linux-kernel - Re: [PATCH v17 2/3] usb: USB Type-C connector class

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Date:   Fri, 3 Mar 2017 10:48:22 +0100
From:   Enric Balletbo Serra <eballetbo@...il.com>
To:     Mats Karrman <mats.dev.list@...il.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Oliver Neukum <oneukum@...e.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH v17 2/3] usb: USB Type-C connector class

2017-03-03 8:29 GMT+01:00 Mats Karrman <mats.dev.list@...il.com>:
> On 2017-03-03 04:13, Guenter Roeck wrote:
>
>> On 03/02/2017 07:22 AM, Mats Karrman wrote:
>>>
>>> ....
>>> Looking forward, one thing I have run into is how to connect the typec
>>> driver with a
>>> driver for an alternate mode. E.g. the DisplayPort Alternate Mode
>>> specification
>>> includes the HPD (hot plug) and HPD-INT (hot plug interrupt) signals as
>>> bits in the
>>> Attention message. These signals are needed by the DisplayPort driver to
>>> know when to
>>> start negotiation etc.
>>> Have you got any thoughts on how to standardize such interfaces?
>>
>> That really depends on the lower level driver. For Chromebooks, where the
>> Type-C
>> Protocol Manager runs on the EC, we have an extcon driver which reports
>> the pin states
>> to the graphics drivers and connects to the Type-C class code using the
>> Type-C class
>> API. I still need to update, re-test, and publish that code. The published
>> code in
>> https://chromium.googlesource.com/chromiumos/third_party/kernel/, branch
>> chromeos-4.4,
>> shows how it can be done, though that code currently still uses the
>> Android Type-C
>> infrastructure.
>

On a side note, the cros-ec extcon part for DP is currently discussed
here [1]. This driver works together with the cdn-dp driver that just
landed in mainline. So comments and feedback are welcome

[1] https://lkml.org/lkml/2017/3/1/301

>
> OK, thanks!
>
> My system is a bit different. It's an i.MX6 SoC with the typec phy and DP
> controller connected
>
> directly to the SoC and it's using DTB/OF.
>
> Using extcon I would have a driver that is both typec class and extcon
> driver at the same time
>
> since I can't share the access to the typec phy. Is this done elsewhere in
> the kernel?
>
> I don't know much about the wcove PMIC and what alternate modes it might
> support but I
>
> guess that driver would end up in the same place.
>
> Do we need to further standardize attributes under (each) specific alternate
> mode to
>
> include things such as HPD for the DP mode?
>
> BR // Mats
>