1/* 2 * Copyright 2014, General Dynamics C4 Systems 3 * 4 * SPDX-License-Identifier: GPL-2.0-only 5 */ 6 7#include <linker.h> 8#include <machine/io.h> 9#include <plat/machine/pit.h> 10 11/* PIT (i8253) registers */ 12#define PIT_MODE 0x43 13#define PIT_CH0 0x40 14 15/* Count frequency in Hz */ 16#define PIT_HZ 1193182 17 18BOOT_CODE void pit_init(void) 19{ 20 uint16_t divisor = (PIT_HZ * PIT_WRAPAROUND_MS) / 1000; 21 22 out8(PIT_MODE, 0x34); /* Set mode 2 and wait for divisor bytes */ 23 out8(PIT_CH0, divisor & 0xff); /* Set low byte of divisor */ 24 out8(PIT_CH0, divisor >> 8); /* Set high byte of divisor */ 25} 26 27BOOT_CODE void pit_wait_wraparound(void) 28{ 29 uint16_t count; 30 uint16_t count_old; 31 32 out8(PIT_MODE, 0x00); 33 count = in8(PIT_CH0); 34 count |= (in8(PIT_CH0) << 8); 35 count_old = count; 36 37 while (count <= count_old) { 38 count_old = count; 39 out8(PIT_MODE, 0x00); 40 count = in8(PIT_CH0); 41 count |= (in8(PIT_CH0) << 8); 42 } 43} 44