2ab4b30c. Since the fixes are pretty 
similar to those in TN-12-06, I think you should have a look that this 
commit, in case you didn't already.

Which delays did you try? Did you try the maximum delay of 500us? For the 
M29EW, 20us worked fine at room temperature, but at -40°C 500us much 
larger delays were required, therefore we set it to 500us finally.

[1] 
http://www.micron.com/-/media/Documents/Products/Technical%20Note/NOR%20Flash/tn1307_patching_linux_kernel_for_m29.pdf

>> > > happening less -- but are still happening (at for example -2°C
> starting
>> > > udev or a filesys-bench program like bonnie++).
>> >
>> > Amazing Micron still sells these defect chips
>>
>> Yeah, and it was pain to do all these kinds of tests to get it reliably
>> working for a real world application where minus degrees can happen. For
>> me it would be no problem to keep this quirk in my private queue, but
>> involving a bigger audience seems to be right considering the facts.
>>
>> > > Sure, it's possible that I missed the holy right
>> > > delay-0xff-quirk-combination to get this NOR flash reliable working
> for
>> > > its specified temperature range. But until nobody has found it, I
> would

After reading TN-12-06 I guess the correct order should be

1) 0xff
2) the existing 0xd0/0x70
3) wait 500us

right? Could you send a patch of the combination you tried (and that did 
not work) for discussion?

[...]

>> > > Maybe someone from Micron can help?
>> >
>> > Yes, you should contact them.
>>
>> Is there anybody out there knowing a contact without the need of going
>> through a business-ticket-support-hell ?

Christoph, see private mail.

Regards, Christian