On 30 March 2016 at 19:24, Felipe Balbi <balbi@xxxxxxxxxx> wrote: >>> >> >> > >>> >> >> > Seems you don't want to guarantee charger type detection is done >>> >> >> > before gadget connection(pullup DP), right? >>> >> >> > I see you call usb_charger_detect_type() in each gadget usb >>> >> >> > state >>> >> >> changes. >>> >> >> >>> >> >> I am not sure I get your point correctly, please correct me if I >>> >> >> misunderstand you. >>> >> >> We need to check the charger type at every event comes from the >>> >> >> usb gadget state changes or the extcon device state changes, which >>> >> >> means a new charger plugin or pullup. >>> >> >> >>> >> > >>> >> > According to usb charger spec, my understanding is you can't do >>> >> > real charger detection procedure *after* gadget _connection_(pullup >>> >> > DP), also I don't >>> >> >>> >> Why can not? Charger detection is usually from PMIC. >>> > >>> > Charger detection process will impact DP/DM line state, see usb >>> > charger spec v1.2 for detail detection process, section 4.6.3 says: >>> > >>> > "A PD is allowed to *disconnect* and repeat the charger detection >>> > process multiple times while attached. The PD is required to wait for >>> > a time of at least TCP_VDM_EN max between disconnecting and restarting >>> > the charger detection process." >>> > >>> > As Peter mentioned, the charger detection should happen between VBUS >>> > detection and gadget pull up DP for first plug in case. So when&after >>> > gadget connect (pullup DP), you should already know the charger type. >>> >>> Make sense. In our company's solution, charger detection can be done by >>> hardware from PMIC at first, then it will not affect the DP/DM line when >>> gadget starts to enumeration. >> >> I see, charger type detection is done automatically by PMIC when VBUS >> is detected in your case, you just assume the process is complete > > assuming this finishes before gadget starts is a bad idea. It would've > been much more robust to delay usb_gadget_connect() until we KNOW > charger detection has completed. It is hardware action to detect the charger type quickly. It actually *gets* the charger type and does not means *detect* charger type in 'usb_charger_detect_type()' function. Maybe I need to change the function name as 'usb_charger_get_type()'. If some udc drivers want to detect charger type in 'gadget->ops->get_charger_type()' callback, they should avoid impacting DP/DM line state at the right gadget state. Thanks. > > -- > balbi -- Baolin.wang Best Regards -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
