Message-ID: <7c2c6d22-399b-42e7-8ac7-098f036e9e81@broadcom.com>
Date: Tue, 20 Aug 2024 11:53:41 +0200
From: Arend van Spriel <arend.vanspriel@...adcom.com>
To: Sebastian Reichel <sebastian.reichel@...labora.com>
Cc: jacobe.zang@...ion.com, bhelgaas@...gle.com,
 brcm80211-dev-list.pdl@...adcom.com, brcm80211@...ts.linux.dev,
 christophe.jaillet@...adoo.fr, conor+dt@...nel.org, davem@...emloft.net,
 devicetree@...r.kernel.org, duoming@....edu.cn, edumazet@...gle.com,
 gregkh@...uxfoundation.org, krzk+dt@...nel.org, kuba@...nel.org,
 kvalo@...nel.org, linux-kernel@...r.kernel.org,
 linux-wireless@...r.kernel.org, megi@....cz, minipli@...ecurity.net,
 netdev@...r.kernel.org, pabeni@...hat.com, robh@...nel.org,
 saikrishnag@...vell.com, stern@...land.harvard.edu, yajun.deng@...ux.dev
Subject: Re: [PATCH v11 0/4] Add AP6275P wireless support

On 8/19/2024 10:33 PM, Sebastian Reichel wrote:
> Hello,
> 
> On Mon, Aug 19, 2024 at 09:35:12PM GMT, Arend van Spriel wrote:
>> On 8/19/2024 6:42 PM, Sebastian Reichel wrote:
>>> I tested this on RK3588 EVB1 and the driver is working fine. The DT
>>> bindings are not correct, though:
>>>
>>> linux/arch/arm64/boot/dts/rockchip/rk3588-evb1-v10.dtb: wifi@0,0:
>>> compatible: 'oneOf' conditional failed, one must be fixed:
>>>
>>> ['pci14e4,449d', 'brcm,bcm4329-fmac'] is too long
>>> 'pci14e4,449d' is not one of ['brcm,bcm43143-fmac', 'brcm,bcm4341b0-fmac',
>>> 'brcm,bcm4341b4-fmac', 'brcm,bcm4341b5-fmac', 'brcm,bcm4329-fmac',
>>> 'brcm,bcm4330-fmac', 'brcm,bcm4334-fmac', 'brcm,bcm43340-fmac',
>>> 'brcm,bcm4335-fmac', 'brcm,bcm43362-fmac', 'brcm,bcm4339-fmac',
>>> 'brcm,bcm43430a0-fmac', 'brcm,bcm43430a1-fmac', 'brcm,bcm43455-fmac',
>>> 'brcm,bcm43456-fmac', 'brcm,bcm4354-fmac', 'brcm,bcm4356-fmac',
>>> 'brcm,bcm4359-fmac', 'brcm,bcm4366-fmac', 'cypress,cyw4373-fmac',
>>> 'cypress,cyw43012-fmac', 'infineon,cyw43439-fmac']
>>> from schema $id: http://devicetree.org/schemas/net/wireless/brcm,bcm4329-fmac.yaml#
>>>
>>> It's easy to see the problem in the binding. It does not expect a
>>> fallback string after the PCI ID based compatible. Either the
>>> pci14e4,449d entry must be added to the first enum in the binding,
>>> which has the fallback compatible, or the fallback compatible
>>> should not be added to DTS.
>>
>> Never understood why we ended up with such a large list. When the binding
>> was introduced there was one compatible, ie. brcm,bcm4329-fmac. People
>> wanted all the other flavors because it described a specific wifi chip and
>> no other reason whatsoever. The PCI ID based compatible do obfuscate that
>> info so those are even less useful in my opinion.
>>
>>> If the fallback compatible is missing in DTS, the compatible check in
>>> brcmf_of_probe() fails and the lpo clock is not requested resulting
>>> in the firmware startup failing. So that would require further
>>> driver changes.
>>
>> Right. The text based bindings file in 5.12 kernel clearly says:
>>
>> Required properties:
>>
>>   - compatible : Should be "brcm,bcm4329-fmac".
>>
>> In 5.13 kernel this was replaced by the json-schema yaml file. The PCI ID
>> based enum which was added later does also list brcm,bcm4329-fmac so why
>> does that not work for the compatible list ['pci14e4,449d',
>> 'brcm,bcm4329-fmac']? Looking at the compatible property in yaml which I
>> stripped a bit for brevity:
>>
>> properties:
>>    compatible:
>>      oneOf:
>>        - items:
>>            - enum:
>>                - brcm,bcm43143-fmac
>>                - brcm,bcm4329-fmac
>>                - infineon,cyw43439-fmac
>>            - const: brcm,bcm4329-fmac
>>        - enum:
>>            - brcm,bcm4329-fmac
>>            - pci14e4,43dc  # BCM4355
>>            - pci14e4,4464  # BCM4364
>>            - pci14e4,4488  # BCM4377
>>            - pci14e4,4425  # BCM4378
>>            - pci14e4,4433  # BCM4387
>>
>> So how should I read this. Searching for some sort of syntax description I
>> found [1] which has an example schema with description that has a similarly
>> complicated compatible property. From that I think the above should be
>> changed to:
>>
>>   properties:
>>     compatible:
>>       oneOf:
>>         - items:
>>             - enum:
>>                 - brcm,bcm43143-fmac
>> -              - brcm,bcm4329-fmac
>>                 - infineon,cyw43439-fmac
>>             - const: brcm,bcm4329-fmac
>> +      - items:
>>             - enum:
>> -              - brcm,bcm4329-fmac
>>                 - pci14e4,43dc  # BCM4355
>>                 - pci14e4,4464  # BCM4364
>>                 - pci14e4,4488  # BCM4377
>>                 - pci14e4,4425  # BCM4378
>>                 - pci14e4,4433  # BCM4387
>> +          - const: brcm,bcm4329-fmac
>> +      - const: brcm,bcm4329-fmac
>>
>> This poses a constraint in which the last string in the compatible list is
>> always 'brcm,bcm4329-fmac' even if it is the only string. At least that is
>> my understanding so if my understanding is wrong feel free to correct me on
>> this.
>>
>> [1] https://docs.kernel.org/devicetree/bindings/writing-schema.html
> 
> Your proposed change should work as you describe. But it will result
> in DT check errors for some Apple devices, which followed the
> current binding and do not have the "brcm,bcm4329-fmac" fallback
> compatible:
> 
> $ git grep -E "(pci14e4,43dc)|(pci14e4,4464)|(pci14e4,4488)|(pci14e4,4425)|(pci14e4,4433)" arch/
> arch/arm64/boot/dts/apple/t8103-jxxx.dtsi:           compatible = "pci14e4,4425";
> arch/arm64/boot/dts/apple/t8112-j413.dts:            compatible = "pci14e4,4433";
> arch/arm64/boot/dts/apple/t8112-j493.dts:            compatible = "pci14e4,4425";

> I guess patch 3/4 from this series will also introduce some
> regressions for these devices by moving the check. What is the
> purpose of the compatible check in brcmf_of_probe() in the first
> place? Can it just be dropped?
> 
> I see it was introduced 10 years ago in 61f663dfc1a09, probably to
> avoid a spurious error message for systems not having the IRQ
> described in DT? The current code exits quietly when none of the
> optional resources are defined.

It was introduced simply because the compatible property has a meaning 
that goes beyond informational. It is a claim that the properties of the 
node comply to the bindings specification. I would really want to keep 
the sanity check event though all properties are optional. The 
constraint keeps the compatible matching in the driver relatively simple.

Regards,
Arend

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