linux-6.6.y: ts7553v2: Failure to reboot under specific conditions #249
Description
TS-7553-V2 (and potentially other i.MX6UL platforms) fail to reboot from the 6.6 kernel (potentially all LTS kernels) if booted to U-Boot and reset is used to reset the system from U-Boot.
Likely, since both U-Boot and the kernel use the CPU WDT to reboot, a U-Boot reset puts the WDT in a state that the kernel doesn't reset from and fails to be able to use to trigger a reset.
If all power is removed, the unit is booted to Linux, and then reboot is issued there, the unit will reboot without issues. However, if booted to U-Boot and then reset is used there, then any further boots to Linux will see reboot continually fail.
Testing has found that some units will still reboot after some amount of time (about 90 s), whereas other units seem to never reboot (10 min +).
This is not reproducible in the stock 4.1 kernel. This is likely for a combination of reasons that this kernel is from NXP and it uses the microcontroller WDT in Linux rather than the CPU WDT.