Hi, Baolin Wang <baolin.w...@linaro.org> writes: > [ text/plain ] > On 30 March 2016 at 19:24, Felipe Balbi <ba...@kernel.org> 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()'.
yes. > 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. they shouldn't detect is get_type(), the semantics doesn't work. If, at some point, we have to do SW detection of the charger, then a new ->charger_detect() method will have to be added. -- balbi
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