/* 
** From: David Mosberger <davidm@napali.hpl.hp.com>
** To: ia64_rd@ldl.fc.hp.com
** Subject: [ia64 R&D] linux utility to tweak Pluto prefetch
** Date: Fri, 10 May 2002 15:32:18 -0700
**
** If you're tired of having to reboot just to tweak the Pluto prefetch
** setting, you might like the attached utility.  Use, e.g., like this:
**
**	# mmio fed09420 0000087b58a418a3
**
** where fed09420 is the address to poke and 0000087b58a418a3 is the
** new value to write.  The utility isn't limited to poking Pluto
** registers: it will poke *any* kernel address, so use with care!
**
**	--david
*/

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <sys/mman.h>

int main(int argc, char **argv)
{
	int fd = open("/dev/mem", O_RDWR | O_SYNC);
	unsigned long i, addr, val, offset, old, page_size = getpagesize();
	volatile unsigned long *mem;

	if (fd < 0)
		perror("open");

	if (argc < 3)
		exit(-2);

	addr = strtol(argv[1], NULL, 16);
	val = strtol(argv[2], NULL, 16);

	offset = addr & ~(page_size - 1);
	i = (addr - offset) / sizeof(mem[0]);

	mem = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset);
	if (mem == MAP_FAILED) {
		perror("memmap");
		exit(-1);
	}

	old = mem[i];
	printf("%016lx -> %016lx\n", old, val);
	mem[i] = val;

	return 0;
}