xref: /openbmc/u-boot/arch/x86/lib/i8254.c (revision 0a61ee88)
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