TPS53603A deadtime control

This is about the adaptive deadtime control of TPS53603A.

1）In the function diagram， SW and HDR are the input signal of the comparator，VTH and HDR are the signal of the comparator. Could you tell me about the purpose of the both comparators? It seems about the deadtime?

2) In the paragraph about adaptive deadtime control, it just explain how to control the tr-DT. How about the tf-DT? Could you explain it?

3) In the paragraph about adaptivd deadtime control, a proper threshold is ?

Thanks a lot.