netdev - Re: [PATCH 1/1] drivers: net: usb: qmi_wwan: add QMI_QUIRK_SET

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Date:   Wed, 19 Apr 2017 21:39:20 +0200
From:   Bjørn Mork <bjorn@...k.no>
To:     Aleksander Morgado <aleksander@...ksander.es>
Cc:     Daniele Palmas <dnlplm@...il.com>,
        "netdev\@vger.kernel.org" <netdev@...r.kernel.org>,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH 1/1] drivers: net: usb: qmi_wwan: add QMI_QUIRK_SET_DTR for Telit PID 0x1201

Aleksander Morgado <aleksander@...ksander.es> writes:

> On Wed, Apr 19, 2017 at 7:28 PM, Bjørn Mork <bjorn@...k.no> wrote:
>>> as a side note in latest kernels I had troubles with qmi devices
>>> (e.g. I/O error when using qmicli).
>>>
>>> I found your suggestion in libqmi mailing list to revert commit
>>>
>>> 833415a3e781a26fe480a34d45086bdb4fe1e4c0
>>> cdc-wdm: fix "out-of-sync" due to missing notifications
>>
>> I guess a revert of that commit should be done then..
>>
>> I have been stalling because I have been hoping to replace it with a
>> better fix instead of a plain revert. I believe there are several issues
>> playing badly together here.  That commit was _expected_ to cause
>> spurious EPIPE errors, which would be translated to EIO if they were
>> propagated.  But they should be filtered out rightaway, in theory. This
>> works for me.  I can see the EPIPEs with debugging, but I have never
>> seen any EIO from read.
>>
>> And there is the problem: I am unable to reproduce this problem.  I have
>> previously tested this back and forth with several MDM9200 and MDM9235
>> generation modems in QMI mode, as well as in MBIM mode.  And also with a
>> number of other MBIM modems.  Aleksander reported that he could
>> reproduce the issue using an MDM9x15 generation modem in QMI mode, but
>> not with any MDM9x00 or MDM9x35 modem.  So I have now tried any way I
>> can imagine to reproduce the issue with a Sierra Wireless EM7305, which
>> is the only MDM9x15 modem I have. The firmware is SWI9X15C_05.05.58.00.
>>
>> But unfortunately the testing is still without "success".  It plain
>> works for me, every time, using ModemManager, qmicli with or without
>> proxy, or uqmi.
>>
>> Would you mind describing in detail how you trigger the EIOs?  What
>> software and command sequence are you using?  Does it reliably reproduce
>> the issue, or do you have to try several times?  What modem chipset and
>> firmware is used?
>
> Reliably, as in the second command I sent already showed the issue :/
> I meant to try to debug this issue myself a while ago, but got busy
> with other stuff, as usual... This is with a Sierra Wireless MC7304
> running SWI9X15C_05.05.67.00. If you want, I can give you SSH access
> to a system with this modem plugged in, or I can even send you a spare
> MC7354, whatever you prefer.

I don't think another modem would help.  The EM7305 should be the same
as an.MC7304 or MC7354 in this regard.

And the ssh access would only help if I knew what to look for.  I think
you can do this just as well as me...  


> I'm just running --dms-get-operating-mode multiple times, and getting
> errors frequently:
>
> aleksander@...ena:~/Development/foss/libqmi:(master)$ sudo qmicli -d
> /dev/cdc-wdm3 --dms-get-operating-mode
> [/dev/cdc-wdm3] Operating mode retrieved:
> Mode: 'online'
> HW restricted: 'no'
>
> aleksander@...ena:~/Development/foss/libqmi:(master)$ sudo qmicli -d
> /dev/cdc-wdm3 --dms-get-operating-mode
> [19 abr 2017, 20:25:36] -Warning ** Error reading from istream: Error
> reading from file descriptor: Input/output error
> ^[[A^Ccancelling the operation...
> error: couldn't create client for the 'dms' service: Operation was cancelled

Lucky you :)

I upgraded the EM7305 to SWI9X15C_05.05.67.00 and tried again.  No
difference.  I ran

 for i in `seq 1 1000`; do qmicli -d /dev/cdc-wdm1 --dms-get-operating-mode; done

without a single error.  I guess I'll go for the revert.

But I think we need to do something about commit c1da59dad0eb as
well. It can end up calling usb_submit_urb(desc->response, GFP_KERNEL)
from an URB callback.  And making the rerr update conditional doesn't
seem right either.  It changes the meaning of rerr from "last status" to
"first error", which means that any error will mask a later success
until userspace reads the error.  That's fishy.


Bjørn