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>
9 #include <linux/module.h>
12 #include <asm/timer.h>
15 #include "mach_timer.h"
17 /* ------ Calibrate the TSC -------
18 * Return 2^32 * (1 / (TSC clocks per usec)) for do_fast_gettimeoffset().
19 * Too much 64-bit arithmetic here to do this cleanly in C, and for
20 * accuracy's sake we want to keep the overhead on the CTC speaker (channel 2)
21 * output busy loop as low as possible. We avoid reading the CTC registers
22 * directly because of the awkward 8-bit access mechanism of the 82C54
26 #define CALIBRATE_TIME (5 * 1000020/HZ)
28 unsigned long calibrate_tsc(void)
30 mach_prepare_counter();
33 unsigned long startlow
, starthigh
;
34 unsigned long endlow
, endhigh
;
37 rdtsc(startlow
,starthigh
);
39 rdtsc(endlow
,endhigh
);
42 /* Error: ECTCNEVERSET */
46 /* 64-bit subtract - gcc just messes up with long longs */
47 __asm__("subl %2,%0\n\t"
49 :"=a" (endlow
), "=d" (endhigh
)
50 :"g" (startlow
), "g" (starthigh
),
51 "0" (endlow
), "1" (endhigh
));
53 /* Error: ECPUTOOFAST */
57 /* Error: ECPUTOOSLOW */
58 if (endlow
<= CALIBRATE_TIME
)
62 :"=a" (endlow
), "=d" (endhigh
)
63 :"r" (endlow
), "0" (0), "1" (CALIBRATE_TIME
));
69 * The CTC wasn't reliable: we got a hit on the very first read,
70 * or the CPU was so fast/slow that the quotient wouldn't fit in
77 #ifdef CONFIG_HPET_TIMER
78 /* ------ Calibrate the TSC using HPET -------
79 * Return 2^32 * (1 / (TSC clocks per usec)) for getting the CPU freq.
80 * Second output is parameter 1 (when non NULL)
81 * Set 2^32 * (1 / (tsc per HPET clk)) for delay_hpet().
82 * calibrate_tsc() calibrates the processor TSC by comparing
83 * it to the HPET timer of known frequency.
84 * Too much 64-bit arithmetic here to do this cleanly in C
86 #define CALIBRATE_CNT_HPET (5 * hpet_tick)
87 #define CALIBRATE_TIME_HPET (5 * KERNEL_TICK_USEC)
89 unsigned long __devinit
calibrate_tsc_hpet(unsigned long *tsc_hpet_quotient_ptr
)
91 unsigned long tsc_startlow
, tsc_starthigh
;
92 unsigned long tsc_endlow
, tsc_endhigh
;
93 unsigned long hpet_start
, hpet_end
;
94 unsigned long result
, remain
;
96 hpet_start
= hpet_readl(HPET_COUNTER
);
97 rdtsc(tsc_startlow
, tsc_starthigh
);
99 hpet_end
= hpet_readl(HPET_COUNTER
);
100 } while ((hpet_end
- hpet_start
) < CALIBRATE_CNT_HPET
);
101 rdtsc(tsc_endlow
, tsc_endhigh
);
103 /* 64-bit subtract - gcc just messes up with long longs */
104 __asm__("subl %2,%0\n\t"
106 :"=a" (tsc_endlow
), "=d" (tsc_endhigh
)
107 :"g" (tsc_startlow
), "g" (tsc_starthigh
),
108 "0" (tsc_endlow
), "1" (tsc_endhigh
));
110 /* Error: ECPUTOOFAST */
112 goto bad_calibration
;
114 /* Error: ECPUTOOSLOW */
115 if (tsc_endlow
<= CALIBRATE_TIME_HPET
)
116 goto bad_calibration
;
118 ASM_DIV64_REG(result
, remain
, tsc_endlow
, 0, CALIBRATE_TIME_HPET
);
119 if (remain
> (tsc_endlow
>> 1))
120 result
++; /* rounding the result */
122 if (tsc_hpet_quotient_ptr
) {
123 unsigned long tsc_hpet_quotient
;
125 ASM_DIV64_REG(tsc_hpet_quotient
, remain
, tsc_endlow
, 0,
127 if (remain
> (tsc_endlow
>> 1))
128 tsc_hpet_quotient
++; /* rounding the result */
129 *tsc_hpet_quotient_ptr
= tsc_hpet_quotient
;
135 * the CPU was so fast/slow that the quotient wouldn't fit in
143 unsigned long read_timer_tsc(void)
145 unsigned long retval
;
151 /* calculate cpu_khz */
152 void init_cpu_khz(void)
155 unsigned long tsc_quotient
= calibrate_tsc();
157 /* report CPU clock rate in Hz.
158 * The formula is (10^6 * 2^32) / (2^32 * 1 / (clocks/us)) =
159 * clock/second. Our precision is about 100 ppm.
161 { unsigned long eax
=0, edx
=1000;
163 :"=a" (cpu_khz
), "=d" (edx
)
165 "0" (eax
), "1" (edx
));
166 printk("Detected %u.%03u MHz processor.\n",
167 cpu_khz
/ 1000, cpu_khz
% 1000);