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

[Guenter Roeck]

On 03/10/2017 02:22 PM, Mats Karrman wrote:
> On 2017-03-08 14:58, Heikki Krogerus wrote:
>
> > On Tue, Mar 07, 2017 at 11:30:54PM +0100, Mats Karrman wrote:
> > > If I read Heikki's original suggestion I understand it like the DP driver would be
> > > responsible for AM specific USB PD/VDM communication. But wouldn't that lead
> > > to a lot of code duplication since the AM protocol is the same for all drivers of
> > > a kind?
> > No that's not what I mean. I'm still mixing your PD controller with
> > something else above, sorry about that. Your PD controller driver
> > should not ideally even need to be aware of Type-C connector, right?
> > It definitely does not need to do any USB PD communication.
>
> Right.
>
> > I would imagine you have on top of the DP controller, a mux (which
> > could be a DP/USB3 PHY like on Rockchip RK3399, discrete mux like
> > Pericom PI3USB30532, or something else), and a USB Type-C PHY or USB
> > PD controller. The bus would be tying the mux to the Type-C port (PHY
> > or PD controller) and its partner (note that it does not tie the mux
> > to the DP controller). Please correct me if I'm wrong about your
> > hardware.
>
> No, you're correct, a discrete mux and a fusb302.
>
> > Assuming that is how your board roughly looks like, the driver for the
> > mux would be the driver for the DP altmode devices. That driver would
> > be the one converting things like the Attention messages notifying
> > about HPD into toggling of GPIOs, or what ever is needed on your
> > board, etc.
>
> OK.
>
> > The actual PD communication with VDMs should be considered as just the
> > protocol, so we probable should have "protocol drivers". For example
> > DP alternate mode VDMs and communication will always be the same
> > despite of the hardware. The DP alternate mode "protocol driver" would
> > then be tied to the alternate mode device for the partner, and that
> > driver could have its own hooks for what ever is needed, like HPD
> > signal handling, configuration changes, whatever. In any case,
> > hopefully making things easy and straightforward for the "mux driver",
> > _so that it does not need to care about the actual PD communication_.
>
> I'm digesting your and Guenter's replies and patches.
> I will try getting something up and running too soon and hopefully the foggy parts will
> dissolve. As for now I find it a lot easier to grok Guenter's drivers than to see the
> advantages and/or disadvantages of an altmode bus :-)
>
> @Guenter: There _is_ interest for your fusb302 driver, thank you

Ok, I'll see what I need to do to publish it.

Guenter