Re: [PATCH 1/2] mtd: spi-nor: sst: register SFDP region into NVMEM framework to read MAC Address

Manikandan.M
2025-03-06T06:40:14Z

Hi Miquel,

On 05/03/25 3:52 pm, Miquel Raynal wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
> On 05/03/2025 at 15:31:33 +0530, Manikandan Muralidharan <manikandan.m@microchip.com> wrote:
>
>> From: Varshini Rajendran <varshini.rajendran@microchip.com>
>>
>> EUI identifier and the MAC Address of the Ethernet Interface is stored
>> after the SFDP table of contents starting at address 0x260 in the
>> QSPI memory.
>> Register the entire SFDP region read by the spi-nor (nor->sfdp) into the
>> NVMEM framework and read the MAC Address when requested using the nvmem
>> properties in the DT by the net drivers.
>>
>> In kernel the Ethernet MAC address relied on U-Boot env variables or
>> generated a random address, which posed challenges for boards without
>> on-board EEPROMs or with multiple Ethernet ports.
>> This change ensures consistent and reliable MAC address retrieval from QSPI,
>> benefiting boards like the sama5d29 curiosity and sam9x75 curiosity.
>
> Do you mean spi-nor have a programmable area in their SFDP table? Isn't
> this supposed to be a read-only area written once in factory?
>
The SST26VF064BEUI serial quad flash memory is programmed at the factory
with a globally unique address stored in the SFDP vendor
parameter table and it is permanently write-protected.

https://ww1.microchip.com/downloads/aemDocuments/documents/MPD/ProductDocuments/DataSheets/SST26VF064BEUI-Data-Sheet-DS20006138.pdf

> I am not a big fan of exposing the whole SFDP area. I would suggest to
> expose just the MAC address. You can make use of nvmem layout drivers if
> that is needed.
>
> Thanks,
> Miquèl

--
Thanks and Regards,
Manikandan M.