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

[Baolin Wang]

On 10 March 2017 at 14:30, Jun Li <jun.li@xxxxxxx> 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 phyâ. 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.

> - 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.

>
>> 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.

-- 
Baolin.wang
Best Regards