1 /* 2 * (C) Copyright 2002 3 * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se> 4 * 5 * SPDX-License-Identifier: GPL-2.0+ 6 */ 7 8 #include <common.h> 9 #include <asm/io.h> 10 #include <asm/i8254.h> 11 12 #define TIMER1_VALUE 18 /* 15.6us */ 13 #define TIMER2_VALUE 0x0a8e /* 440Hz */ 14 15 int i8254_init(void) 16 { 17 /* 18 * Initialize counter 1, used to refresh request signal. 19 * This is required for legacy purpose as some codes like 20 * vgabios utilizes counter 1 to provide delay functionality. 21 */ 22 outb(PIT_CMD_CTR1 | PIT_CMD_LOW | PIT_CMD_MODE2, 23 PIT_BASE + PIT_COMMAND); 24 outb(TIMER1_VALUE, PIT_BASE + PIT_T1); 25 26 /* 27 * Initialize counter 2, used to drive the speaker. 28 * To start a beep, set both bit0 and bit1 of port 0x61. 29 * To stop it, clear both bit0 and bit1 of port 0x61. 30 */ 31 outb(PIT_CMD_CTR2 | PIT_CMD_BOTH | PIT_CMD_MODE3, 32 PIT_BASE + PIT_COMMAND); 33 outb(TIMER2_VALUE & 0xff, PIT_BASE + PIT_T2); 34 outb(TIMER2_VALUE >> 8, PIT_BASE + PIT_T2); 35 36 return 0; 37 } 38