linux-kernel - Re: [PATCH 2/5] dt-bindings: nvmem: Convert xlnx,zynqmp-nvmem.txt to yaml

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Message-ID: <209334cd-c922-4bd6-b116-83297c7e8b79@linaro.org>
Date:   Fri, 13 Oct 2023 14:54:34 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Michal Simek <michal.simek@....com>,
        Praveen Teja Kundanala <praveen.teja.kundanala@....com>,
        srinivas.kandagatla@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] dt-bindings: nvmem: Convert xlnx,zynqmp-nvmem.txt to
 yaml

On 13/10/2023 14:08, Michal Simek wrote:
> 
> 
> On 10/13/23 13:58, Krzysztof Kozlowski wrote:
>> On 13/10/2023 13:51, Michal Simek wrote:
>>>
>>>
>>> On 10/13/23 13:46, Krzysztof Kozlowski wrote:
>>>> On 13/10/2023 13:22, Michal Simek wrote:
>>>>>>
>>>>>>> +
>>>>>>> +required:
>>>>>>> +  - compatible
>>>>>>
>>>>>> required: block goes after patternProperties: block
>>>>>>
>>>>>>> +
>>>>>>> +patternProperties:
>>>>>>> +  "^soc_revision@0$":
>>>>>>
>>>>>> Why do you define individual memory cells? Is this part of a binding?
>>>>>> IOW, OS/Linux requires this?
>>>>>
>>>>> nvmem has in kernel interface where you can reference to nodes. nvmem_cell_get()
>>>>> calls. It means you should be able to describe internal layout that's why names
>>>>> are used. And address in name is there because of reg property is used to
>>>>> describe base offset and size.
>>>>
>>>> That's not really what I am asking. Why internal layout of memory must
>>>> be part of the bindings?
>>>
>>> It doesn't need to be but offsets are hardcoded inside the driver itself and
>>> they can't be different.
>>
>> Hm, where? I opened drivers/nvmem/zynqmp_nvmem.c and I do not see any
>> hard-coded offsets.
> 
> Current driver supports only soc revision from offset 0.
> But if you look at 5/5 you need to define offsets where information is present.
> +#define SOC_VERSION_OFFSET	0x0
> +#define EFUSE_START_OFFSET	0xC
> +#define EFUSE_END_OFFSET	0xFC
> +#define EFUSE_PUF_START_OFFSET	0x100
> +#define EFUSE_PUF_MID_OFFSET	0x140
> +#define EFUSE_PUF_END_OFFSET	0x17F

There is nothing like this in existing driver, so the argument that "I
am adding this to the binding during conversion because driver needs it"
is not true. Conversion is only a conversion.

Now, if you want to add something new to the binding because of new
driver changes, that's separate topic.

And since it is new change in the driver I can comment: please don't.
Your nvmem driver should not depend on it. nvmem is only the provider.

Best regards,
Krzysztof