[U-Boot] [EXT] [PATCH 2/2] spi-nor: spi-nor-ids: Disable SPI_NOR_4B_OPCODES for n25q512* and n25q256*

[Simon Goldschmidt]

Hi Tudor,

On Tue, Sep 24, 2019 at 1:36 PM <Tudor.Ambarus at microchip.com> wrote:
>
> Hi, Simon,
>
> On 09/23/2019 12:30 PM, Simon Goldschmidt wrote:
>
> cut
>
> >>>     > Subject: [EXT] [PATCH 2/2] spi-nor: spi-nor-ids: Disable
> >>>     > SPI_NOR_4B_OPCODES for n25q512* and n25q256*
> >>>     >
> >>>     > Caution: EXT Email
> >>>     >
> >>>     > Not all variants of n25q256* and n25q512* support 4 Byte stateless
> >>>     > addressing opcodes and there is no easy way to discover at runtime
> >>>     whether
> >>>     > the flash supports this feature or not.
> >>>     > Therefore don't set SPI_NOR_4B_OPCODES for these flashes.
> >>>     Hi Vignesh,
> >>>
> >>>     I think it will be good to keep it here and disable this for boards
> >>>     by using not set flag in config
> >>>     Like
> >>>     # SPI_NOR_4B_OPCODES is not set
> >>>
> >>
> >> SPI_NOR_4B_OPCODES is not a config option. Are you suggesting to add
> >> one? config options don't scale well especially when same defconfig is
> >> used for multiple boards that potentially have different flashes
> >>
> >>>
> >>> I'd prefer to take this patch, as this is what Linux does.
> >>
> >> No, this is not what Linux does. There is no opt-in or opt-out option.
> >> Decision to use 4 byte opcode is done at runtime based on flash that's
> >> detected. Either based on info->flags for that part or by parsing SFDP
> >> table. There is no config option of DT option to force 4 byte addressing
> >>
> >>> I think it's better to have an opt-in option. That way, all chips work with the
> >>> default settings (even if that means some chips don't use 4 baste
> >>> opcodes even if they could).
> >>>
> >>
> >> One solution would be to look at SFDP tables of two variants of flash
> >> and see if there are any differences that can be used as a clue.
> >>
> >> Simon,
> >> Could you provide dump of SFDP tables and all the 6 bytes READ ID of the
> >> flash that you have?
> >
> > I have a n251256a with JEDEC ID 20, ba, 19, 10, 44, 00.
>
> Is this a n25q256a or a MT25QL256ABA? We want to check if there are n25q256a
> flashes that have the 6th bit of the Extended Device Id set to one or not.
> According to n25q256a datasheet the bit 6 is reserved (which probably translates
> to being zero), while on MT25QL256ABA is set to one.

Right, this really is a MT25QL256ABA, I guess. I'm not quite familiar with the
print on the housing, sorry. We had both and here, it's probably the MT, not
the nq.

I also wasn't really aware of the differences between those two, sorry.

Regards,
Simon

>
> Cheers,
> ta
>