linux-kernel - Re: [PATCH 0/3] extcon: Add Type-C Virtual PD

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Date:   Tue, 15 Sep 2020 10:17:39 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Rob Herring <robh@...nel.org>,
        Heiko Stübner <heiko@...ech.de>,
        Jagan Teki <jagan@...rulasolutions.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>, Tom Cubie <tom@...xa.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-amarula@...rulasolutions.com
Subject: Re: [PATCH 0/3] extcon: Add Type-C Virtual PD

Hi Rob,

On 9/15/20 8:15 AM, Rob Herring wrote:
> On Fri, Sep 04, 2020 at 11:23:21PM +0200, Heiko Stübner wrote:
>> Hi Jagan,
>>
>> Am Freitag, 4. September 2020, 21:18:27 CEST schrieb Jagan Teki:
>>> USB Type-C protocol supports various modes of operations
>>> includes PD, USB3, and Altmode. If the platform design
>>> supports a Type-C connector then configuring these modes
>>> can be done via enumeration.
>>>
>>> However, there are some platforms that design these modes
>>> of operations as separate protocol connectors like design
>>> Display Port from on-chip USB3 controller. So accessing
>>> Type-C Altmode Display Port via onboard Display Port 
>>> connector instead of a Type-C connector.
>>>  
>>> These kinds of platforms require an explicit extcon driver
>>> in order to handle Power Delivery and Port Detection.
>>>
>>> This series support this Type-C Virtual PD and enable the
>>> same in ROCK Pi 4C SBC.
>>>
>>> Any inputs?
>>
>> I tend to disagree on the design via an extcon.
> 
> I don't accept new extcon bindings or users of it either. It's a 
> poorly thought out collection of Linux driver properties. Use the usb 
> connector binding.

I agree the prior binding format of extcon with 'extcon' property name
is not proper. So, I'll try to bind new style. But, I have a question.
Do you have the objection of the use of extcon like 'users of it either' 
of your comment?

> 
>>
>> That the Rockchip rk3399 currently carries that extcon thingy is unfortunate
>> and only works for ChromeOS devices based on the rk3399.
>>
>> The kernel now has a real type-c framework so we should not extend this
>> extcon hack any further, because that will make it even harder to roll back
>> later. Also simply because other Rockchip boards currently can't really make
>> use of type-c due to this, as they use the fsusb302 phys directly connected.
>>
>> ChromeOS actually spend some time to make the cros-ec pd part of the type-c
>> framework if I remember correctly, so a viable battle plan would be to:
>>
>> (1) move the Rockchip type-c phy driver to actually be part of the type-c
>>     framework, with the extcon being a deprecated fallback for old DTs.
>> (2) implement your gpio-altmode as part of the type-c framework
>>     (which may even already exist)
>>
>>
>> In short, please don't extend the rk3399 type-c extcon hack.
>>
>> Thanks
>> Heiko
>>
>>
>>
>>
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics