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: <D890I4EPARNO.O0VS9VZUL6IR@kernel.org>
Date: Thu, 06 Mar 2025 08:41:17 +0100
From: "Michael Walle" <mwalle@...nel.org>
To: <Manikandan.M@...rochip.com>, <miquel.raynal@...tlin.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>, <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@...rochip.com>
Subject: Re: [PATCH 1/2] mtd: spi-nor: sst: register SFDP region into NVMEM
 framework to read MAC Address

Hi,

> >> 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?
> > 
> 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.

Why didn't you mention that this is a vendor table in the commit
message?

Anyway, please write proper support in the core for parsing vendor
tables and exposing them as a nvmem device if needed (and asked to
do so by the driver of course).

-michael