On 31 March 2016 at 14:18, Felipe Balbi <balbi@xxxxxxxxxx> wrote: > > Hi, > > Baolin Wang <baolin.wang@xxxxxxxxxx> writes: >> [ text/plain ] >> 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()'. > > 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. Make sense. > > -- > 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
