On Thu 08 Jul 03:17 PDT 2021, Bryan O'Donoghue wrote: > On 08/07/2021 04:54, Bjorn Andersson wrote: > > Bryan had a previous patch where the glue layer was notified about role > > switching (iirc) and as soon as we hit a probe deferal in the core > > driver we'd dereference some pointer in the glue layer. I don't find the > > patch right now, but I suspect it might have been caused by the same > > platform_get_drvdata() as we see in qcom_dwc3_resume_irq(). > > Here > > https://lore.kernel.org/linux-usb/20200311191501.8165-7-bryan.odonoghue@xxxxxxxxxx/ > > and here > > https://lore.kernel.org/linux-usb/20200311191501.8165-8-bryan.odonoghue@xxxxxxxxxx/ > Now that I dug through the code I remembered why this didn't work. You do: dwc = platform_get_drvdata(qcom->dwc3); In order to be able to register the callback in the notifier chain that you added to struct dwc3, but while qcom->dwc3 is a valid struct platform_device, it might not have probed yet and "dwc" becomes NULL, which you then dereferenced in dwc3_role_switch_notifier_register(). So we need a mechanism that passes that callback/notifier that has a life cycle matching that of the glue device. > one thing about that I don't think is right now in retrospect is having to > find a DT connector in the core, meaning it incorrectly assumes you have a > node named "connector" as a child of dwc3-core > > https://lore.kernel.org/linux-usb/158463604559.152100.9219030962819234620@xxxxxxxxxxxxxxxxxxxxxxxxxx/ > > Having done some work with TCPM on pm8150b silicon I see what Stephen was > saying about that > > That's one solid reason I like the USB role-switch API - because it gets you > out of the business of trying to discern from dwc3-qcom if dwc3-core has > role-switching turned on by iterating through its range of DT nodes and > looking for a special one named "connector" > > The initial and imperfect solution I had for that looked like this > > if (dwc3_qcom_find_gpio_usb_connector(qcom->dwc3)) {} > > Wesley had another iteration on that that was a little better > > https://lore.kernel.org/linux-usb/20201009082843.28503-4-wcheng@xxxxxxxxxxxxxx/ > > +static int dwc3_qcom_connector_check(struct fwnode_handle *fwnode) > +{ > + if (fwnode && (!fwnode_property_match_string(fwnode, "compatible", > + "gpio-usb-b-connector") || > + !fwnode_property_match_string(fwnode, "compatible", > + "usb-c-connector"))) > + return 1; > + > + return 0; > +} > > All we are really doing there is replicating functionality that the > role-switch API already provides > But isn't this role switching interaction (both B and C) already part of the core/drd, so if we can just get the drd to invoke dwc3_qcom_vbus_overrride_enable() we're done (and can remove all the extcon code from the qcom glue as well)? Regards, Bjorn
