On 31 March 2016 at 14:12, Jun Li <jun.li@xxxxxxx> wrote: > Hi > >> -----Original Message----- >> From: Baolin Wang [mailto:baolin.wang@xxxxxxxxxx] >> Sent: Thursday, March 31, 2016 1:23 PM >> To: Jun Li <jun.li@xxxxxxx> >> Cc: Peter Chen <hzpeterchen@xxxxxxxxx>; Felipe Balbi <balbi@xxxxxxxxxx>; >> Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>; Sebastian Reichel <sre@xxxxxxxxxx>; >> Dmitry Eremin-Solenikov <dbaryshkov@xxxxxxxxx>; David Woodhouse >> <dwmw2@xxxxxxxxxxxxx>; Peter Chen <peter.chen@xxxxxxxxxxxxx>; Alan Stern >> <stern@xxxxxxxxxxxxxxxxxxx>; r.baldyga@xxxxxxxxxxx; Yoshihiro Shimoda >> <yoshihiro.shimoda.uh@xxxxxxxxxxx>; Lee Jones <lee.jones@xxxxxxxxxx>; Mark >> Brown <broonie@xxxxxxxxxx>; Charles Keepax >> <ckeepax@xxxxxxxxxxxxxxxxxxxxxxxxxxx>; patches@xxxxxxxxxxxxxxxxxxxxxxxxxxx; >> Linux PM list <linux-pm@xxxxxxxxxxxxxxx>; USB <linux-usb@xxxxxxxxxxxxxxx>; >> device-mainlining@xxxxxxxxxxxxxxxxxxxxxxxxx; LKML <linux- >> kernel@xxxxxxxxxxxxxxx> >> Subject: Re: [PATCH v8 0/4] Introduce usb charger framework to deal with >> the usb gadget power negotation >> >> On 30 March 2016 at 18:58, Jun Li <jun.li@xxxxxxx> 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 >> > before SW do gadget connect. To make the framework common, you may do >> one time charger type check when vbus is on, and save it to avoid repeat >> charger type check. >> >> OK. I'll add one judgement to check if the charger type is set in >> 'usb_charger_detect_type()' function. > > Just adding a judgement isn't enough here, your framework should make sure > usb_charger_detect_type() is called before gadget connect, with that, the > existing caller place just gets the charger type from the saved value. > The real charger type detection done by usb_charger_detect_type() can > be called only when vbus is on. > e.g. maybe in usb_udc_vbus_handler() before usb_udc_connect_control(). Yeah, Like Felipe suggested, I think we need to introduce one 'charger_detect()' method to do the SW charger type detection at the right gadget state. Thanks for your comments. >> >> -- >> Baolin.wang >> Best Regards -- 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
