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

From: Guenter Roeck <linux@roeck-us.net>
To: Mats Karrman <mats.dev.list@gmail.com>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Greg KH <gregkh@linuxfoundation.org>
Cc: Felipe Balbi <felipe.balbi@linux.intel.com>,
	Oliver Neukum <oneukum@suse.com>,
	linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org
Subject: Re: [PATCH v17 2/3] usb: USB Type-C connector class
Date: Fri, 3 Mar 2017 06:41:40 -0800	[thread overview]
Message-ID: <56a9ca99-b43c-3a6c-dc66-ed4887e5a5cd@roeck-us.net> (raw)
In-Reply-To: <07618170-d561-e7fe-08e0-91316c53d832@gmail.com>

On 03/02/2017 11:29 PM, Mats Karrman wrote:
> 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.
>
> 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.
>

Sounds quite similar to rk3399 (Samsung Chromebook Plus). I have not ported the Type-C class code
to that system yet, but it does use the extcon cros_ec driver, and DP connectivity is signaled
to the DP code through extcon events.

> 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?
>
See above. The code is available in the repository mentioned above.

Guenter

> 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
>
>