| /* |
| * 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 <gpxe/timer2.h> |
| #include <gpxe/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 */ |
| } |
| } |