1 // SPDX-License-Identifier: GPL-2.0+
4 * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
11 #define TIMER1_VALUE 18 /* 15.6us */
12 #define TIMER2_VALUE 0x0a8e /* 440Hz */
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.
21 outb(PIT_CMD_CTR1 | PIT_CMD_LOW | PIT_CMD_MODE2,
22 PIT_BASE + PIT_COMMAND);
23 outb(TIMER1_VALUE, PIT_BASE + PIT_T1);
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.
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);