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

[Guenter Roeck]

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