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

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Message-ID: <87ikonydym.fsf@bootlin.com>
Date: Wed, 05 Mar 2025 11:22:09 +0100
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Manikandan Muralidharan <manikandan.m@...rochip.com>
Cc: <robh@...nel.org>,  <krzk+dt@...nel.org>,  <conor+dt@...nel.org>,
  <nicolas.ferre@...rochip.com>,  <alexandre.belloni@...tlin.com>,
  <claudiu.beznea@...on.dev>,  <tudor.ambarus@...aro.org>,
  <pratyush@...nel.org>,  <mwalle@...nel.org>,  <richard@....at>,
  <vigneshr@...com>,  <devicetree@...r.kernel.org>,
  <linux-arm-kernel@...ts.infradead.org>,  <linux-kernel@...r.kernel.org>,
  <linux-mtd@...ts.infradead.org>,  Varshini Rajendran
 <varshini.rajendran@...rochip.com>
Subject: Re: [PATCH 1/2] mtd: spi-nor: sst: register SFDP region into NVMEM
 framework to read MAC Address

On 05/03/2025 at 15:31:33 +0530, Manikandan Muralidharan <manikandan.m@...rochip.com> wrote:

> From: Varshini Rajendran <varshini.rajendran@...rochip.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?

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