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 BEEP_FREQUENCY_HZ 440
13 #define SYSCTL_PORTB 0x61
14 #define PORTB_BEEP_ENABLE 0x3
16 static void i8254_set_beep_freq(uint frequency_hz)
20 countdown = PIT_TICK_RATE / frequency_hz;
22 outb(countdown & 0xff, PIT_BASE + PIT_T2);
23 outb((countdown >> 8) & 0xff, PIT_BASE + PIT_T2);
29 * Initialize counter 1, used to refresh request signal.
30 * This is required for legacy purpose as some codes like
31 * vgabios utilizes counter 1 to provide delay functionality.
33 outb(PIT_CMD_CTR1 | PIT_CMD_LOW | PIT_CMD_MODE2,
34 PIT_BASE + PIT_COMMAND);
35 outb(TIMER1_VALUE, PIT_BASE + PIT_T1);
38 * Initialize counter 2, used to drive the speaker.
39 * To start a beep, set both bit0 and bit1 of port 0x61.
40 * To stop it, clear both bit0 and bit1 of port 0x61.
42 outb(PIT_CMD_CTR2 | PIT_CMD_BOTH | PIT_CMD_MODE3,
43 PIT_BASE + PIT_COMMAND);
44 i8254_set_beep_freq(BEEP_FREQUENCY_HZ);
49 int i8254_enable_beep(uint frequency_hz)
54 /* make sure i8254 is setup correctly before generating beeps */
55 outb(PIT_CMD_CTR2 | PIT_CMD_BOTH | PIT_CMD_MODE3,
56 PIT_BASE + PIT_COMMAND);
58 i8254_set_beep_freq(frequency_hz);
59 setio_8(SYSCTL_PORTB, PORTB_BEEP_ENABLE);
64 void i8254_disable_beep(void)
66 clrio_8(SYSCTL_PORTB, PORTB_BEEP_ENABLE);