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
BR // Mats
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