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/* A couple of routines to implement a low-overhead timer for drivers */
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2, or (at
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* your option) any later version.
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#include "etherboot.h"
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void load_timer2(unsigned int ticks)
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/* Set up the timer gate, turn off the speaker */
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outb((inb(PPC_PORTB) & ~PPCB_SPKR) | PPCB_T2GATE, PPC_PORTB);
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outb(TIMER2_SEL|WORD_ACCESS|MODE0|BINARY_COUNT, TIMER_MODE_PORT);
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outb(ticks & 0xFF, TIMER2_PORT);
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outb(ticks >> 8, TIMER2_PORT);
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#if defined(CONFIG_TSC_CURRTICKS)
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#define rdtsc(low,high) \
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__asm__ __volatile__("rdtsc" : "=a" (low), "=d" (high))
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#define rdtscll(val) \
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__asm__ __volatile__ ("rdtsc" : "=A" (val))
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#define HZ TICKS_PER_SEC
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#define CLOCK_TICK_RATE 1193180U /* Underlying HZ */
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/* LATCH is used in the interval timer and ftape setup. */
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#define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */
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/* ------ Calibrate the TSC -------
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* Return 2^32 * (1 / (TSC clocks per usec)) for do_fast_gettimeoffset().
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* Too much 64-bit arithmetic here to do this cleanly in C, and for
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* accuracy's sake we want to keep the overhead on the CTC speaker (channel 2)
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* output busy loop as low as possible. We avoid reading the CTC registers
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* directly because of the awkward 8-bit access mechanism of the 82C54
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#define CALIBRATE_LATCH (5 * LATCH)
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static unsigned long long calibrate_tsc(void)
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/* Set the Gate high, disable speaker */
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outb((inb(0x61) & ~0x02) | 0x01, 0x61);
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* Now let's take care of CTC channel 2
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* Set the Gate high, program CTC channel 2 for mode 0,
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* (interrupt on terminal count mode), binary count,
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* load 5 * LATCH count, (LSB and MSB) to begin countdown.
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outb(0xb0, 0x43); /* binary, mode 0, LSB/MSB, Ch 2 */
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outb(CALIBRATE_LATCH & 0xff, 0x42); /* LSB of count */
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outb(CALIBRATE_LATCH >> 8, 0x42); /* MSB of count */
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unsigned long startlow, starthigh;
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unsigned long endlow, endhigh;
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rdtsc(startlow,starthigh);
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} while ((inb(0x61) & 0x20) == 0);
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rdtsc(endlow,endhigh);
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/* Error: ECTCNEVERSET */
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/* 64-bit subtract - gcc just messes up with long longs */
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__asm__("subl %2,%0\n\t"
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:"=a" (endlow), "=d" (endhigh)
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:"g" (startlow), "g" (starthigh),
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"0" (endlow), "1" (endhigh));
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/* Error: ECPUTOOFAST */
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* The CTC wasn't reliable: we got a hit on the very first read,
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* or the CPU was so fast/slow that the quotient wouldn't fit in
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unsigned long currticks(void)
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static unsigned long clocks_per_tick;
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unsigned long clocks_high, clocks_low;
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unsigned long currticks;
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if (!clocks_per_tick) {
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clocks_per_tick = calibrate_tsc();
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printf("clocks_per_tick = %d\n", clocks_per_tick);
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/* Read the Time Stamp Counter */
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rdtsc(clocks_low, clocks_high);
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/* currticks = clocks / clocks_per_tick; */
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:"r" (clocks_per_tick), "0" (clocks_low), "d" (clocks_high));
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#endif /* RTC_CURRTICKS */