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 17:19:50 +0800
From:	Peter Chen <hzpeterchen@...il.com>
To:	Baolin Wang <baolin.wang@...aro.org>
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 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).

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

-- 
Best Regards,
Peter Chen