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

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Message-ID: <CAMz4ku+PAn3nUGg7gs04cPHhn16cKgNv_+duv-kz0GqOEYTYkQ@mail.gmail.com>
Date:   Thu, 30 Mar 2017 11:16:59 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     NeilBrown <neilb@...e.com>
Cc:     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>, robh@...nel.org,
        Jun Li <jun.li@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Ruslan Bilovol <ruslan.bilovol@...il.com>,
        Peter Chen <peter.chen@...escale.com>,
        Alan Stern <stern@...land.harvard.edu>,
        grygorii.strashko@...com,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Mark Brown <broonie@...nel.org>,
        John Stultz <john.stultz@...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 v19 0/4] Introduce usb charger framework to deal with the
 usb gadget power negotation

Hi,

On 29 March 2017 at 07:04, NeilBrown <neilb@...e.com> wrote:
> On Tue, Mar 07 2017, Baolin Wang wrote:
>
>> On 3 March 2017 at 10:23, NeilBrown <neilb@...e.com> wrote:
>>
>>>
>>> I understand your reluctance to change drivers that you cannot test.
>>> An alternative it do change all the
>>>   atomic_notifier_call_chain(.*notifier,
>>> calls that don't pass a pointer to vbus_draw to pass NULL, and to
>>> declare the passing of NULL to be deprecated (so hopefully people won't
>>> use it in new code).
>>> Then any notification callback that expects a current can just ignore
>>> calls where the pointer is NULL.
>>
>> 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.
>
> When the gadget driver determines that 900mA is available, it calls
> usb_phy_set_power() which calls the ->set_power() method on the usb_phy.
> The usb_phy the uses the notifier to inform all interested parties
> that 900mA is available.

That is one possible way. Now we only set vbus draw by
usb_gadget_vbus_draw() after setting config and suspend/resume usb
device. Maybe we can add one condition in usb_gadget_vbus_draw() like:

if (mA >= 500 && gadet->speed >= SUPER_SPEED)
     mA = 900;

-- 
Baolin.wang
Best Regards