[PATCH v4 0/7] Read MAC address from SST vendor specific SFDP region

[Manikandan Muralidharan]

Some Microchip/SST QSPI flashes (e.g. the SST26VF064BEUI) are factory
programmed with globally unique, write-protected EUI-48 and EUI-64
identifiers stored in a vendor-specific SFDP parameter table. On boards
that have no on-board EEPROM (sama5d27_wlsom1, sama5d29 curiosity,
sam9x75 curiosity) this is a reliable source for an Ethernet MAC address,
instead of relying on a U-Boot-provided or random address.

This v4 reworks the approach into a generic NVMEM framework with no vendor
code in the SPI NOR core:
 - The SPI NOR core now exposes the entire SFDP as a generic read-only
   NVMEM device, rooted at a new "sfdp" child node of the flash.
 - A new NVMEM layout driver (drivers/nvmem/layouts/) locates the
   Microchip vendor parameter table at runtime and presents the EUI-48 as
   a "mac-address" cell.
 - Arbitrary parameters can be read with a standard fixed-layout
   (known offset) or with an nvmem-layout parser (location discovered at runtime).

Changes in v4:
 - Rework per v3 review: remove the vendor-specific SFDP handling from the
   SPI NOR core; expose the whole SFDP as a generic read-only NVMEM device
   and move the EUI extraction into an nvmem-layout driver.
 - Introduce a new nvmem-layout driver to discover the vendor-table location
   at runtime; no offset hardcoded in the device tree.
 - Describe the SFDP via a dedicated "sfdp" subnode (compatible
   "jedec,sfdp"), which also resolves the v3 dtbs_check "Unevaluated
   properties ('nvmem-layout')" warning.
 - Reverse the stored EUI bytes into canonical MAC order.
 - Enable the layout in sama5_defconfig.

 Changes in v3:
 - 2/3 - add support to update the QSPI partition into 'fixed-partition'
   binding in sama5d27_wlsom1
 - 3/3 - add nvmem-layout in qspi node for EUI48 MAC Address and nvmem cell
   properties for macb node in sama5d27_wlsom1

Changes in v2:
 - 1/3 - parse the SST vendor table, read and store the addresses
  into a resource - managed space. Register the addresses
  into NVMEM framework
 - 2/3 - add support to update the QSPI partition into 'fixed-partition'
  binding

v3: https://lore.kernel.org/linux-arm-kernel/20250521070336.402202-1-manikandan.m@xxxxxxxxxxxxx/

Manikandan Muralidharan (7):
  dt-bindings: mtd: jedec,spi-nor: allow the SFDP to be exposed via
    NVMEM
  dt-bindings: nvmem: layouts: add Microchip/SST SFDP EUI layout
  mtd: spi-nor: sfdp: expose the SFDP as a read-only NVMEM device
  nvmem: layouts: add Microchip/SST SFDP EUI layout driver
  ARM: dts: microchip: sama5d27_wlsom1: use fixed-partitions for QSPI
    flash
  ARM: dts: microchip: sama5d27_wlsom1: read MAC address from QSPI SFDP
  ARM: configs: sama5: enable Microchip/SST SFDP EUI NVMEM layout

 .../bindings/mtd/jedec,spi-nor.yaml           |  18 ++
 .../layouts/microchip,sst26vf-sfdp-eui.yaml   |  60 ++++++
 .../bindings/nvmem/layouts/nvmem-layout.yaml  |   1 +
 MAINTAINERS                                   |   6 +
 .../dts/microchip/at91-sama5d27_wlsom1.dtsi   |  61 +++---
 .../dts/microchip/at91-sama5d27_wlsom1_ek.dts |   2 +
 arch/arm/configs/sama5_defconfig              |   1 +
 drivers/mtd/spi-nor/core.c                    |   5 +
 drivers/mtd/spi-nor/core.h                    |   1 +
 drivers/mtd/spi-nor/sfdp.c                    |  83 ++++++++
 drivers/nvmem/layouts/Kconfig                 |  10 +
 drivers/nvmem/layouts/Makefile                |   1 +
 drivers/nvmem/layouts/sst26vf-sfdp-eui.c      | 182 ++++++++++++++++++
 13 files changed, 409 insertions(+), 22 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/nvmem/layouts/microchip,sst26vf-sfdp-eui.yaml
 create mode 100644 drivers/nvmem/layouts/sst26vf-sfdp-eui.c


base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
-- 
2.43.0