RE: [PATCH v19 0/4] Introduce usb charger framework to deal with the usb gadget power negotation

[Jun Li <jun.li@nxp.com>]

Hi

> -----Original Message-----
> From: Baolin Wang [mailto:baolin.wang@linaro.org]
> Sent: Friday, March 10, 2017 3:15 PM
> To: Jun Li <jun.li@nxp.com>
> Cc: NeilBrown <neilb@suse.com>; Felipe Balbi <balbi@kernel.org>; Greg KH
> <gregkh@linuxfoundation.org>; Sebastian Reichel <sre@kernel.org>; Dmitry
> Eremin-Solenikov <dbaryshkov@gmail.com>; David Woodhouse
> <dwmw2@infradead.org>; robh@kernel.org; Marek Szyprowski
> <m.szyprowski@samsung.com>; Ruslan Bilovol <ruslan.bilovol@gmail.com>;
> Peter Chen <peter.chen@freescale.com>; Alan Stern
> <stern@rowland.harvard.edu>; grygorii.strashko@ti.com; Yoshihiro Shimoda
> <yoshihiro.shimoda.uh@renesas.com>; Lee Jones <lee.jones@linaro.org>;
> Mark Brown <broonie@kernel.org>; John Stultz <john.stultz@linaro.org>;
> Charles Keepax <ckeepax@opensource.wolfsonmicro.com>;
> patches@opensource.wolfsonmicro.com; Linux PM list <linux-
> pm@vger.kernel.org>; USB <linux-usb@vger.kernel.org>; device-
> mainlining@lists.linuxfoundation.org; LKML <linux-kernel@vger.kernel.org>
> Subject: Re: [PATCH v19 0/4] Introduce usb charger framework to deal with
> the usb gadget power negotation
> 
> On 10 March 2017 at 14:30, Jun Li <jun.li@nxp.com> wrote:
> >> >> >
> >> >> > Will generic phy need add extcon as well?
> >> >>
> >> >> Yes, will add a 'struct extcon_dev*' in 'struct usb_phy', which
> >> >> will be common code.
> >> >>
> >> >
> >> > I mean the common code need add 'struct extcon_dev' into both
> >> > 'struct phy' and 'struct usb_phy', right? as some/new usb phy use
> >> > that generic phy
> >> driver.
> >>
> >> Ah, you remind me. Seems we need also add one 'struct extcon_dev'
> >> into 'struct phy'.
> >>
> >> >> >
> >> >> >> >
> >> >> >> >> Secondly, I also agreed with Peter's comments: Not only USB
> >> >> >> >> PHY to register an extcon, but also for the drivers which
> >> >> >> >> can detect USB charger type, it may be USB controller
> >> >> >> >> driver, USB type-c driver, pmic driver, and these drivers
> >> >> >> >> may not have an extcon device since the internal part can finish
> the vbus detect.
> >> >> >> >
> >> >> >> > Whichever part can detect vbus, the driver for that part must
> >> >> >> > be able to find the extcon and trigger a notification.
> >> >> >> > Maybe one part can detect VBUS, another can measure the
> >> >> >> > resistance on ID and a third can work through the state
> >> >> >> > machine to determine if D+ and D- are shorted together.
> >> >> >> > Somehow these three need to work together to determine what
> >> >> >> > is
> >> >> >> plugged
> >> >> >> > in to the external connection port.  Somewhere there much an
> >> 'extcon'
> >> >> >> > device which represents that port and which the three devices
> >> >> >> > can find and can interact with.
> >> >> >> > I think it makes sense for the usb_phy to be the connection point.
> >> >> >> > Each of the devices can get to the phy, and the phy can get
> >> >> >> > to the
> >> >> extcon.
> >> >> >> > It doesn't matter very much if the usb phy driver creates the
> >> >> >> > extcon, or if something else creates the extcon and the phy
> >> >> >> > driver performs a lookup to find it (e.g. based on devicetree info).
> >> >> >> >
> >> >> >> > The point is that there is obviously an external physical
> >> >> >> > connection, and so there should be an 'extcon' device that
> >> represents it.
> >> >> >>
> >> >> >> Peter & Jun, is it OK for you every phy has one extcon device
> >> >> >> to receive VBUS notification, especially for detecting the
> >> >> >> charger type by
> >> >> software?
> >> >> >>
> >> >> >
> >> >> > My understanding is phy/usb_phy as the connection point, will
> >> >> > send the notification to PMIC driver which actually control the
> >> >> > charge current, also this will be done in your common framework,
> right?
> >> >>
> >> >> Not in USB charger framework. If we are all agree every usb_phy
> >> >> can register one extcon device, can get correct charger type and
> >> >> send out correct vbus_draw information, then we don't need USB
> >> >> charger framework as Neil suggested. So this will be okay for your
> >> >> case (especially for detecting the charger type by software) ?
> >> >
> >> > In my case, charger detection is done by controller driver and I
> >> > need do charger type detection internally, and only pass the
> >> > current draw info via phy which will send out, this seems ok for
> >> > me, but I think it will be good if you or someone can show us an
> >> > example user based on the
> >> design Neil suggested.
> >> > Will you work out that common code if this USB charger framework is
> >> > not
> >> needed?
> >>
> >> I will add  a 'struct extcon_dev*' in 'struct usb_phy' and struct
> >> phy“. Others are already ready if everyone has no complain about
> >> current design, except
> >
> > Only adding extcon_dev into usb_phy/phy  and all others are ready?
> > My understanding you will also do:
> > - We need find a central place to send the notification(phy common part).
> 
> That will include these implementation when adding extcon_dev.
> 

OK, thanks.

> > - If the extcon_dev is directly added in usb_phy/phy, PMIC needs some
> API to findup it.
> 
> PMIC can find extcon device by phandle.

extcon_dev(not a reference pointer) is directly added in usb_phy/phy, not via devicetree,
how PMIC find it by phandle?
 
> 
> >
> >> my one concern. (I am afraid if it is enough to send out vbus draw
> >> information from USB phy driver, for example you will miss super
> >> speed (900mA), which need get the speed information from gadget
> >> driver.)
> >>
> >
> > Can we handle this in USB(so has super speed information) and just
> > send out 900mA directly?
> 
> From Neil's suggestion, we only have one place to send out current
> information from usb phy, so I have this concern and doubt if we still need
> the USB charger framework.

So if put it in phy/usb_phy, this is a problem, that only one place should have
the infor of both speed and usb state, how about put it at usb_gadget, then,
e.g. send the notification in usb_gadget_vbus_connect()?

Li Jun

> 
> --
> Baolin.wang
> Best Regards