/* Copyright (c) 2015, Linaro Limited
 * All rights reserved.
 *
 * SPDX-License-Identifier:	BSD-3-Clause
 */

/*
 * Program to read perf counter on ARMv8 from userspace using mmap way
 */
#define _GNU_SOURCE
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/syscall.h>
#include <linux/perf_event.h>
#include <linux/types.h>
#include <sys/mman.h>
#include <errno.h>
#include <string.h>
#include <getopt.h>
#include <math.h>
#include <signal.h>
#include <fcntl.h>

#define barrier()	asm volatile("dmb ish" : : : "memory")
#define isb()		asm volatile("isb" : : : "memory")
#define ARMV8_PMCNTENSET_EL0_ENABLE (1<<31) /**< Enable Perf count reg */
static int fddev = -1;
static unsigned long page_size;
static int overflow;

static void sigio_handler(int signo, siginfo_t *info, void *uc)
{
	overflow = overflow + 1;
}

static int counter_init(unsigned int counter,long unsigned int sample)
{
	static struct perf_event_attr attr;
	static struct sigaction sigio;
	attr.type = PERF_TYPE_HARDWARE;
	if (counter < 0 || counter > PERF_COUNT_HW_MAX)
		return -1;

	/* setup SIGIO signal handler */
	memset(&sigio, 0, sizeof(struct sigaction));
	sigio.sa_sigaction = (void *)sigio_handler;
	sigio.sa_flags = SA_SIGINFO;

	if (sigaction(SIGIO, &sigio, NULL) == -1) {
		printf("Error: SIGIO signal handler %s\n",strerror(errno));
	}
	attr.sample_period = sample;
	memset(&attr,0,sizeof(struct perf_event_attr));
	attr.size = sizeof(struct perf_event_attr);
	attr.sample_type = PERF_SAMPLE_IP;
	attr.wakeup_events = 1;
	attr.config = counter;
	attr.mmap = 1;
	attr.watermark = 0;
	attr.disabled = 1;
	fddev = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0);
	if (fddev == -1) {
		fprintf(stderr,
			"Error opening perf_event_open for counter %llx\n",
			attr.config);
		return -1;
	}

	fcntl(fddev, F_SETFL, O_RDWR|O_NONBLOCK|O_ASYNC);
	fcntl(fddev, F_SETSIG, SIGIO);
	fcntl(fddev, F_SETOWN, getpid());
	return 0;
}

static unsigned long rdpmc(unsigned int counter)
{
	unsigned long int ret;
	if (counter == PERF_COUNT_HW_CPU_CYCLES)
		asm volatile("mrs %0, pmccntr_el0" : "=r" (ret));
	else {
		asm volatile("msr pmselr_el0, %0" : : "r" ((counter-1)));
		asm volatile("mrs %0, pmxevcntr_el0" : "=r" (ret));
	}

	isb();
	return ret;
}

static unsigned long mmap_read_self(void *addr)
{
	struct perf_event_mmap_page *pc = addr;
	unsigned int seq, idx;
	unsigned long  count;
	do {
		count = 0;
		seq = pc->lock;
		barrier();
		idx = pc->index;
		count = pc->offset;
		if (idx)
			count += rdpmc(idx - 1);
		barrier();
	} while (pc->lock != seq);

	return count;
}

/* loop body to keep things interested. Make sure it gets inlined. */
static inline int
loop(int* __restrict__ a, int* __restrict__ b, int n)
{
	unsigned sum = 0;
	int i = 0;
	for (i = 0; i < n; ++i)
		if (a[i] > b[i])
			sum += a[i] + 5;

	return sum;
}

void print_usage(char *argv)
{
	printf("Usage: %s -c perf_hw_counter -n length\n"
	"%s - read perf hardware counters from userspace\n\n"
	"-c\t perf_hw_counter is enum value of hw counter for platform\n"
	"Refer to 'enum perf_hw_id'[file <linux/perf_event.h>] for hw\n"
	"counter enum value in range of 0 to PERF_COUNT_HW_MAX\n"
	"-n\t Length size array will implement busyloop\n"
	"-s\t Sample period [> 1000000 samples]\n"
	"e.g.\n"
	"\t%s -c 0 -n 64 -s 1000000\n", argv, argv, argv);
}

int main(int ac, char *argv[])
{
	int option = 0;
	int *a  = NULL;
	int *b  = NULL;
	int len = -1, cnt = -1;
	int i, pre_loop_res, post_loop_res, sum = 0;
	void *addr; /* mmaped address */
	unsigned long start_count, stop_count, s_period=1000000;

	while ((option = getopt(ac, argv, "c:n:s:")) != -1) {
		switch (option) {
		case 'c':
			cnt = atoi(optarg);
			break;
		case 'n':
			len = atoi(optarg);
			break;
		case 's':
			s_period = atoi(optarg);
			break;
		default:
			print_usage(argv[0]);
			exit(EXIT_FAILURE);
		}
	}

	if (len == -1 || cnt == -1) {
		print_usage(argv[0]);
		exit(EXIT_FAILURE);
	}

	if (counter_init(cnt, s_period) < 0) {
		printf("Error: Counter Invalid\n");
		print_usage(argv[0]);
		exit(EXIT_FAILURE);
	}

	a = malloc(len*sizeof(*a));
	b = malloc(len*sizeof(*b));
	ioctl(fddev, PERF_EVENT_IOC_RESET, 0);
	ioctl(fddev, PERF_EVENT_IOC_ENABLE, 0);

	for (i = 0; i < len; ++i) {
		a[i] = i+128;
		b[i] = i+64;
	}

	page_size = sysconf(_SC_PAGESIZE);
	/*Allocate memory for the page size */
	addr = mmap(NULL, page_size, PROT_READ, MAP_SHARED, fddev, 0);

	if (addr == (void *)(-1)) {
		printf("Error: mmap() syscall returned with (%s)\n",
		       strerror(errno));
		print_usage(argv[0]);
		exit(EXIT_FAILURE);
	}

	i = 0;
	start_count = stop_count = 0;
	ioctl(fddev, PERF_EVENT_IOC_RESET, 0);
	/* --------------------Critical section-------------- */
	start_count = mmap_read_self(addr);
	for (i = 0; i < 1000; i++) {
		sum = loop(a, b, len);
		mmap_read_self(addr);
	}

	stop_count = mmap_read_self(addr);
	/* --------------------End Critical section-------------- */
	pre_loop_res = abs(stop_count-start_count)/1000;
	printf("\nsum=%d Avg count [ Loop + Read ] = %ld\n", sum,
		pre_loop_res);
	start_count = stop_count = 0;
	/* --------------------Critical section-------------- */
	start_count = mmap_read_self(addr);
	for (i = 0; i < 1000; i++)
		sum = loop(a, b, len);

	stop_count = mmap_read_self(addr);
	ioctl(fddev, PERF_EVENT_IOC_DISABLE, 0);
	/* --------------------End Critical section-------------- */
	post_loop_res = abs(stop_count-start_count)/1000;
	printf("sum=%d Avg count [ Loop        ] = %ld\n", sum,
	       post_loop_res);
	printf("\n--------------------------------------------------------\n");
	printf("\tDelay[cpucycles]=%d\n", abs(post_loop_res - pre_loop_res));
	printf("\tNumber of time overflow happens=%d\n", overflow);
	printf("\n--------------------------------------------------------\n");
	munmap(addr, page_size);
	free(a);
	free(b);
	close(fddev);
	return 0;
}