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

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Date:   Wed, 30 Oct 2019 01:15:16 +0000
From:   Peter Chen <peter.chen@....com>
To:     Roger Quadros <rogerq@...com>
CC:     Pawel Laszczak <pawell@...ence.com>,
        "felipe.balbi@...ux.intel.com" <felipe.balbi@...ux.intel.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "nsekhar@...com" <nsekhar@...com>,
        Rahul Kumar <kurahul@...ence.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: cdns3: gadget: Don't manage pullups

On 19-10-29 11:37:31, Roger Quadros wrote:
> 
> 
> On 29/10/2019 05:12, Peter Chen wrote:
> > On 19-10-25 12:59:17, Roger Quadros wrote:
> > > Peter,
> > > 
> > > 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()
> > 
> > Thanks. I have another question how you decide when to store UDC name
> > to /sys/kernel/config/usb_gadget/g1/UDC? Do you have a user daemon program
> > to monitor VBUS or external connector? At host mode, the store operation
> > will fail due to there is NO UDC.
> > 
> 
> Yes, user space needs to monitor /sys/class/usb_role/6000000.usb-role-switch/role
> 
> When it becomes "device" the UDC is available and it can prepare to configure
> the UDC.
> 
> Could you please give your Ack for this patch if it is OK? Thanks.
> 

Acked-by: Peter Chen <peter.chen@....com>

-- 

Thanks,
Peter Chen