Re: [PATCH] mtd: cfi_cmdset_0001 - fixup for PC28F512P33TFA

[Christoph Fritz <chf.fritz@googlemail.com>]

On Tue, 2014-04-01 at 21:13 +0200, Joakim Tjernlund wrote:
> Christoph Fritz <chf.fritz@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
> > 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
> > prefer to stick to my posted quirk and just disable suspend erase.
> 
> Problem is, if you add that quirk no-one will be able to remove it later 
> so we
> better make sure there isn't a less intrusive solution.

What about a comment or printk which makes that clear? I anyway don't
think that there are interested users of this specific NOR flash left
using a current kernel -- but who knows, right.

> hmm, have you checked you bus timing? Perhaps you need to relax it 
> somewhat.

Sure, I rechecked the WEIM interface (imx35 bus) settings more than
once. I also did testings with most relaxed settings (highest delays
possible). But still, flash errors do occur.

I should mention that a PC28F256P33BFE (a similar 32 MB NOR flash) works
without any quirk in all my testing environments just reliable as it
should be.
 
> > 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 ?

Thanks
  -- Christoph