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Date:   Fri, 21 Dec 2018 16:05:04 +0000
From:   John Keeping <john@metanate.com>
To:     Minas Harutyunyan <minas.harutyunyan@synopsys.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "arthur.petrosyan@synopsys.com" <arthur.petrosyan@synopsys.com>
Subject: Re: [PATCH] usb: dwc2: gadget: fix ISOC frame overflow handling
Message-ID: <20181221160504.15e93827@donbot>
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Hi Minas,

On Wed, 19 Dec 2018 14:09:01 +0000
Minas Harutyunyan <minas.harutyunyan@synopsys.com> wrote:

> On 12/18/2018 6:35 PM, John Keeping wrote:
> > Hi Minas,
> > 
> > On Fri, 14 Dec 2018 09:00:08 +0000
> > Minas Harutyunyan <minas.harutyunyan@synopsys.com> wrote:  
> >> First of all, sorry for delayed answer.
> >> Looks like similar issue seen by Andrzej Pietrasiewicz
> >> <andrzej.p@samsung.com>: "dwc2 isochronous transfers issues". Same
> >> feedback provided to Andrzej.
> >>
> >> I run tests on 4.20.0-rc4 in DDMA. By default IN ISOC traffic
> >> failed because of BNA interrupts. It's happen because UAC2
> >> requests count set by default to 2. Our core and driver can't work
> >> in DDMA with descriptor list length equal to 2. It's not possible
> >> on time prepare next descriptors to avoid BNA interrupt.
> >>
> >> By changing UAC2_DEF_REQ_NUM to 4 all audio gadget tests passed
> >> smoothly. Could you please apply this patch and run tests in DDMA
> >> mode:
> >>
> >> diff --git a/drivers/usb/gadget/function/u_uac2.h
> >> b/drivers/usb/gadget/function/u_uac2.h
> >> index 8362ee572e1e..5e649259ab76 100644
> >> --- a/drivers/usb/gadget/function/u_uac2.h
> >> +++ b/drivers/usb/gadget/function/u_uac2.h
> >> @@ -21,7 +21,7 @@
> >>    #define UAC2_DEF_CCHMASK 0x3
> >>    #define UAC2_DEF_CSRATE 64000
> >>    #define UAC2_DEF_CSSIZE 2
> >> -#define UAC2_DEF_REQ_NUM 2
> >> +#define UAC2_DEF_REQ_NUM 4
> >>
> >>    struct f_uac2_opts {
> >>           struct usb_function_instance    func_inst;
> >>
> >>
> >> If it will OK on your side also then will switch to BDMA mode and
> >> debug.  
> > 
> > With DDMA enabled, I see the following error after the stream has
> > been running for a while (anything from a few seconds to a few
> > minutes): 
> > -- >8 --  
> > [ 1798.836322] dwc2 ff580000.usb: dwc2_hsotg_ep_disable: called for
> > ep0 [ 1798.836329] dwc2 ff580000.usb: dwc2_hsotg_ep_disable: called
> > for ep0 [ 1798.851092] dwc2 ff580000.usb: new device is high-speed
> > [ 1798.924461] dwc2 ff580000.usb: new device is high-speed
> > [ 1798.982887] dwc2 ff580000.usb: new address 25
> > [ 1799.002463] configfs-gadget gadget: high-speed config #1: config
> > -- 8< --
> > 
> > On the host side (Linux 4.18.16 Intel xHCI), I see this logged at
> > the same time:
> >   
> > -- >8 --  
> > [1735740.716242] retire_capture_urb: usb 1-2.2.7: frame 0 active:
> > -71 [1735740.716990] retire_capture_urb: usb 1-2.2.7: frame 0
> > active: -71 [1735740.717906] retire_capture_urb: usb 1-2.2.7: frame
> > 0 active: -71 [1735740.718905] retire_capture_urb: usb 1-2.2.7:
> > frame 0 active: -71 [1735740.719916] retire_capture_urb: usb
> > 1-2.2.7: frame 0 active: -71 [1735740.720032] usb 1-2.2-port7:
> > disabled by hub (EMI?), re-enabling... [1735740.720036] usb
> > 1-2.2.7: USB disconnect, device number 28 [1735740.937500] usb
> > 1-2.2.7: new high-speed USB device number 29 using xhci_hcd -- 8< --
> > 
> > The device does then enumerate and works for a period of time
> > before the same error happens again.
> >   
>  From logs not clear who initiate disconnect: host or device.  More 
> probably host, after some errors in retire_capture_urb initiate 
> disconnect. Do you have any idea?
> Can't you connect device to host on same platform?
> If root cause of disconnect by host is device issue, i.e. not able to 
> send to host data packets in time then I need device side dmesg log
> with debug enabled. USB trace around the disconnect will help to
> debug.

I remember running a test with a hardware USB analyzer and which showed
an isochronous packet with an incorrect length (much larger than it
should have been) when the failure occurred.

I don't have any logs from that test and I'm out of the office at the
moment, but I will capture logs when I'm back in January.


Thanks,
John