When should gpio-restart be used/avoided?

[Lech Perczak]

W dniu 2022-08-14 o 13:35, Bjørn Mork pisze:
> Bjørn Mork <bjorn at mork.no> writes:
>
>> FWIW, I did a simple test now using ModemManager on the MF286D.  There
>> is no issue with the modem after reboot, even if the gpio-restart device
>> is disabled.
>>
>> This is my MM config:
>>
>> config interface 'wan'
>>          option device '/sys/devices/platform/soc/8af8800.usb3/8a00000.dwc3/xhci-hcd.0.auto/usb2/2-1'
>>          option proto 'modemmanager'
>>          option apn 'internet.public'
>>
>>
>> I disabled the gpio-restart by doing
>>
>>   echo gpio-restart >/sys/bus/platform/drivers/restart-gpio/unbind
>>
>> Rebooting brings up the modem connection comes up just fine.  I can't
>> see anything wrong with it.
>>
>> In theory all services in a QMI modem should be reset to defaults and
>> all state cleared by simply sending a QMI_CTL SYNC request to the modem.
>> And I see that we do send this during setup in
>>
>> package/network/utils/uqmi/files/lib/netifd/proto/qmi.sh
>>
>> A bit late maybe, after PIN and framing config, but that's probably
>> fine.  At least I don't expect the SIM state to be reset by SYNC.  Don't
>> know about 802.3 framing, but I'd have to dig out an old modem to find
>> out.  I guess it will work since the framing is a persistent setting
>> IIRC.
>>
>> I'll do a test with uqmi too.
> Now tested with uqmi.  ModemManager disabled by removing the /etc/rc.d
> symlink.  gpio-restart disabled as before.  Otherwise default config
> except for this uqmi network interface:
>
> config interface 'wan'
>          option device '/dev/cdc-wdm0'
>          option proto 'qmi'
>          option apn 'internet.public'
>          option dhcp '0'
>          option autoconnect '0'
>
>
>
> I don't see any issues after rebooting multiple times.  The modem is
> re-initialised and the connection is brought up on boot.
>
> Note that I haven't tested with PIN verification enabled.  And I am
> disabling dhcp and autoconnect since these features depends on some
> buggy vendor firmware implementation. In my experience, using modem
> firmware for session management is about as good idea as running vendor
> firmware on your router... I guess these choices might affect the test
> result though.
I'll try your settings, on MF286D and on older MF286 as well.
My setup is a bit more convoluted, since my build has patches to use 
split APN for IPv4v6 dual stack and I use DHCP.
>
> But AFAICS the gpio-restart is not required for proper modem reset.  The
> modem works just fine without it.
Please check what happens if you set the "power button blocker" GPIO 
switch high instead of default low. It will block the rear power switch,
and should allow modem restart without forcing power-down of whole board 
during reboot, IIRC.
>
> Bjørn


-- 
Pozdrawiam,
Lech Perczak