Can't target thumbv6m-none-eabi due to AtomicBool

Hi, 
I'm targeting rp2040 but the code (slot.rs) use the AtomicBool type that have fetch_or and fetch_and functions that aren't supported on  thumbv6m (no #[cfg(target_has_atomic = "8")]).
Is your code stuck on thumbv7em or do you plan to have more targets?
Olivier