Linux-2.6.12-rc2
[linux-2.6.git] / arch / i386 / kernel / timers / common.c
1 /*
2  *      Common functions used across the timers go here
3  */
4
5 #include <linux/init.h>
6 #include <linux/timex.h>
7 #include <linux/errno.h>
8 #include <linux/jiffies.h>
9
10 #include <asm/io.h>
11 #include <asm/timer.h>
12 #include <asm/hpet.h>
13
14 #include "mach_timer.h"
15
16 /* ------ Calibrate the TSC -------
17  * Return 2^32 * (1 / (TSC clocks per usec)) for do_fast_gettimeoffset().
18  * Too much 64-bit arithmetic here to do this cleanly in C, and for
19  * accuracy's sake we want to keep the overhead on the CTC speaker (channel 2)
20  * output busy loop as low as possible. We avoid reading the CTC registers
21  * directly because of the awkward 8-bit access mechanism of the 82C54
22  * device.
23  */
24
25 #define CALIBRATE_TIME  (5 * 1000020/HZ)
26
27 unsigned long __init calibrate_tsc(void)
28 {
29         mach_prepare_counter();
30
31         {
32                 unsigned long startlow, starthigh;
33                 unsigned long endlow, endhigh;
34                 unsigned long count;
35
36                 rdtsc(startlow,starthigh);
37                 mach_countup(&count);
38                 rdtsc(endlow,endhigh);
39
40
41                 /* Error: ECTCNEVERSET */
42                 if (count <= 1)
43                         goto bad_ctc;
44
45                 /* 64-bit subtract - gcc just messes up with long longs */
46                 __asm__("subl %2,%0\n\t"
47                         "sbbl %3,%1"
48                         :"=a" (endlow), "=d" (endhigh)
49                         :"g" (startlow), "g" (starthigh),
50                          "0" (endlow), "1" (endhigh));
51
52                 /* Error: ECPUTOOFAST */
53                 if (endhigh)
54                         goto bad_ctc;
55
56                 /* Error: ECPUTOOSLOW */
57                 if (endlow <= CALIBRATE_TIME)
58                         goto bad_ctc;
59
60                 __asm__("divl %2"
61                         :"=a" (endlow), "=d" (endhigh)
62                         :"r" (endlow), "0" (0), "1" (CALIBRATE_TIME));
63
64                 return endlow;
65         }
66
67         /*
68          * The CTC wasn't reliable: we got a hit on the very first read,
69          * or the CPU was so fast/slow that the quotient wouldn't fit in
70          * 32 bits..
71          */
72 bad_ctc:
73         return 0;
74 }
75
76 #ifdef CONFIG_HPET_TIMER
77 /* ------ Calibrate the TSC using HPET -------
78  * Return 2^32 * (1 / (TSC clocks per usec)) for getting the CPU freq.
79  * Second output is parameter 1 (when non NULL)
80  * Set 2^32 * (1 / (tsc per HPET clk)) for delay_hpet().
81  * calibrate_tsc() calibrates the processor TSC by comparing
82  * it to the HPET timer of known frequency.
83  * Too much 64-bit arithmetic here to do this cleanly in C
84  */
85 #define CALIBRATE_CNT_HPET      (5 * hpet_tick)
86 #define CALIBRATE_TIME_HPET     (5 * KERNEL_TICK_USEC)
87
88 unsigned long __init calibrate_tsc_hpet(unsigned long *tsc_hpet_quotient_ptr)
89 {
90         unsigned long tsc_startlow, tsc_starthigh;
91         unsigned long tsc_endlow, tsc_endhigh;
92         unsigned long hpet_start, hpet_end;
93         unsigned long result, remain;
94
95         hpet_start = hpet_readl(HPET_COUNTER);
96         rdtsc(tsc_startlow, tsc_starthigh);
97         do {
98                 hpet_end = hpet_readl(HPET_COUNTER);
99         } while ((hpet_end - hpet_start) < CALIBRATE_CNT_HPET);
100         rdtsc(tsc_endlow, tsc_endhigh);
101
102         /* 64-bit subtract - gcc just messes up with long longs */
103         __asm__("subl %2,%0\n\t"
104                 "sbbl %3,%1"
105                 :"=a" (tsc_endlow), "=d" (tsc_endhigh)
106                 :"g" (tsc_startlow), "g" (tsc_starthigh),
107                  "0" (tsc_endlow), "1" (tsc_endhigh));
108
109         /* Error: ECPUTOOFAST */
110         if (tsc_endhigh)
111                 goto bad_calibration;
112
113         /* Error: ECPUTOOSLOW */
114         if (tsc_endlow <= CALIBRATE_TIME_HPET)
115                 goto bad_calibration;
116
117         ASM_DIV64_REG(result, remain, tsc_endlow, 0, CALIBRATE_TIME_HPET);
118         if (remain > (tsc_endlow >> 1))
119                 result++; /* rounding the result */
120
121         if (tsc_hpet_quotient_ptr) {
122                 unsigned long tsc_hpet_quotient;
123
124                 ASM_DIV64_REG(tsc_hpet_quotient, remain, tsc_endlow, 0,
125                         CALIBRATE_CNT_HPET);
126                 if (remain > (tsc_endlow >> 1))
127                         tsc_hpet_quotient++; /* rounding the result */
128                 *tsc_hpet_quotient_ptr = tsc_hpet_quotient;
129         }
130
131         return result;
132 bad_calibration:
133         /*
134          * the CPU was so fast/slow that the quotient wouldn't fit in
135          * 32 bits..
136          */
137         return 0;
138 }
139 #endif
140
141 /* calculate cpu_khz */
142 void __init init_cpu_khz(void)
143 {
144         if (cpu_has_tsc) {
145                 unsigned long tsc_quotient = calibrate_tsc();
146                 if (tsc_quotient) {
147                         /* report CPU clock rate in Hz.
148                          * The formula is (10^6 * 2^32) / (2^32 * 1 / (clocks/us)) =
149                          * clock/second. Our precision is about 100 ppm.
150                          */
151                         {       unsigned long eax=0, edx=1000;
152                                 __asm__("divl %2"
153                                 :"=a" (cpu_khz), "=d" (edx)
154                                 :"r" (tsc_quotient),
155                                 "0" (eax), "1" (edx));
156                                 printk("Detected %lu.%03lu MHz processor.\n", cpu_khz / 1000, cpu_khz % 1000);
157                         }
158                 }
159         }
160 }