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

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Date:	Wed, 30 Mar 2016 17:32:16 +0800
From:	Baolin Wang <baolin.wang@...aro.org>
To:	Peter Chen <hzpeterchen@...il.com>
Cc:	Mark Brown <broonie@...nel.org>, 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>,
	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 17:19, Peter Chen <hzpeterchen@...il.com> wrote:
> On Wed, Mar 30, 2016 at 04:40:31PM +0800, Baolin Wang wrote:
>> >> > - Third, since composite driver covers 500mA (and more for CDP) after set
>> >> > configuration and 2mA after suspend, and vbus handler covers connect
>> >> > and disconnect. I can't see any reasons we need to notify gadget state
>> >> > for power driver, do we really need to have usb_charger_plug_by_gadget?
>> >>
>> >> In some solutions, gadget does not negotiate with the current. They
>> >> just send out one signal to power driver to set the current when the
>> >> gadget state is changed (plugin or not). So we need to check the
>> >> charger state by the gadget state to notify the charger IC to set
>> >> current.
>> >>
>> >
>> > Would you give some examples?
>>
>> OK. I explain it in detail. Now charger detection can be from gadget
>> itself or PMIC, and we focus on gadget detection. Charger IC (charger
>> driver) is separate with gadget.
>> When the usb cable is plugin, we need to report the plugin event to
>> charger driver to set current after setting configuration for gadget.
>> The usb charger is responsible for reporting plugin event to charger
>> driver. But how usb charger get the plugin event? It can get the
>> plugin event from gadget state (if the gadget state is more than
>> 'USB_STATE_ATTACHED', it means one cable plugin). So we need notify
>> gadget state to usb charger.
>>
>
> Ok, I see, it only changes current limit at function usb_gadget_vbus_draw
> in your patch 2/4. Then, we need to make sure usb_charger_set_cur_limit_by_type
> is called before calling usb_gadget_set_state(gadget, USB_STATE_CONFIGURED).

That's right.

>
> It seems you have not implemented usb_charger_plug_by_gadget in your patch set.

It is implemented in patch 3/4.

>
> --
> Best Regards,
> Peter Chen



-- 
Baolin.wang
Best Regards