Hi,
Yes, I can confirm, this is used to reset the modem on rebooting the device.
At least when used in conjunction with uqmi, the modem would misbehave
otherwise,
and connection attempts would fail after rebooting the device. The same
is true for its ath79-based predecessors.
I think this issue deserves investigation on its own.
Issue with this pin is that if we'd just like to reset the modem, it's
not possible without resetting the device,
as this is basically a "suicide switch" rather than just USB power cutoff.
Kind regards,
Lech
W dniu 2022-08-13 o 22:48, Robert Marko pisze:
I had just that question today when reviewing a similar ZTE modem.
It appears that its to reset the modem as well:
https://github.com/openwrt/openwrt/pull/10418/files#r945125301
Regards,
Robert
On Sat, 13 Aug 2022 at 19:13, Bjørn Mork <bj...@mork.no> wrote:
I just got myself a ZTE286D. But after installing OpenWrt I had an
unexpected problem on reboot. The Openwrt DTS includes a gpio-restart
device:
gpio-restart {
compatible = "gpio-restart";
gpios = <&tlmm 8 GPIO_ACTIVE_HIGH>;
};
The gpio-restart driver is therefore used to reboot the system due to
default priorities.
I have two concerns about this:
1) it's different from OEM, and
2) it cuts power to the 3.3V VCC console line on reboot
A quick test indicates that reboot works just fine without using
gpio-restart in OpenWrt too. And a similar node seems to be rare in
this target. AFAICS, this is the only device having one.
So I wonder if we could/should remove that gpio-restart device. What do
you think?
The reason I ask is because the VCC toggling causes unnecessary problems
for me. I realize that I have an unusual setup, but I have connected a
bluetooth module to the console port. Toggling the console VCC on
reboot makes it hard/imposible to enter the bootloader, or to capture
the whole boot log. It takes some time before the console server
notices that the bluetooth device disappeared and tries to reconnect. I
believe this is an unwanted side effect. And it wasn't like that with
OEM.
This is of course only a minor problem. In addition to just pathcing the
DTS myself, I could also put something like
test -w /sys/bus/platform/drivers/restart-gpio/unbind && echo gpio-restart
>/sys/bus/platform/drivers/restart-gpio/unbind
into /etc/rc.local. That's a perfectly fine workaround. But I wanted
to ask becasuse of the different behaviour in OEM.
Bjørn
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Pozdrawiam,
Lech Perczak
lech.perc...@gmail.com
Mobile: +48 694 309 185
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