2 * Common functions used across the timers go here
5 #include <linux/init.h>
6 #include <linux/timex.h>
7 #include <linux/errno.h>
8 #include <linux/jiffies.h>
11 #include <asm/timer.h>
14 #include "mach_timer.h"
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
25 #define CALIBRATE_TIME (5 * 1000020/HZ)
27 unsigned long __init calibrate_tsc(void)
29 mach_prepare_counter();
32 unsigned long startlow, starthigh;
33 unsigned long endlow, endhigh;
36 rdtsc(startlow,starthigh);
38 rdtsc(endlow,endhigh);
41 /* Error: ECTCNEVERSET */
45 /* 64-bit subtract - gcc just messes up with long longs */
46 __asm__("subl %2,%0\n\t"
48 :"=a" (endlow), "=d" (endhigh)
49 :"g" (startlow), "g" (starthigh),
50 "0" (endlow), "1" (endhigh));
52 /* Error: ECPUTOOFAST */
56 /* Error: ECPUTOOSLOW */
57 if (endlow <= CALIBRATE_TIME)
61 :"=a" (endlow), "=d" (endhigh)
62 :"r" (endlow), "0" (0), "1" (CALIBRATE_TIME));
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
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
85 #define CALIBRATE_CNT_HPET (5 * hpet_tick)
86 #define CALIBRATE_TIME_HPET (5 * KERNEL_TICK_USEC)
88 unsigned long __init calibrate_tsc_hpet(unsigned long *tsc_hpet_quotient_ptr)
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;
95 hpet_start = hpet_readl(HPET_COUNTER);
96 rdtsc(tsc_startlow, tsc_starthigh);
98 hpet_end = hpet_readl(HPET_COUNTER);
99 } while ((hpet_end - hpet_start) < CALIBRATE_CNT_HPET);
100 rdtsc(tsc_endlow, tsc_endhigh);
102 /* 64-bit subtract - gcc just messes up with long longs */
103 __asm__("subl %2,%0\n\t"
105 :"=a" (tsc_endlow), "=d" (tsc_endhigh)
106 :"g" (tsc_startlow), "g" (tsc_starthigh),
107 "0" (tsc_endlow), "1" (tsc_endhigh));
109 /* Error: ECPUTOOFAST */
111 goto bad_calibration;
113 /* Error: ECPUTOOSLOW */
114 if (tsc_endlow <= CALIBRATE_TIME_HPET)
115 goto bad_calibration;
117 ASM_DIV64_REG(result, remain, tsc_endlow, 0, CALIBRATE_TIME_HPET);
118 if (remain > (tsc_endlow >> 1))
119 result++; /* rounding the result */
121 if (tsc_hpet_quotient_ptr) {
122 unsigned long tsc_hpet_quotient;
124 ASM_DIV64_REG(tsc_hpet_quotient, remain, tsc_endlow, 0,
126 if (remain > (tsc_endlow >> 1))
127 tsc_hpet_quotient++; /* rounding the result */
128 *tsc_hpet_quotient_ptr = tsc_hpet_quotient;
134 * the CPU was so fast/slow that the quotient wouldn't fit in
141 /* calculate cpu_khz */
142 void __init init_cpu_khz(void)
145 unsigned long tsc_quotient = calibrate_tsc();
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.
151 { unsigned long eax=0, edx=1000;
153 :"=a" (cpu_khz), "=d" (edx)
155 "0" (eax), "1" (edx));
156 printk("Detected %lu.%03lu MHz processor.\n", cpu_khz / 1000, cpu_khz % 1000);