linux-kernel - Re: [PATCH v9 0/4] Introduce usb charger framework to deal with the usb gadget power negotation

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Message-ID: <20160405064637.GA31351@shlinux2.ap.freescale.net>
Date:	Tue, 5 Apr 2016 14:46:37 +0800
From:	Peter Chen <hzpeterchen@...il.com>
To:	Baolin Wang <baolin.wang@...aro.org>
Cc:	balbi@...nel.org, gregkh@...uxfoundation.org, sre@...nel.org,
	dbaryshkov@...il.com, dwmw2@...radead.org,
	peter.chen@...escale.com, stern@...land.harvard.edu,
	r.baldyga@...sung.com, yoshihiro.shimoda.uh@...esas.com,
	lee.jones@...aro.org, broonie@...nel.org,
	ckeepax@...nsource.wolfsonmicro.com,
	patches@...nsource.wolfsonmicro.com, linux-pm@...r.kernel.org,
	linux-usb@...r.kernel.org,
	device-mainlining@...ts.linuxfoundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 0/4] Introduce usb charger framework to deal with the
 usb gadget power negotation

On Fri, Apr 01, 2016 at 03:21:48PM +0800, Baolin Wang wrote:
> Currently the Linux kernel does not provide any standard integration of this
> feature that integrates the USB subsystem with the system power regulation
> provided by PMICs meaning that either vendors must add this in their kernels
> or USB gadget devices based on Linux (such as mobile phones) may not behave
> as they should. Thus provide a standard framework for doing this in kernel.
> 
> Now introduce one user with wm831x_power to support and test the usb charger,
> which is pending testing. Moreover there may be other potential users will use
> it in future.
> 
> Changes since v8:
>  - Remove the bus type things.
>  - Introduce one charger_detect() callback to detect charger type if it is needed.
>  - Add some sysfs attributes for showing the charger type and state.
>  - Change the charger current attributes to read only.
>  - Move charger state and type definition to include/uapi.
>  - Some other optimiazations.
> 
> Baolin Wang (4):
>   gadget: Introduce the usb charger framework
>   gadget: Support for the usb charger framework
>   gadget: Integrate with the usb gadget supporting for usb charger
>   power: wm831x_power: Support USB charger current limit management
> 

We are thinking USB charger framework for Freescale i.mx SoC series,
since our internal framework is not good enough.
So I have more questions for your framework since there are many
different USB charger designs, and I hope it is universal.

- I would like to see your all code to let the charger work, eg
you have said the charger detection is done by PMIC automatically,
but I did not find your PMIC code to read charger type.

Besides, how you can make sure the charger detection has finished
before the framework handles USB_CHARGER_PRESENT event?

- I commented the current limit at different situations for USB
charger last time, but I have not seen your further comments.
I would like give it again. For DCP, you can notify charger IC
once you get the charger type. But for CDP/SDP, you need to
notify charger IC after set configuration has finished, since
the host may still not be ready to give high current.

-- 

Best Regards,
Peter Chen