Benjamin Herrenschmidt <b...@kernel.crashing.org> writes: > On Tue, 2017-06-13 at 20:04 +1000, Michael Ellerman wrote: >> > Good idea. Writing to CTRL register can change only the RUN field. >> > Was this any different in older generations? >> >> No AFAICS back to 2.02. >> >> > Anton and Ben kept the mfspr/mtspr part in earlier updates to this >> > routine. >> >> Doing the read/modify write is forward compatible vs a new writable >> field, whereas writing the whole register with a known value is not. > > At this stage I wouldn't worry too much about it. What we can do is > write a pre-cooked value (from reading it earlier once at boot) if we > are paranoid or just do what Nick does and put the onus on future > designs that might want to re-use it for other things to add a mode > bits to configure the new feature in.
Fine by me. cheers