Time may pass before dmactive becomes high.

[Tim Newsome (timsifive)]

This addresses a concern of how the debugger can know when hardware is
ready to be debugged, discussed on the mailing list. subject:"Email
discussion: how can a debugger know when a target is ready for it?"

[Paul Donahue (pdonahue-ventana)]

This isn't really crucial but I find this sentence to be a little less formal than specs normally are (like "long time" and what does it mean for "debugging to take place"). How about something like:
"Hardware may postpone setting this bit until it is in a state that allows further debugger accesses."
or combining with a rewrite of the previous sentence:
"After this bit is written with 1, the bit will continue to be seen by reads as being 0 until the hardware is in the defined post-reset state. Therefore, after writing 1 the debugger should poll \RdmDmcontrol until it observes that it is set."
(because the debugger shouldn't just read it once, it should poll until set)

[Ernie Edgar (ernie-sifive)]

Or "After writing 1, the debugger should poll Dmcontrol until dmactive is high. Hardware may take an arbitrarily long time to initialize and will indicate completion by setting dmactive to 1."

[Paul Donahue (pdonahue-ventana)]

Perfect.