[PATCH] mtd: spi-nor: Enable stateless 4-byte opcodes for N25Q256A/N25Q512A/N25Q00

[Alexander Sverdlin]

Hello Cyrille,

On 16/10/17 23:27, Cyrille Pitchen wrote:
> Hi Alexander,
> 
> Le 16/10/2017 à 14:25, Alexander Sverdlin a écrit :
>> Hello Marek,
>>
>> On 16/10/17 13:35, Marek Vasut wrote:
>>>> The datasheets explicitly state that the stateless opcodes are supported
>>>> and that they "do not need to be set up in the addressing mode".
>>>>
> 
> I don't totally agree. Micron memories have a little quirk: if you look
> closely at their datasheets (currently reading the N25Q512A datasheet)
> the 12h op code doesn't always work as expected.
> 
> For some memory parts, the 12h op code is used for 4-byte address Page
> Program 1-1-1 (as it should) whereas for other memory parts, this very
> same op code means 3-byte address Page Program x-4-4 (non standard
> usage, should have been 38h/3Eh).
> 
> See note 18:
> """
> The code 38h is valid only for part numbers N25Q512A83GSF40x,
> N25Q512A83G1240x,
> N25Q512A83GSFA0x, N25Q512A83G12A0x and N25Q512A83G12H0x; the code 12h is
> valid for the other part numbers
> """
> 
> Also about the 4-byte address Page Program 1-1-1 and 1-1-4, see note 17:
> """
> Only available for part numbers N25Q512A83GSF40x, N25Q512A83G1240x,
> N25Q512A83GSFA0x, N25Q512A83G12A0x and N25Q512A83G12H0x
> """
> 
> So even with the basic Page Program 1-1-1, this patch would introduce
> regressions with some memory parts.
> 
> This is a known issue of Micron memories and this is why the
> SPI_NOR_4B_OPCODES flag was not set before for those memories!

yes, you are right, while 256/512Mbit variants just potentially have some
non-standard variations, in N25Q00AA series 12h command has non-standard
mapping in all parts. 

Seems, we have to just scrap this patch.

-- 
Best regards,
Alexander Sverdlin.