Do modern diesels (talking pickup trucks here) regulate the RPM during warmup (I've got a 2009 Mazda 3 which goes to high "idle" RPM for a short time after starting)?
My '97 idles at like 700 rpm or something which I doubt is enough to actually warm up an engine - I believe if you idle at that rate long-term you'll get wet stacking which tells me it probably isn't particularly warm; I do have an aftermarket mode that will bump the RPM to 1200 which I switch to for a warmup if it's actually cold-ish here (it's never cold here), or if I'm using the winch.
I park my tractor in a container and while it's backed in with the exhaust pointed mostly forward at the open door, I still don't want to sit there waiting for a warmup, so I usually start it, wait about 30 seconds, bump up the throttle a bit above 1000, then very slowly pull out, and in the next couple minutes I'm hooking up whatever I need to the tractor and occasionally bump up the throttle till it's about 1500 as I go where I'm going to be working. Usually a few minutes before I'm ready to work at the specific site which seems enough for a decent warmup.