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/* Defines for 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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/* Ports for the 8254 timer chip */
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#define TIMER2_PORT 0x42
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#define TIMER_MODE_PORT 0x43
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/* Meaning of the mode bits */
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#define TIMER0_SEL 0x00
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#define TIMER1_SEL 0x40
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#define TIMER2_SEL 0x80
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#define READBACK_SEL 0xC0
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#define LATCH_COUNT 0x00
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#define LOBYTE_ACCESS 0x10
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#define HIBYTE_ACCESS 0x20
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#define WORD_ACCESS 0x30
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#define BINARY_COUNT 0x00
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#define BCD_COUNT 0x01
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/* Timers tick over at this rate */
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#define TICKS_PER_MS 1193
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/* Parallel Peripheral Controller Port B */
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#define PPC_PORTB 0x61
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/* Meaning of the port bits */
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#define PPCB_T2OUT 0x20 /* Bit 5 */
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#define PPCB_SPKR 0x02 /* Bit 1 */
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#define PPCB_T2GATE 0x01 /* Bit 0 */
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/* Ticks must be between 0 and 65535 (0 == 65536)
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because it is a 16 bit counter */
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extern void load_timer2(unsigned int ticks);
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extern inline int timer2_running(void)
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return ((inb(PPC_PORTB) & PPCB_T2OUT) == 0);
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extern inline void waiton_timer2(unsigned int ticks)
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while ((inb(PPC_PORTB) & PPCB_T2OUT) == 0)