linux-kernel - RE: [PATCH v8 0/4] Introduce usb charger framework to deal with the usb gadget power negotation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 30 Mar 2016 14:24:41 +0300
From:	Felipe Balbi <balbi@...nel.org>
To:	Jun Li <jun.li@....com>, Baolin Wang <baolin.wang@...aro.org>
Cc:	Peter Chen <hzpeterchen@...il.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Peter Chen <peter.chen@...escale.com>,
	Alan Stern <stern@...land.harvard.edu>,
	"r.baldyga\@samsung.com" <r.baldyga@...sung.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	Lee Jones <lee.jones@...aro.org>,
	Mark Brown <broonie@...nel.org>,
	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>,
	"patches\@opensource.wolfsonmicro.com" 
	<patches@...nsource.wolfsonmicro.com>,
	Linux PM list <linux-pm@...r.kernel.org>,
	USB <linux-usb@...r.kernel.org>,
	"device-mainlining\@lists.linuxfoundation.org" 
	<device-mainlining@...ts.linuxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v8 0/4] Introduce usb charger framework to deal with the usb gadget power negotation


Hi,

Jun Li <jun.li@....com> writes:
>> -----Original Message-----
>> From: Baolin Wang [mailto:baolin.wang@...aro.org]
>> Sent: Wednesday, March 30, 2016 5:31 PM
>> To: Jun Li <jun.li@....com>
>> Cc: Peter Chen <hzpeterchen@...il.com>; Felipe Balbi <balbi@...nel.org>;
>> Greg KH <gregkh@...uxfoundation.org>; Sebastian Reichel <sre@...nel.org>;
>> Dmitry Eremin-Solenikov <dbaryshkov@...il.com>; David Woodhouse
>> <dwmw2@...radead.org>; Peter Chen <peter.chen@...escale.com>; Alan Stern
>> <stern@...land.harvard.edu>; r.baldyga@...sung.com; Yoshihiro Shimoda
>> <yoshihiro.shimoda.uh@...esas.com>; Lee Jones <lee.jones@...aro.org>; Mark
>> Brown <broonie@...nel.org>; Charles Keepax
>> <ckeepax@...nsource.wolfsonmicro.com>; patches@...nsource.wolfsonmicro.com;
>> Linux PM list <linux-pm@...r.kernel.org>; USB <linux-usb@...r.kernel.org>;
>> device-mainlining@...ts.linuxfoundation.org; LKML <linux-
>> kernel@...r.kernel.org>
>> Subject: Re: [PATCH v8 0/4] Introduce usb charger framework to deal with
>> the usb gadget power negotation
>> 
>> On 30 March 2016 at 16:07, Jun Li <jun.li@....com> wrote:
>> > Hi
>> 
>> >> On 30 March 2016 at 10:54, Jun Li <jun.li@....com> wrote:
>> >> >> >> It is not for udc driver but for power users who want to
>> >> >> >> negotiate with USB subsystem.
>> >> >> >>
>> >> >> >
>> >> >> > 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.

-- 
balbi

Download attachment "signature.asc" of type "application/pgp-signature" (819 bytes)