Quoting Pavan Kondeti (2022-06-27 22:31:48) > On Mon, Jun 27, 2022 at 01:02:49PM -0700, Stephen Boyd wrote: > > Quoting Pavan Kondeti (2022-06-20 01:54:15) > > > > > > Would like to hear other people thoughts on this. > > > > > > > I'm not following very closely but it sounds like a problem that may be > > solved by using the component driver code (see > > include/linux/component.h). That would let you move anything that needs > > to be done once the child devices probe to the aggregate driver 'bind' > > function (see struct component_master_ops::bind). > > Thanks Stephen for letting us know about the component device framework. > > IIUC, > > - dwc3-qcom (parent of the dwc3 core) registers as a component master by > calling component_master_add_with_match() before calling > of_platform_populate(). The match callback could be as simple as comparing > the device against our child device. > > - The dwc3 core (child) at the end of its probe can add as a component by calling > component_add(). > > - The above triggers the component_master_ops::bind callback implemented in > dwc3-qcom driver which signals that we are good to go. > > - The dwc-qcom can call component_bind_all() to finish the formality i.e > telling the dwc3 core that we are good to go. > > Is my understanding correct? This is what we are looking for i.e a way for > the child device(s) to signal the parent when the former is bounded. Sounds about right to me. > > Also what happens when the child device probe fails for any reason. i.e > component_add() would never be called so the master driver i.e dwc3-qcom would > wait indefinitely. May be it needs to implement a timeout or runtime suspend > etc should take care of keeping the resoures in suspend state. When the child fails probe, it should return -EPROBE_DEFER if probe needs to be deferred. Then the driver will attempt probe at a later time. If probe fails without defer then it will never work and dwc3-qcom will wait indefinitely. Not much we can do in that situation. dwc3-qcom should wait for dwc3 core to call component_add() and then do whatever needs to be done once the dwc3 core is registered in the dwc3-qcom bind callback. Honestly this may all be a little overkill if there's only two drivers here, dwc3-qcom and dwc3 core. It could probably just be some callback from dwc3 core at the end of probe that calls some function in dwc3-qcom.
