EIO errors on SWI9200 modules

[Aleksander Morgado]

On Tue, Mar 21, 2017 at 3:19 PM, Bjørn Mork <bjorn at mork.no> wrote:
>>
>> I'm running Linux kernel 4.9.11, and getting a bunch of weird EIO
>> errors randomly doing QMI operations with modems of the MC73xx family
>> (SWI9200); I've tested MC7304, MC7330 and MC7354 with new and old
>> firmwares. I cannot reproduce this issue with MC71xx (SWI9x15) or
>> MC74xx (SWI9x30) modules.
>
> Thanks! That cleared up quite a bit. Looks like I've been using MC74xx
> modules too much lately.
>
> Still a bit confused though: The MC73xx series use MDM9x15 chips.  The
> MDM9x00 chips were used by the older MC77xx series.  I did test a modem
> with MDM9200 lately (the Huawei E392), but could not reproduce the
> problem there.  But if you really meant to say that the problem only
> affects the MDM9x15 generation, then my results are consistent with
> that.  Haven't tested any of those modems in a long time
>

Wow, yeah, sorry for the mixup. The error happens in 9x15 chips
(MC73xx); doesn't happen in 9200 chips (older MC77xx). I've been doing
too many FW upgrades myself lately, too many numbers...

>> Reproducible easily with e.g.:
>>
>> $ while [ 1 ]; do sudo qmicli -d /dev/cdc-wdm2 --dms-get-operating-mode; done
>> [21 mar 2017, 14:53:18] -Warning ** Error reading from istream: Error
>> reading from file descriptor: Input/output error
>> error: couldn't create client for the 'dms' service: CID allocation
>> failed in the CTL client: Transaction timed out
>> [/dev/cdc-wdm2] Operating mode retrieved:
>> Mode: 'online'
>> HW restricted: 'no'
>> [/dev/cdc-wdm2] Operating mode retrieved:
>> Mode: 'online'
>> HW restricted: 'no'
>> [/dev/cdc-wdm2] Operating mode retrieved:
>> Mode: 'online'
>> HW restricted: 'no'
>> [21 mar 2017, 14:53:29] -Warning ** Error reading from istream: Error
>> reading from file descriptor: Input/output error
>> ...
>>
>> I was going to ask if this has ever been seen before, as it was new to
>> me in my memory, and then I googled for it and found this old thread:
>>
>> https://lists.freedesktop.org/archives/libqmi-devel/2014-March/000734.html
>>
>> Quoting Bjørn:
>>
>> "What we know is:
>>
>>  - At some point wdm_in_callback() is called with urb->status == -EPIPE.
>>  - the pending wdm_read() sees desc->rerr being non-zero (-EPIPE) and
>>    returns -EIO to userspace"
>>
>> It's a bit unfortunate, because on -EIO we force the QmiDevice to get
>> closed. Is there a better way to handle this? If there's nothing to
>> fix in the kernel-side, should we maybe ignore -EIO errors and just
>> warn about them, nothing else?
>
> I think the problem you see is newer than that, and caused either by my
> commit 833415a3e781 ("cdc-wdm: fix "out-of-sync" due to missing
> notifications"), or by a combination of that with commit  c1da59dad0eb
> ("cdc-wdm: Clear read pipeline in case of error")

I'll try reverting those and see what happens later tonight, unless
you're quicker :9

-- 
Aleksander
https://aleksander.es