- Make heavy use of on-board LED indicators by calling ioremap() and
poking your virtualized hardware register location to flip on the LED indicators.
I strongly recommend *against* doing this, at least unless you know *exactly* what you are doing (and then you don't need this because you will use a BDI2000 anyway). I've seen to many reports of "Linux crashes when enabling the MMU" that were cause by exactly such attempts.
Oh yeah... I totally agreed on your recommendation. But when one is located FAR FAR AWAY from the cushy software laboratory and without a hardware debugger, I have find this technique extremely useful in very DARK, DARK circumstances.
Another time, I had to bring-up a custom board that is totally devoid of inputs/output interface (as those interfaces were still under HW development), this LED method saved my bacon as I SLOWLY and PAINFULLY integrate Xilinx UARTLITE driver (if one is extremely careful about setting aside a TLB region JUST for that purpose.
Alright, alright.... Let us call this LED indicators, a 'poor man's' debugger. Desperate acts calls for desperate measure.