linux-kernel - Re: [PATCH v3 2/5] dt-bindings: mips: mips-cm: Add a new compatible string for EyeQ6

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Message-Id: <bf08785b-9963-4539-92ef-b73c3abe8c19@app.fastmail.com>
Date: Tue, 28 Jan 2025 01:16:20 +0000
From: "Jiaxun Yang" <jiaxun.yang@...goat.com>
To: "Rob Herring" <robh@...nel.org>
Cc: "Gregory CLEMENT" <gregory.clement@...tlin.com>,
 "Aleksandar Rikalo" <arikalo@...il.com>,
 "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>,
 "Krzysztof Kozlowski" <krzk+dt@...nel.org>,
 "Conor Dooley" <conor+dt@...nel.org>,
 "Vladimir Kondratiev" <vladimir.kondratiev@...ileye.com>,
 Théo Lebrun <theo.lebrun@...tlin.com>,
 "Tawfik Bayouk" <tawfik.bayouk@...ileye.com>,
 "Thomas Petazzoni" <thomas.petazzoni@...tlin.com>,
 "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/5] dt-bindings: mips: mips-cm: Add a new compatible string for
 EyeQ6



在2025年1月27日一月 下午10:07，Rob Herring写道：
> On Mon, Jan 27, 2025 at 3:43 PM Jiaxun Yang <jiaxun.yang@...goat.com> wrote:
>>
>>
>>
>> 在2025年1月23日一月 上午11:01，Gregory CLEMENT写道：
>> > The CM3.5 used on EyeQ6 reports that Hardware Cache Initialization is
>> > complete, but in reality it's not the case. It also incorrectly
>> > indicates that Hardware Cache Initialization is supported. This new
>> > compatible string allows warning about this broken feature that cannot
>> > be detected at runtime.
>> >
>> > Signed-off-by: Gregory CLEMENT <gregory.clement@...tlin.com>
>> > ---
>> >  Documentation/devicetree/bindings/mips/mti,mips-cm.yaml | 12 +++++++++++-
>> >  1 file changed, 11 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/Documentation/devicetree/bindings/mips/mti,mips-cm.yaml
>> > b/Documentation/devicetree/bindings/mips/mti,mips-cm.yaml
>> > index
>> > 4324b2306535f1bf66c44b1f96be9094ee282041..d129d6382847768dc026336d8d2c7328b6b81f9b
>> > 100644
>> > --- a/Documentation/devicetree/bindings/mips/mti,mips-cm.yaml
>> > +++ b/Documentation/devicetree/bindings/mips/mti,mips-cm.yaml
>> > @@ -19,7 +19,12 @@ maintainers:
>> >
>> >  properties:
>> >    compatible:
>> > -    const: mti,mips-cm
>> > +    oneOf:
>> > +      - const: mti,mips-cm
>> > +      - const: mobileye,eyeq6-cm
>> > +        description:
>> > +          On EyeQ6 the HCI (Hardware Cache Initialization) information for
>> > +          the L2 cache in multi-cluster configuration is broken.
>> >
>> >    reg:
>> >      description:
>> > @@ -44,4 +49,9 @@ examples:
>> >        compatible = "mti,mips-cm";
>> >        reg = <0x1bde8000 0x8000>;
>> >      };
>> > +
>> > +  - |
>> > +    coherency-manager {
>> > +      compatible = "mobileye,eyeq6-cm";
>>
>> I think “mobileye,eyeq6-cm”, “mti,mips-cm” would describe the hardware better as eyeq6’s CM is just a special variant of mips-cm.
>
> Is s/w that only understands “mti,mips-cm” useful on eyeq6 chip? If
> so, I agree. If not, then a fallback compatible is not useful.

Yes, mobileye,eyeq6-cm only enable an additional bug workaround in software.

The programming interfaces and so on remains unchanged.

Also other firmware components like U-Boot doesn’t need to be aware of eyeq6 variant.

Thanks

>
> Rob

-- 
- Jiaxun