linux-kernel - Re: [RESEND PATCH 2/2] usb: dwc3: pci add property to allow user space role switch

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Date:   Wed, 25 Aug 2021 10:43:38 +0300
From:   Felipe Balbi <balbi@...nel.org>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Nehal Bakulchandra Shah <Nehal-Bakulchandra.shah@....com>,
        gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, kun.liu2@....com,
        alexander.deucher@....com
Subject: Re: [RESEND PATCH 2/2] usb: dwc3: pci add property to allow user
 space role switch


Heikki Krogerus <heikki.krogerus@...ux.intel.com> writes:

> On Wed, Aug 25, 2021 at 08:55:41AM +0300, Felipe Balbi wrote:
>> 
>> Hi,
>> 
>> Nehal Bakulchandra Shah <Nehal-Bakulchandra.shah@....com> writes:
>> 
>> > For AMD platform there is a requirement to enable user space role
>> > switch from host to device and device to host as customer platform is not
>> > completely capable of OTG i.e. with type C controller it does not have PD
>> > to support role switching. Hence, based ACPI/EC interrupt role switch is
>> > triggered by the usemode script running in background.
>>                    usermode ?
>
> Couldn't you capture that ACPI/EC interrupt in kernel?
>
>> > Signed-off-by: Nehal Bakulchandra Shah <Nehal-Bakulchandra.shah@....com>
>> 
>> I'm okay with this, just wondering if we need to Document the property
>> somewhere.
>> 
>> @Heikki, is there a place to document these private properties that's
>> not on DT binding document?
>
> The build-in properties are not documented separately. I've always
> tried to supply DT bindings for all new properties I've proposed.
>
> In this case though, do we need the new property at all? Why not just
> register a normal USB role switch on this platform? It can be either a
> dummy role switch that only passes the user space input to dwc3, or,
> perhaps ideally, it would also be a driver that captures that ACPI/EC
> event/notification and then passes the information from it to dwc3.

I like the actual driver responding to EC IRQ idea.

-- 
balbi