linux-kernel - Re: [PATCH] usb: cdns3: gadget: Don't manage pullups

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Date:   Fri, 25 Oct 2019 13:14:33 +0300
From:   Felipe Balbi <balbi@...nel.org>
To:     Roger Quadros <rogerq@...com>, Peter Chen <peter.chen@....com>,
        Pawel Laszczak <pawell@...ence.com>
Cc:     "felipe.balbi\@linux.intel.com" <felipe.balbi@...ux.intel.com>,
        "gregkh\@linuxfoundation.org" <gregkh@...uxfoundation.org>,
        "nsekhar\@ti.com" <nsekhar@...com>,
        Rahul Kumar <kurahul@...ence.com>,
        "linux-usb\@vger.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: cdns3: gadget: Don't manage pullups


Hi,

Roger Quadros <rogerq@...com> writes:
> On 25/10/2019 06:13, Peter Chen wrote:
>> On 19-10-23 09:17:45, Pawel Laszczak wrote:
>>> Hi,
>>>
>>> Reviewed-by: Pawel Laszczak <pawell@...ence.com>
>> 
>> Hi Roger & Pawel,
>> 
>> Assume gadget function has already enabled, if you switch host mode
>> to device mode, with your changes, where the device mode will be enabled
>> again?
>
> When it switches from device mode to host the UDC is removed. When we switch
> back from host to device mode the UDC is added, so,
>
> usb_add_gadget_udc_release()-> check_pending_gadget_drivers()->
> udc_bind_to_driver()->usb_udc_connect_control()->usb_gadget_connect()->
> gadget->ops->pullup()

I agree with Roger here. UDC shouldn't try to manage pullups
directly. If there are any bugs related to role switch, we should fix it
in udc core, so the fix applies to everyone ;-)

-- 
balbi

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