Re: N25Q256A 13E40

[Brian Norris <computersforpeace@gmail.com>]

Hi,

On Wed, Oct 09, 2013 at 12:14:02PM +0200, Marek Vasut wrote:
> > On Mon, Oct 7, 2013 at 9:24 AM, Marek Vasut <marex@denx.de> wrote:
> > > Let's talk about our favourite chip :) I just got my hands on N25Q256A .
> > > Since there was quite a flurry of patches for this and similar chips and
> > > I got it working on a different chip with exactly the same IDs and type,
> > > I'd would expect linux to work with this one too. Guess what ... ;-)
> > > 
> > > This particular incarnation of N25Q256A completely ignores the 4-byte
> > > ERASE (0xdc) command. Apparently, if I look closely, it's N25Q256A 13E40
> > > variant and seeing the Note #14 (datasheet page 30 / below Table 18.
> > > Command set), quoting:
> > > 
> > > 14.This command is only for part numbers N25Q256A83ESF40x and
> > > N25Q256A83E1240x.
> > 
> > This note also applies to PAGE_PROGRAM_4B (0x12) as well, right?
> 
> Yeah, both ERASE_4B and PP_4B or whatever they're called there. Interestingly 
> enough, READ_4B works ;-/

Well, the READ_4B consistency is (unintentionally?) helpful for my
systems, as we have begun implementing a jumper switch so that the boot
ROM will know whether to use FAST_READ or FAST_READ_4B. Since
essentially all large SPI flash at *least* support the READ_4B command
(as you noted), we can reliably boot from the flash, no matter what mode
it is left in. After booting, we can choose the appropriate mode for
programming/erasing.

> > [Now that I went back to look at some more code:] Wait, but we don't
> > even try to use the 4-byte dedicated commands like 0xdc on Micron
> > flash, so why are you having this problem? The code currently stands
> > as:
> 
> The JEDEC_MFR for this flash Micron N25Q256A is CFI_MFR_ST (I wonder why).

Probably some series of acquisitions?

But you didn't quite answer my question. Are you having problems with
this Micron/ST/something-that's-not-AMD-or-Spansion flash using the
current mainline? Or did you only have trouble when you tried modifying
the code to use the dedicated 4-byte addressing commands?

> >   if (JEDEC_MFR(info->jedec_id) == CFI_MFR_AMD) {
> >           /* Dedicated 4-byte command set */
> >           ...

Brian