linux-kernel - Re: [PATCH v2 01/13] spi: dt-bindings: cdns,qspi-nor: Add Renesas RZ/N1D400 to the list

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Message-ID: <87ms27qmgj.fsf@bootlin.com>
Date: Wed, 21 Jan 2026 11:39:08 +0100
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Rob Herring <robh@...nel.org>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>,  Mark Brown
 <broonie@...nel.org>,  Krzysztof Kozlowski <krzk+dt@...nel.org>,  Conor
 Dooley <conor+dt@...nel.org>,  Geert Uytterhoeven
 <geert+renesas@...der.be>,  Magnus Damm <magnus.damm@...il.com>,  Vaishnav
 Achath <vaishnav.a@...com>,  Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>,  Hervé Codina
 <herve.codina@...tlin.com>,
  Wolfram Sang <wsa+renesas@...g-engineering.com>,  Vignesh Raghavendra
 <vigneshr@...com>,  Santhosh Kumar K <s-k6@...com>,  Pratyush Yadav
 <pratyush@...nel.org>,  Pascal Eberhard <pascal.eberhard@...com>,
  linux-spi@...r.kernel.org,  devicetree@...r.kernel.org,
  linux-kernel@...r.kernel.org,  linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v2 01/13] spi: dt-bindings: cdns,qspi-nor: Add Renesas
 RZ/N1D400 to the list


>> >> +      - items:
>> >> +          - const: renesas,r9a06g032-qspi
>> >> +          - const: renesas,rzn1-qspi
>> >> +          - const: cdns,qspi-nor
>> >
>> > Doesn't the need for (at least) the CQSPI_NO_INDIRECT_MODE flag mean
>> > that this device is not compatible with cdns,qspi-nor, and thus the
>> > cdns,qspi-nor fallback must not be used?
>> 
>> I understand the question. It is true that I use driver data to limit
>> the number of features the IP can use and this data is associated to the
>> Renesas compatible, but I believe all other flavours of this IP would
>> also not work without driver data attached to their front
>> compatible. None of the SoCs with the Cadence QSPI IP actually would run
>> without their own driver data. For me the fallback compatible is
>> relevant because it describes the hardware as "this is a derivative of
>> the Cadence controller" (and it is clearly the case, and this is also
>> mentioned in the reference manual), even though I agree using
>> cdns,qspi-nor would definitely not work alone. But again, none of the
>> other flavours would anyway.
>
> Fallbacks should be usable on their own. We've generally moved away from 
> having these generic licensed IP compatibles because they always have 
> per platform changes.

Thanks for settling my doubts. I will drop the cdns,qspi-nor then.

Miquèl