linux-kernel - Re: [PATCH v3 7/8] dt-bindings: mfd: Add img,boston-platform-regs

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Date: Fri, 21 Jun 2024 16:51:55 +0100
From: "Jiaxun Yang" <jiaxun.yang@...goat.com>
To: "Krzysztof Kozlowski" <krzk@...nel.org>, "Lee Jones" <lee@...nel.org>,
 "Rob Herring" <robh@...nel.org>, "Krzysztof Kozlowski" <krzk+dt@...nel.org>,
 "Conor Dooley" <conor+dt@...nel.org>,
 "paulburton@...nel.org" <paulburton@...nel.org>,
 "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>
Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>
Subject: Re: [PATCH v3 7/8] dt-bindings: mfd: Add img,boston-platform-regs



在2024年6月20日六月 上午7:40，Krzysztof Kozlowski写道：
[...]
>> 
>> Hi Krzysztof,
>> 
>> I believe U-Boot's implementation is correct. As per simple-mfd binding:
>> 
>> ```
>> simple-mfd" - this signifies that the operating system should
>>   consider all subnodes of the MFD device as separate devices akin to how
>>   "simple-bus" indicates when to see subnodes as children for a simple
>>   memory-mapped bus.
>> ```
>> 
>> This reads to me as "if you want sub nodes to be populated as devices
>> you need this."
>> 
>> In our case there are "clock" and "reset" node sub nodes which should be
>> probed as regular device, so it's true for us.
>
> No, you already got comment from Rob.
>
> Your children depend on parent to provide IO address, so this is not
> simple-mfd. Rule for simple-mfd is that children do not rely on parent
> at all.
>
Hi Krzysztof,

Sorry but can I ask for clarification on "depend on parent to provide IO
address", do you mind explaining it a little bit? Does it mean children
should get regmap node from a phandle property, not the parent node? Or there
should be a reg property for child node to tell register offset etc?

There are way too much usage that children "depends" on parents somehow
in tree, so I want to confirm my understanding.

For boston-platform-regs there are some other PHYs that I may add drivers
for them in future, so I certainly want "simple-mfd" to be here 


-- 
- Jiaxun