1 /*
2  * test module to check whether the TSC-based delay routine continues
3  * to work properly after cpufreq transitions. Needs ACPI to work
4  * properly.
5  *
6  * Based partly on the Power Management Timer (PMTMR) code to be found
7  * in arch/i386/kernel/timers/timer_pm.c on recent 2.6. kernels, especially
8  * code written by John Stultz. The read_pmtmr function was copied verbatim
9  * from that file.
10  *
11  * (C) 2004 Dominik Brodowski
12  *
13  * To use:
14  * 1.) pass clock=tsc to the kernel on your bootloader
15  * 2.) modprobe this module (it'll fail)
16  * 3.) change CPU frequency
17  * 4.) modprobe this module again
18  * 5.) if the third value, "diff_pmtmr", changes between 2. and 4., the
19  *     TSC-based delay routine on the Linux kernel does not correctly
20  *     handle the cpufreq transition. Please report this to
21  *     cpufreq@vger.kernel.org
22  */
23 
24 #include <linux/kernel.h>
25 #include <linux/module.h>
26 #include <linux/init.h>
27 #include <linux/delay.h>
28 
29 #include <asm/io.h>
30 
31 #include <acpi/acpi_bus.h>
32 #include <acpi/acpi_drivers.h>
33 
34 static int pm_tmr_ioport = 0;
35 
36 /*helper function to safely read acpi pm timesource*/
37 static u32 read_pmtmr(void)
38 {
39 	u32 v1=0,v2=0,v3=0;
40 	/* It has been reported that because of various broken
41 	 * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM time
42 	 * source is not latched, so you must read it multiple
43 	 * times to insure a safe value is read.
44 	 */
45 	do {
46 		v1 = inl(pm_tmr_ioport);
47 		v2 = inl(pm_tmr_ioport);
48 		v3 = inl(pm_tmr_ioport);
49 	} while ((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
50 		 || (v3 > v1 && v3 < v2));
51 
52 	/* mask the output to 24 bits */
53 	return (v2 & 0xFFFFFF);
54 }
55 
56 static int __init cpufreq_test_tsc(void)
57 {
58 	u32 now, then, diff;
59 	u64 now_tsc, then_tsc, diff_tsc;
60 	int i;
61 
62 	/* the following code snipped is copied from arch/x86/kernel/acpi/boot.c
63 	   of Linux v2.6.25. */
64 
65 	/* detect the location of the ACPI PM Timer */
66 	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID) {
67 		/* FADT rev. 2 */
68 		if (acpi_gbl_FADT.xpm_timer_block.space_id !=
69 		    ACPI_ADR_SPACE_SYSTEM_IO)
70 			return 0;
71 
72 		pm_tmr_ioport = acpi_gbl_FADT.xpm_timer_block.address;
73 		/*
74 		 * "X" fields are optional extensions to the original V1.0
75 		 * fields, so we must selectively expand V1.0 fields if the
76 		 * corresponding X field is zero.
77 	 	 */
78 		if (!pm_tmr_ioport)
79 			pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block;
80 	} else {
81 		/* FADT rev. 1 */
82 		pm_tmr_ioport = acpi_gbl_FADT.pm_timer_block;
83 	}
84 
85 	printk(KERN_DEBUG "start--> \n");
86 	then = read_pmtmr();
87         rdtscll(then_tsc);
88 	for (i=0;i<20;i++) {
89 		mdelay(100);
90 		now = read_pmtmr();
91 		rdtscll(now_tsc);
92 		diff = (now - then) & 0xFFFFFF;
93 		diff_tsc = now_tsc - then_tsc;
94 		printk(KERN_DEBUG "t1: %08u t2: %08u diff_pmtmr: %08u diff_tsc: %016llu\n", then, now, diff, diff_tsc);
95 		then = now;
96 		then_tsc = now_tsc;
97 	}
98 	printk(KERN_DEBUG "<-- end \n");
99 	return -ENODEV;
100 }
101 
102 static void __exit cpufreq_none(void)
103 {
104 	return;
105 }
106 
107 module_init(cpufreq_test_tsc)
108 module_exit(cpufreq_none)
109 
110 
111 MODULE_AUTHOR("Dominik Brodowski");
112 MODULE_DESCRIPTION("Verify the TSC cpufreq notifier working correctly -- needs ACPI-enabled system");
113 MODULE_LICENSE ("GPL");
114