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/* * include/asm-i386/mach-default/mach_timer.h * * Machine specific calibrate_tsc() for generic. * Split out from timer_tsc.c by Osamu Tomita <tomita@cinet.co.jp> */ /* ------ Calibrate the TSC ------- * Return 2^32 * (1 / (TSC clocks per usec)) for do_fast_gettimeoffset(). * Too much 64-bit arithmetic here to do this cleanly in C, and for * accuracy's sake we want to keep the overhead on the CTC speaker (channel 2) * output busy loop as low as possible. We avoid reading the CTC registers * directly because of the awkward 8-bit access mechanism of the 82C54 * device. */ #ifndef _MACH_TIMER_H #define _MACH_TIMER_H #define CALIBRATE_LATCH (5 * LATCH) static inline void mach_prepare_counter(void) { /* Set the Gate high, disable speaker */ outb((inb(0x61) & ~0x02) | 0x01, 0x61); /* * Now let's take care of CTC channel 2 * * Set the Gate high, program CTC channel 2 for mode 0, * (interrupt on terminal count mode), binary count, * load 5 * LATCH count, (LSB and MSB) to begin countdown. * * Some devices need a delay here. */ outb(0xb0, 0x43); /* binary, mode 0, LSB/MSB, Ch 2 */ outb_p(CALIBRATE_LATCH & 0xff, 0x42); /* LSB of count */ outb_p(CALIBRATE_LATCH >> 8, 0x42); /* MSB of count */ } static inline void mach_countup(unsigned long *count_p) { unsigned long count = 0; do { count++; } while ((inb_p(0x61) & 0x20) == 0); *count_p = count; } #endif /* !_MACH_TIMER_H */