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