/* * (C) Copyright 2002 * Daniel Engström, Omicron Ceti AB, * * SPDX-License-Identifier: GPL-2.0+ */ #include #include #include #define TIMER1_VALUE 18 /* 15.6us */ #define TIMER2_VALUE 0x0a8e /* 440Hz */ int i8254_init(void) { /* * Initialize counter 1, used to refresh request signal. * This is required for legacy purpose as some codes like * vgabios utilizes counter 1 to provide delay functionality. */ outb(PIT_CMD_CTR1 | PIT_CMD_LOW | PIT_CMD_MODE2, PIT_BASE + PIT_COMMAND); outb(TIMER1_VALUE, PIT_BASE + PIT_T1); /* * Initialize counter 2, used to drive the speaker. * To start a beep, set both bit0 and bit1 of port 0x61. * To stop it, clear both bit0 and bit1 of port 0x61. */ outb(PIT_CMD_CTR2 | PIT_CMD_BOTH | PIT_CMD_MODE3, PIT_BASE + PIT_COMMAND); outb(TIMER2_VALUE & 0xff, PIT_BASE + PIT_T2); outb(TIMER2_VALUE >> 8, PIT_BASE + PIT_T2); return 0; }