The or1k-elf toolchain contains the standard C library (printf, malloc, etc.). But beside this, it also contains a large set of function that help the baremetal programmer with controlling the processor, shortly summarized as or1k-support.

Getting Started

The most important functions are defined in the or1k-support.h header file. For example, three macros are defined there to access memory-mapped registers: REG8(x), REG16(x) and REG32(x). Those are for example helpful if you control a device that is connected to the bus and the compiler should not reuse previously loaded values (the macros expand to pointers to volatile values).

Example:

#include <or1k-support.h>
...
#define MY_DEVICE_READ_REG 0xf0000000
...
void getchars(char* x, int num) {
    int i;
    for (i = 0; i < num; i++) {
	x[i] = REG8(MY_DEVICE_READ_REG);
    }
}

Cache handling

The caches can be controlled by a set of functions. To disable the data cache for a certain period of time, then flush this value from the cache and re-activate the cache (for non-coherent memory accesses), you can for example execute:

#include <or1k-support.h>
...
void f(int *a) {
    or1k_dcache_disable();
    ...
    /* your fancy non-coherent stuff via a */
    ...
    or1k_dcache_flush(a);
    ...
    or1k_dcache_enable();
}