<div dir="ltr"><div dir="ltr"><div class="gmail_default" style="font-size:small">Hi Paul,</div><div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">Thank yo</div><div class="gmail_default" style="font-size:small"><br></div><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr" style="color:rgb(0,0,0);font-family:Helvetica;font-size:12px"><div><b>Geert</b></div></div></div></div></div></div></div></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, 27 May 2020 at 15:34, Paul Gildea <<a href="mailto:gildeap@tcd.ie">gildeap@tcd.ie</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">HI Amol, afraid I don't know as I don't use that.<div><br></div><div>--</div><div>Paul</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, 27 May 2020 at 04:06, Amol Lad <<a href="mailto:Amol.Lad@4rf.com" target="_blank">Amol.Lad@4rf.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div lang="EN-NZ">
<div>
<p class="MsoNormal"><span>Hi Paul,<u></u><u></u></span></p>
<p class="MsoNormal"><span><u></u> <u></u></span></p>
<p class="MsoNormal"><span>Does same problem occur with MBIM as well?<u></u><u></u></span></p>
<p class="MsoNormal"><span><u></u> <u></u></span></p>
<p class="MsoNormal"><span>Amol<u></u><u></u></span></p>
<p class="MsoNormal"><span><u></u> <u></u></span></p>
<div style="border-right:none;border-bottom:none;border-left:none;border-top:1pt solid rgb(225,225,225);padding:3pt 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> libqmi-devel <<a href="mailto:libqmi-devel-bounces@lists.freedesktop.org" target="_blank">libqmi-devel-bounces@lists.freedesktop.org</a>>
<b>On Behalf Of </b>Paul Gildea<br>
<b>Sent:</b> Tuesday, 26 May 2020 6:43 PM<br>
<b>To:</b> libqmi (development) <<a href="mailto:libqmi-devel@lists.freedesktop.org" target="_blank">libqmi-devel@lists.freedesktop.org</a>><br>
<b>Subject:</b> Re: libqmi-devel Digest, Vol 102, Issue 8<u></u><u></u></span></p>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<p class="MsoNormal">Hi Geert,<u></u><u></u></p>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal">I am seeing this -71 EPROTO error on two occasions. The one I am currently seeing is happening with Telit LN960A18's. <u></u><u></u></p>
</div>
<div>
<p class="MsoNormal">We pass traffic over the modem with iperf3 and it resets after a time period with those errors, usually within 30 minutes.<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal">If I force the modem to USB2.0 it seems to not happen. I'm currently trying to find out why this is happening, I am looking at the<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal">kernel debug and am seeing a "do warm reset" debug message from the driver (hub.c) and have been trying to track down why.<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal">The second was covered in detail in another thread on here called "MTU issues", here was the finding:<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<blockquote style="border-top:none;border-right:none;border-bottom:none;border-left:1pt solid rgb(204,204,204);padding:0cm 0cm 0cm 6pt;margin-left:4.8pt;margin-right:0cm">
<p class="MsoNormal">Enabled traces for usbnet.c and xhci-ring.c file in debugfs as follows:<br>
<span><span style="font-family:"Courier New";color:rgb(80,0,80)">mount -t debugfs none /sys/kernel/debug</span></span><span style="font-family:"Courier New";color:rgb(80,0,80)"><br>
<span>echo -n 'file usbnet.c +p' > /sys/kernel/debug/dynamic_debug/control</span><br>
</span><span style="font-family:"Courier New"">echo -n 'file xhci-ring.c +p' > /sys/kernel/debug/dynamic_debug/control</span><br>
Saw a lot of errors indicating URB with len=0 when it was expecting len=1430. This was preceded by an URB of len 1024 bytes:<br>
<span style="font-family:"Courier New"">xhci_hcd 0000:00:14.0: Babble error for slot 10 ep 12 on endpoint<br>
xhci_hcd 0000:00:14.0: Giveback URB ffff8802193be540, len = 1024, expected = 1430, status = -75<br>
xhci_hcd 0000:00:14.0: Transfer error for slot 10 ep 12 on endpoint<br>
</span>/repeated<br>
Error -75 is EOVERFLOW, which makes sense as per<i> include/uapi/asm-generic/errno.h</i><br>
<span style="font-family:"Courier New"">#define EOVERFLOW 75 /* Value too large for defined data type */</span><br>
<b>"Babble error"</b>: When a packet larger than <span>MTU</span> arrives in Linux from the modem and is discarded with -EOVERFLOW error.<br>
This is seen on USB3.0 and USB2.0 busses. This is essentially because the MRU (Max Receive Size) is not a separate entity to the <span>MTU</span> (Max Transmit Size) and the received packets can be larger than those transmitted.<br>
<b>"Endless input error"</b>: Following the babble error we see an endless supply of zero-length URBs which are rejected with -EPROTO (increasing the rx input error counter each time).<br>
