N25Q256A 13E40

[Brian Norris]

Hi Marek,

On Fri, Oct 11, 2013 at 6:17 PM, Marek Vasut <marex at denx.de> wrote:

>> 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 at 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.
>
> I wish I had such a bootrom. In my case (freescale imx28), the bootrom can just
> do 3-byte operation and that's it. I believe the only way around here is to
> power-cycle the spi flash before the bootrom starts using it.

Well, such is life when dealing with these flash. Manufacturers
apparently didn't understand the impact that adding incompatible
mode-switches to such fundamental commands would have :(

>> > > [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?
>
> Urgh, I just noticed I did exactly this. I modified the driver to enable this 4-
> byte opcodes and then just forgot about it. Pardon my stupidity :(

No problem. The manufacturers haven't made this an easy problem.

Brian