Unable to reboot BPI-R4 when two AW7915-NP1 are installed

Banana Pi Router design BPI-R4/BPI-R4 Pro(MT7988)
1

I have installed two AW7915-NP1 modules into my BPI-R4, which is running OpenWRT 24.10.4. After installing kmod-mt7915e and kmod-mt7915-firmware, both cards work fine. However, the reboot command does not work.

When only one module is installed (in either of the two slots), reboot works as expected. But when both modules are installed, issuing the reboot command causes the device to hang, it never starts booting again. When kmod-mt7915e is not installed, the reboot works even when both cards are plugged in (although they obviously cannot be used in that case).

I probed the board and found that the PMIC (U6, MT6682A) stops operating. It still receives the +12VD input, but produces no output. This also explains why pressing the reset button has no effect. The power must be physically disconnected and reconnected to start the board again.

Any ideas how that could happen?

2

After some additional probing, I found that the PMIC is shutting down due to overvoltage protection on buck 4 (DVDD1V8_SOC). When the router is supposed to reboot, the voltage on that rail rises quickly, triggering the OVP. I’m not sure where this is coming from. In the public portion of the schematic, I don’t see any way this could happen. Unfortunately, the schematic is missing the section that powers the main SoC, so I’m unable to debug this any further.

3

Without the wireless drivers loaded, does the reset button work for you (in 24.10.4) ?

I notice the reset button never works in OpenWrt Snapshot (master branch). And the behaviour is exactly what you’ve observed.