1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Real Time Clock Periodic Interrupt test program
4  *
5  * Since commit 6610e0893b8bc ("RTC: Rework RTC code to use timerqueue for
6  * events"), PIE are completely handled using hrtimers, without actually using
7  * any underlying hardware RTC.
8  *
9  */
10 
11 #include <stdio.h>
12 #include <linux/rtc.h>
13 #include <sys/ioctl.h>
14 #include <sys/time.h>
15 #include <sys/types.h>
16 #include <fcntl.h>
17 #include <unistd.h>
18 #include <stdlib.h>
19 #include <errno.h>
20 
21 /*
22  * This expects the new RTC class driver framework, working with
23  * clocks that will often not be clones of what the PC-AT had.
24  * Use the command line to specify another RTC if you need one.
25  */
26 static const char default_rtc[] = "/dev/rtc0";
27 
28 int main(int argc, char **argv)
29 {
30 	int i, fd, retval, irqcount = 0;
31 	unsigned long tmp, data, old_pie_rate;
32 	const char *rtc = default_rtc;
33 	struct timeval start, end, diff;
34 
35 	switch (argc) {
36 	case 2:
37 		rtc = argv[1];
38 		/* FALLTHROUGH */
39 	case 1:
40 		break;
41 	default:
42 		fprintf(stderr, "usage:  rtctest [rtcdev] [d]\n");
43 		return 1;
44 	}
45 
46 	fd = open(rtc, O_RDONLY);
47 
48 	if (fd ==  -1) {
49 		perror(rtc);
50 		exit(errno);
51 	}
52 
53 	/* Read periodic IRQ rate */
54 	retval = ioctl(fd, RTC_IRQP_READ, &old_pie_rate);
55 	if (retval == -1) {
56 		/* not all RTCs support periodic IRQs */
57 		if (errno == EINVAL) {
58 			fprintf(stderr, "\nNo periodic IRQ support\n");
59 			goto done;
60 		}
61 		perror("RTC_IRQP_READ ioctl");
62 		exit(errno);
63 	}
64 	fprintf(stderr, "\nPeriodic IRQ rate is %ldHz.\n", old_pie_rate);
65 
66 	fprintf(stderr, "Counting 20 interrupts at:");
67 	fflush(stderr);
68 
69 	/* The frequencies 128Hz, 256Hz, ... 8192Hz are only allowed for root. */
70 	for (tmp=2; tmp<=64; tmp*=2) {
71 
72 		retval = ioctl(fd, RTC_IRQP_SET, tmp);
73 		if (retval == -1) {
74 			/* not all RTCs can change their periodic IRQ rate */
75 			if (errno == EINVAL) {
76 				fprintf(stderr,
77 					"\n...Periodic IRQ rate is fixed\n");
78 				goto done;
79 			}
80 			perror("RTC_IRQP_SET ioctl");
81 			exit(errno);
82 		}
83 
84 		fprintf(stderr, "\n%ldHz:\t", tmp);
85 		fflush(stderr);
86 
87 		/* Enable periodic interrupts */
88 		retval = ioctl(fd, RTC_PIE_ON, 0);
89 		if (retval == -1) {
90 			perror("RTC_PIE_ON ioctl");
91 			exit(errno);
92 		}
93 
94 		for (i=1; i<21; i++) {
95 			gettimeofday(&start, NULL);
96 			/* This blocks */
97 			retval = read(fd, &data, sizeof(unsigned long));
98 			if (retval == -1) {
99 				perror("read");
100 				exit(errno);
101 			}
102 			gettimeofday(&end, NULL);
103 			timersub(&end, &start, &diff);
104 			if (diff.tv_sec > 0 ||
105 			    diff.tv_usec > ((1000000L / tmp) * 1.10)) {
106 				fprintf(stderr, "\nPIE delta error: %ld.%06ld should be close to 0.%06ld\n",
107 				       diff.tv_sec, diff.tv_usec,
108 				       (1000000L / tmp));
109 				fflush(stdout);
110 				exit(-1);
111 			}
112 
113 			fprintf(stderr, " %d",i);
114 			fflush(stderr);
115 			irqcount++;
116 		}
117 
118 		/* Disable periodic interrupts */
119 		retval = ioctl(fd, RTC_PIE_OFF, 0);
120 		if (retval == -1) {
121 			perror("RTC_PIE_OFF ioctl");
122 			exit(errno);
123 		}
124 	}
125 
126 done:
127 	ioctl(fd, RTC_IRQP_SET, old_pie_rate);
128 
129 	fprintf(stderr, "\n\n\t\t\t *** Test complete ***\n");
130 
131 	close(fd);
132 
133 	return 0;
134 }
135