SIM7600SA-H: SIM card detection issues in OpenWrt

[Yegor Yefremov]

I experienced the following issue when working with SIM7600SA-PCIE in
OpenWrt running from a NAND partition. As soon as the modem is
detected, I get the card's information via "mmcli -m 0":

 Hardware |      manufacturer: QUALCOMM INCORPORATED
           |             model: 0
           | firmware revision: LE11B13SIM7600M22
           |    carrier config: default
           |      h/w revision: 10000
           |         supported: gsm-umts, lte
           |           current: gsm-umts, lte
           |      equipment id: 868020030145634
  -----------------------------
  System   |            device:
/sys/devices/platform/ocp/47400000.target-module/47401400.usb/musb-hdrc.0/usb1/1-1/1-1.3
           |           physdev:
/sys/devices/platform/ocp/47400000.target-module/47401400.usb/musb-hdrc.0/usb1/1-1/1-1.3
           |           drivers: qmi_wwan
           |            plugin: simtech
           |      primary port: cdc-wdm0
           |             ports: cdc-wdm0 (qmi), wwan0 (net)
  -----------------------------
  Status   |             state: failed
           |     failed reason: sim-missing
           |       power state: on
........
SIM      |  primary sim path: /org/freedesktop/ModemManager1/SIM/0
           |    sim slot paths: slot 1:
/org/freedesktop/ModemManager1/SIM/0 (active)
           |                    slot 2: none

Then, I perform a modem reset: mmcli -m 0 -r and the SIM card is working.

When I start the same rootfs from an SD card, everything is working as
expected. Hence, this seems to depend on the lower speed of the NAND
boot medium.

My system:

Linux 6.1.62
OpenWrt: SNAPSHOT r24436-0f283ab4c9 (v23.05.2)
mmcli 1.22.0

Any idea what's going wrong and how to fix this behavior?

Regards,
Yegor