Re: [PATCH v4 1/7] dt-bindings: mtd: jedec,spi-nor: allow the SFDP to be exposed via NVMEM

[<Manikandan.M@microchip.com>]

Hi Krzysztof,

On 7/2/26 11:46 AM, Krzysztof Kozlowski wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On Tue, Jun 30, 2026 at 02:54:00PM +0530, Manikandan Muralidharan wrote:
>> Add an optional "sfdp" child node (compatible "jedec,sfdp") that
>> describes the SFDP as a read-only NVMEM provider via nvmem.yaml, so its
> 
> What is SFDP?
> 
SFDP is the Serial Flash Discoverable Parameters -- a JEDEC-standardised
(JESD216) read-only parameter table present in most SPI NOR flashes, the 
table contents provide basic information about the flash. There are 
standard tables which are specified by the JEDEC standard and there are 
vendor tables.
>> contents (e.g. a vendor EUI-48/EUI-64) can be read through NVMEM cells.
>>
>> Signed-off-by: Manikandan Muralidharan <manikandan.m@microchip.com>
>> ---
>>   .../devicetree/bindings/mtd/jedec,spi-nor.yaml | 18 ++++++++++++++++++
>>   1 file changed, 18 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
>> index 587af4968255..98fd954598ab 100644
>> --- a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
>> +++ b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml
>> @@ -103,6 +103,20 @@ properties:
>>     spi-cpol: true
>>     spi-cpha: true
>>
>> +  sfdp:
>> +    $ref: /schemas/nvmem/nvmem.yaml#
>> +    unevaluatedProperties: false
>> +    description:
>> +      The Serial Flash Discoverable Parameters (SFDP) tables exposed as a
>> +      read-only NVMEM device. This allows standard or vendor-specific SFDP
>> +      data (for example a factory-programmed EUI-48/EUI-64 identifier) to be
>> +      consumed through NVMEM cells.
>> +    properties:
>> +      compatible:
>> +        const: jedec,sfdp
>> +    required:
>> +      - compatible
> 
> Where are any resources? What sort of sub-device is represented here by
> an empty device node?
The sub-device describes the flash's SFDP region exposed as a read-only 
NVMEM provider:the SPI NOR core reads the SFDP and registers it as an 
NVMEM device rooted at this node.Its contents are then consumed through 
NVMEM cells -- a "fixed-layout" for data at a known offset, or an 
"nvmem-layout" parser for data whose location must be discovered at 
runtime (the Microchip EUI layout driver in patch 4/7 does the latter).
It is not a bus-addressed hardware sub-device, so it has no reg.

This models the SFDP-as-NVMEM approach suggested during the v3 review, 
instead of special-casing the vendor table in the SPI NOR core:

https://lore.kernel.org/linux-arm-kernel/20250521070336.402202-1-manikandan.m@microchip.com/
> 
> Best regards,
> Krzysztof
> 


-- 
Thanks and Regards,
Manikandan M.