This is only seen on USB3.0. These continue to come ad infinitum until the modem is shutdown.<br>
There appears to be a bug in the core USB handling code in Linux that doesn't deal well with network <span>MTUs</span> smaller than 1500 bytes. By default the dev->hard_mtu (the "real" <span>MTU</span>) is in lockstep with
dev->rx_urb_size (essentially an MRU), and it's the latter that is causing trouble. This has nothing to do with the modems; the issue can be reproduced by getting a USB-Ethernet dongle, setting the <span>MTU</span> to 1430, and pinging with
size greater than 1406.<br>
Will submit the below patch that solves the issue, if that is acceptable?<br>
<span style="font-family:Arial,sans-serif"><br>
+diff -Naur linux-4.14.73/drivers/net/usb/qmi_wwan.c linux-4.14.73-rx_size_fix/drivers/net/usb/qmi_wwan.c<br>
+--- linux-4.14.73/drivers/net/usb/qmi_wwan.c 2018-09-29 11:06:07.000000000 +0100<br>
++++ linux-4.14.73-rx_size_fix/drivers/net/usb/qmi_wwan.c 2020-01-31 18:05:07.709008785 +0000<br>
+@@ -740,6 +740,14 @@<br>
+ }<br>
+ dev->net->netdev_ops = &qmi_wwan_netdev_ops;<br>
+ dev->net->sysfs_groups[0] = &qmi_wwan_sysfs_attr_group;<br>
++<br>
++ /* LTE Networks don't always respect their own <span>MTU</span> on receive side;
<br>
++ * e.g. AT&T pushes 1430 <span>MTU</span> but still allows 1500 byte packets from
<br>
++ * far-end network. Make receive buffer large enough to accommodate<br>
++ * them, and add four bytes so <span>MTU</span> does not equal MRU on network<br>
++ * with 1500 <span>MTU</span> otherwise usbnet_change_mtu() will change both.<br>
++ * This is a sufficient max receive buffer as over 1500 <span>
MTU</span>, <br>
++ * USB driver issues are not seen.<br>
++ */<br>
++ dev->rx_urb_size = ETH_DATA_LEN + 4;<br>
+ err:<br>
+ return status;<br>
+ }</span><u></u><u></u></p>
</blockquote>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal">I submitted this fix to the kernel but you just reminded me that it was rejected due to formatting and I completely forgot to resubmit.<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal">--<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal">Paul <u></u><u></u></p>
</div>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<div>
<p class="MsoNormal">On Tue, 26 May 2020 at 13:00, <<a href="mailto:libqmi-devel-request@lists.freedesktop.org" target="_blank">libqmi-devel-request@lists.freedesktop.org</a>> wrote:<u></u><u></u></p>
</div>
<blockquote style="border-top:none;border-right:none;border-bottom:none;border-left:1pt solid rgb(204,204,204);padding:0cm 0cm 0cm 6pt;margin-left:4.8pt;margin-right:0cm">
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Today's Topics:<br>
<br>
1. USB errors with qmi-wwan (Geert Lens)<br>
<br>
<br>
----------------------------------------------------------------------<br>
<br>
Message: 1<br>
Date: Mon, 25 May 2020 15:42:56 +0200<br>
From: Geert Lens <<a href="mailto:g.lens@livetech-systems.com" target="_blank">g.lens@livetech-systems.com</a>><br>
To: <a href="mailto:libqmi-devel@lists.freedesktop.org" target="_blank">libqmi-devel@lists.freedesktop.org</a><br>
Subject: USB errors with qmi-wwan<br>
Message-ID:<br>
<CAOCF0GO7xCyfRyTJmJnT=<a href="mailto:iZ9MoDCo6XL1Fa0YrOZz5GWm-%2Bd3g@mail.gmail.com" target="_blank">iZ9MoDCo6XL1Fa0YrOZz5GWm-+d3g@mail.gmail.com</a>><br>
Content-Type: text/plain; charset="utf-8"<br>
<br>
Hi,<br>
<br>
We are using the QMI interface on the Quectel BG96 modem and everything<br>
works fine, but after a few hours the connection is suddenly disconnected<br>
and the qmi_proxy starts hogging CPU.<br>
<br>
During this time the USB interfaces of the modem are not responding and<br>
will only work again after the modem is physically turned off and on.<br>
<br>
Output from dmesg:<br>
<br>
*qmi_wwan 1-1:1.4: nonzero urb status received: -71*<br>
*qmi_wwan 1-1:1.4: wdm_int_callback - 0 bytes*<br>
*qmi_wwan 1-1:1.4: nonzero urb status received: -71*<br>
*qmi_wwan 1-1:1.4: wdm_int_callback - 0 bytes*<br>
*qmi_wwan 1-1:1.4: nonzero urb status received: -71*<br>
*qmi_wwan 1-1:1.4: wdm_int_callback - 0 bytes*<br>
*qmi_wwan 1-1:1.4: nonzero urb status received: -71*<br>
*qmi_wwan 1-1:1.4: wdm_int_callback - 0 bytes*<br>
<br>
I have read that the -71 (EPROTO) is mostly caused by hardware or firmware<br>
issues and that it can cause the kernel to disable the device, is<br>
this correct? Or could it be something else?<br>
<br>
Version used:<br>
- Linux kernel: v4.14.78<br>
- ModemManager: v1.12.10<br>
- libqmi: v1.24.10<br>
<br>
*Geert*<br>
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********************************************<u></u><u></u></p>
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