Hi Cristian, On Mon, Feb 15, 2021 at 05:25:29PM +0000, Cristian.Birsan@xxxxxxxxxxxxx wrote: > My name is Cristian and I'm working on bringing up a USB Type-C Port Controller > (TCPC) without Power Delivery support which is intended to work with USB 2.0 > Host/Device. > > The IP is integrated into one of Microchip's SoCs, it is memory-mapped and it > was designed based on USB Type-C Cable and Connector specification revision 1.2. > > In brief, it has support for detecting the threshold voltages on CC1, CC2 lines, > control of the current source (Ip), and pull-down resistors (Rd). The management > of the controller is to be implemented in software (it is not autonomous). > > Having in mind that the controller uses proprietary registers, I chose to > implement it using TCPM directly and skip the TCPC Interface. > > For the beginning, I would like to enable simple use cases like the ones > described in Connection State Diagram: Source and Connection State Diagram: Sink > from USB Type-C Cable and Connector Specification. > > Some of the problems that I encountered until now are: > > 1. tcpm_register_port() fails if set_pd_rx(), pd_transmit() or set_vconn() > functions are missing. > > 2. the port capabilities are specified in the connector DT bindings only through > PDOs, even though PDOs are specific to PD mode. > > 3. once I was able to start the TCPM state machine, it called pd_transmit() in > the process to negotiate the capabilities. For my case I used a dummy function > just to be able to register the port. > > Please let me know what you think and if you have any advice. Am I going in the > right direction or is there a better way to implement this? Don't bother with tcpm if you don't have PD support. Just register your port(s) and the partners directly with the connector class: https://www.kernel.org/doc/html/latest/driver-api/usb/typec.html You can use the driver for the TI HD3SS3220 controller as an example how to do that (drivers/usb/typec/hd3ss3220.c). That thing is also just USB Type-C PHY without PD support just like your port controller. Br, -- heikki
