1/* 2 * include/asm-i386/mach-default/mach_timer.h 3 * 4 * Machine specific calibrate_tsc() for generic. 5 * Split out from timer_tsc.c by Osamu Tomita <tomita@cinet.co.jp> 6 */ 7/* ------ Calibrate the TSC ------- 8 * Return 2^32 * (1 / (TSC clocks per usec)) for do_fast_gettimeoffset(). 9 * Too much 64-bit arithmetic here to do this cleanly in C, and for 10 * accuracy's sake we want to keep the overhead on the CTC speaker (channel 2) 11 * output busy loop as low as possible. We avoid reading the CTC registers 12 * directly because of the awkward 8-bit access mechanism of the 82C54 13 * device. 14 */ 15#ifndef _MACH_TIMER_H 16#define _MACH_TIMER_H 17 18#define CALIBRATE_TIME_MSEC 30 /* 30 msecs */ 19#define CALIBRATE_LATCH \ 20 ((CLOCK_TICK_RATE * CALIBRATE_TIME_MSEC + 1000/2)/1000) 21 22static inline void mach_prepare_counter(void) 23{ 24 /* Set the Gate high, disable speaker */ 25 outb((inb(0x61) & ~0x02) | 0x01, 0x61); 26 27 /* 28 * Now let's take care of CTC channel 2 29 * 30 * Set the Gate high, program CTC channel 2 for mode 0, 31 * (interrupt on terminal count mode), binary count, 32 * load 5 * LATCH count, (LSB and MSB) to begin countdown. 33 * 34 * Some devices need a delay here. 35 */ 36 outb(0xb0, 0x43); /* binary, mode 0, LSB/MSB, Ch 2 */ 37 outb_p(CALIBRATE_LATCH & 0xff, 0x42); /* LSB of count */ 38 outb_p(CALIBRATE_LATCH >> 8, 0x42); /* MSB of count */ 39} 40 41static inline void mach_countup(unsigned long *count_p) 42{ 43 unsigned long count = 0; 44 do { 45 count++; 46 } while ((inb_p(0x61) & 0x20) == 0); 47 *count_p = count; 48} 49 50#endif /* !_MACH_TIMER_H */ 51