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- /*
- * arch/i386/core/i386_timer.c
- *
- * Use the "System Timer 2" to implement the udelay callback in
- * the BIOS timer driver. Also used to calibrate the clock rate
- * in the RTDSC timer driver.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2, or (at
- * your option) any later version.
- */
-
- FILE_LICENCE ( GPL2_OR_LATER );
-
- #include <stddef.h>
- #include <ipxe/timer2.h>
- #include <ipxe/io.h>
-
- /* Timers tick over at this rate */
- #define TIMER2_TICKS_PER_SEC 1193180U
-
- /* Parallel Peripheral Controller Port B */
- #define PPC_PORTB 0x61
-
- /* Meaning of the port bits */
- #define PPCB_T2OUT 0x20 /* Bit 5 */
- #define PPCB_SPKR 0x02 /* Bit 1 */
- #define PPCB_T2GATE 0x01 /* Bit 0 */
-
- /* Ports for the 8254 timer chip */
- #define TIMER2_PORT 0x42
- #define TIMER_MODE_PORT 0x43
-
- /* Meaning of the mode bits */
- #define TIMER0_SEL 0x00
- #define TIMER1_SEL 0x40
- #define TIMER2_SEL 0x80
- #define READBACK_SEL 0xC0
-
- #define LATCH_COUNT 0x00
- #define LOBYTE_ACCESS 0x10
- #define HIBYTE_ACCESS 0x20
- #define WORD_ACCESS 0x30
-
- #define MODE0 0x00
- #define MODE1 0x02
- #define MODE2 0x04
- #define MODE3 0x06
- #define MODE4 0x08
- #define MODE5 0x0A
-
- #define BINARY_COUNT 0x00
- #define BCD_COUNT 0x01
-
- static void load_timer2 ( unsigned int ticks ) {
- /*
- * Now let's take care of PPC channel 2
- *
- * Set the Gate high, program PPC channel 2 for mode 0,
- * (interrupt on terminal count mode), binary count,
- * load 5 * LATCH count, (LSB and MSB) to begin countdown.
- *
- * Note some implementations have a bug where the high bits byte
- * of channel 2 is ignored.
- */
- /* Set up the timer gate, turn off the speaker */
- /* Set the Gate high, disable speaker */
- outb((inb(PPC_PORTB) & ~PPCB_SPKR) | PPCB_T2GATE, PPC_PORTB);
- /* binary, mode 0, LSB/MSB, Ch 2 */
- outb(TIMER2_SEL|WORD_ACCESS|MODE0|BINARY_COUNT, TIMER_MODE_PORT);
- /* LSB of ticks */
- outb(ticks & 0xFF, TIMER2_PORT);
- /* MSB of ticks */
- outb(ticks >> 8, TIMER2_PORT);
- }
-
- static int timer2_running ( void ) {
- return ((inb(PPC_PORTB) & PPCB_T2OUT) == 0);
- }
-
- void timer2_udelay ( unsigned long usecs ) {
- load_timer2 ( ( usecs * TIMER2_TICKS_PER_SEC ) / ( 1000 * 1000 ) );
- while (timer2_running()) {
- /* Do nothing */
- }
- }
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