From: Peter Chen <Peter.Chen@freescale.com>
To: "Baxter, Jim" <jim_baxter@mentor.com>
CC: Robert Baldyga <r.baldyga@samsung.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "Zapolskiy, Vladimir" <Vladimir_Zapolskiy@mentor.com>,
        "balbi@ti.com" <balbi@ti.com>
Subject: RE: usb: gadget: f_fs: O_NONBLOCK waits MAX_SCHEDULE_TIMEOUT
Thread-Topic: usb: gadget: f_fs: O_NONBLOCK waits MAX_SCHEDULE_TIMEOUT
Thread-Index: AQHQa+QM1XzjMiA4I0uYsSeURtZl8503zcKAgACdKYCAAPn8AIBOw8CAgAQazSCAC/PigIAAsWFQ
Date: Tue, 2 Jun 2015 03:01:12 +0000
Message-ID: <BN3PR0301MB08494846EDC5DB72C6E14A0D81B50@BN3PR0301MB0849.namprd03.prod.outlook.com>
References: <551AED33.2040206@mentor.com> <551BA70B.1090706@samsung.com>
 <551C2AE1.9000608@mentor.com> <20150402002348.GA10964@shlinux2>
 <555F0F29.1070108@mentor.com>
 <BN3PR0301MB084914E934D705427A81EE4681CD0@BN3PR0301MB0849.namprd03.prod.outlook.com>
 <556C8773.9070702@mentor.com>
In-Reply-To: <556C8773.9070702@mentor.com>
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> >>>>
> >>>> Thank you, that sounds like the best approach.
> >>>> In this case I think perhaps the long wait without any data is an
> >>>> problem with the imx6 Chipidea USB controller.
> >>>
> >>> What's the possible problem?
> >>
> >> Sorry for the delay in replying, I have been getting some more
> >> details with a USB Analyser.
> >>
> >> The scenario is that the NCM  device is enumerating so we see the
> messages to:
> >>
> >> SetAddress (1)
> >> GetDescriptor (Device)
> >> GetDescriptor (StringN)
> >> GetDescriptor (Configuration)
> >> SetConfiguration (1)
> >> GetDescriptor (String iInterface)
> >> GetDescriptor (String iInterface)
> >>
> >> At this point the NCM host sends Writes to the F_FS EP0 but for some
> >> reason the host device does not respond and only issues SOF packets
> >> for hours. This happens occasionally and is fixed by turning the device off
> and on again.
> >>
> >>
> >
> > We may find this 'some reason', is it device error or host error?
> >
> > Do you have below patch in your code:
> >
> > commit 953c66469735aed8d2ada639a72b150f01dae605
> > Author: Abbas Raza <Abbas_Raza@mentor.com>
> > Date:   Thu Jul 17 19:34:31 2014 +0800
> >
> >     usb: chipidea: udc: Disable auto ZLP generation on ep0
> >
> >     There are 2 methods for ZLP (zero-length packet) generation:
> >     1) In software
> >     2) Automatic generation by device controller
> >
> >     1) is implemented in UDC driver and it attaches ZLP to IN packet if
> >        descriptor->size < wLength
> >     2) can be enabled/disabled by setting ZLT bit in the QH
> >
> > Peter
> 
> Yes I have that patch, could that be a problem?
> 

No, you need that patch.
Get to know which side has problem first.

Peter

> Jim
> 
> >
> >> Unless I am mistaken from a NCM gadget point of view the attached
> >> device is working correctly and there is no way to know it has failed, is that
> correct?
> >>
> >>>
> >>>>
> >>>> I guess it should suspend and drop the connections if there is no
> >>>> traffic for more than 10ms?
> >>>>
> >>>
> >>> If the Device side NAK host's IN/OUT token continually, the pipe
> >>> will not be stopped, the host will send token continually until the
> >>> application cancel this request.
> >>>
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