nixos-riscv/tools/plictool.c

/* Copyright (c) 2024 Barcelona Supercomputing Center (BSC)
 * SPDX-License-Identifier: MIT
 * Author: Rodrigo Arias Mallo <rodrigo.arias@bsc.es> */

/* Small utility to dump the state of the PLIC. */

/* Changelog:
 *   v0.0.1 (2024-09-03): Initial version.
 *   v0.0.2 (2024-09-04): Print contexts in another line and masked information.
 *   v0.0.3 (2024-09-04): Make output format more clear and add manual.
 *   v0.0.4 (2024-09-30): Implement support for claiming an interrupt.
 */

#define VERSION "v0.0.4"

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <errno.h>

enum op { DUMP, CLAIM } operation = DUMP;
const char *plic_address_str = "0x40800000";
long ncontexts = 15872L;
long maxsources = 1024L;
long nsources = 1024L;
long claim_ctx = 0;

static void
usage(void)
{
	printf(
"NAME\n"
"    plictool - dump PLIC information\n"
"\n"
"SYNOPSIS\n"
"    plictool [-a addr] [-s nsources] [-c ncontexts] [-C ctx]\n"
"\n"
"DESCRIPTION\n"
"    Dumps information about the RISC-V PLIC interrupt controller.\n"
"    Optional arguments:\n"
"\n"
"      -a addr        The starting address of the PLIC.\n"
"                     The default is 0x40800000.\n"
"\n"
"      -s nsources    Limit the number of sources to print.\n"
"                     The default is 1024.\n"
"\n"
"      -c ncontexts   Limit the number of contexts to print.\n"
"                     The default is 15872.\n"
"\n"
"      -C ctx         Claim the interrupt on the given context.\n"
"\n"
"OUTPUT FORMAT\n"
"    Information is printed for each source that has some bit set\n"
"    in the pending or priority registers, or it has some context\n"
"    enabled. The the following attributes are printed:\n"
"\n"
"      src     source number\n"
"      pend    pending bit\n"
"      prio    priority of the source\n"
"\n"
"    Additionally, for each enabled context of the source the\n"
"    following attributes are printed for that context:\n"
"\n"
"      ctx     context number\n"
"      thre    threshold value\n"
"      masked  the source is masked (prio <= thre)\n"
"\n"
"AUTHOR\n"
"    Rodrigo Arias Mallo <rodrigo.arias@bsc.es>\n"
"\n"
"SEE ALSO\n"
"    See https://github.com/riscv/riscv-plic-spec/\n"
"\n"
);
	exit(1);
}

static uint32_t
read_reg(void *base, size_t offset)
{
	volatile uint32_t *p = base + offset;
	return *p;
}

static void
write_reg(void *base, size_t offset, uint32_t value)
{
	volatile uint32_t *p = base + offset;
	*p = value;
}

static void
claim_interrupt(void *base, long ctx)
{
	size_t offset = 0x200004L + ctx * 0x1000;
	uint32_t value = read_reg(base, offset);
	printf("ctx=%ld claim=%u\n", ctx, value);
	write_reg(base, offset, value);
}

static void
dump_sources(void *base)
{
	for (long s = 0; s < nsources; s++) {
		int printed_source = 0;

		uint32_t *pending_reg  = base + 0x1000L + (s / 32L) * 4L;
		long shift = s % 32L;
		uint32_t pending = ((*pending_reg) >> shift) & 1;
		uint32_t *priority_reg = base + 0x0000L + (s * 4L);
		uint32_t priority = *priority_reg;

		const char *fmt =
			"src=%ld pend=%u prio=%u";

		if (pending || priority) {
			printf(fmt, s, pending, priority);
			printed_source = 1;
		}

		int first_context = 1;
		int enabled_contexts = 0;
		int unmasked = 0;
		for (long c = 0; c < ncontexts; c++) {
			uint32_t *enable_reg = base + 0x2000L + 0x80L * c + (s / 32L) * 4L;
			uint32_t enabled = ((*enable_reg) >> shift) & 1;
			uint32_t *threshold_reg = base + 0x200000L + (c * 0x1000L);
			uint32_t threshold = *threshold_reg;

			if (!enabled)
				continue;

			if (!printed_source) {
				printf(fmt, s, pending, priority);
				printed_source = 1;
			}


			int is_masked = priority <= threshold;

			if (!is_masked)
				unmasked++;

			const char *masked = is_masked ? "masked" : "unmasked";

			printf("\n    ctx=%ld thre=%u %s",
					c, threshold, masked);
			enabled_contexts++;
		}

		if (printed_source)
			printf("\n");
	}
}

int main(int argc, char *argv[])
{
	int opt;

	while ((opt = getopt(argc, argv, "a:hs:c:C:")) != -1) {
		switch (opt) {
			case 'a':
				plic_address_str = optarg;
				break;
			case 's':
				nsources = atol(optarg);
				break;
			case 'c':
				ncontexts = atol(optarg);
				break;
			case 'C':
				operation = CLAIM;
				claim_ctx = atol(optarg);
				break;
			case 'h':
			default: /* '?' */
				usage();
		}
	}

	unsigned long long plic_address = strtoull(plic_address_str, NULL, 16);

	printf("plictool "VERSION" addr=0x%08llx nsrc=%ld nctx=%ld\n",
			plic_address, nsources, ncontexts);

	//int fd = open("test.bin", O_RDWR | O_SYNC);
	int fd = open("/dev/mem", O_RDWR | O_SYNC);

	if (fd == -1) {
		perror("cannot open /dev/mem");
		exit(1);
	}

	size_t map_size = 0x4000000UL;
	void *map_base = mmap(0, map_size, PROT_READ | PROT_WRITE, MAP_SHARED,
			fd, plic_address);

	if (map_base == MAP_FAILED) {
		perror("mmap failed");
		if (errno == EPERM) {
			fprintf(stderr,	"Have you disabled 'CONFIG_STRICT_DEVMEM' and "
					"'CONFIG_IO_STRICT_DEVMEM' in the kernel config?\n"
					"Hint: zgrep STRICT_DEVMEM /proc/config.gz\n");
		}
		exit(1);
	}

	if (operation == CLAIM)
		claim_interrupt(map_base, claim_ctx);
	else if (operation == DUMP)
		dump_sources(map_base);

	munmap(map_base, map_size);

	close(fd);

	return 0;
}