arch/x86/lib/i8254.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * (C) Copyright 2002
   4  * Daniel Engström, Omicron Ceti AB, <daniel@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 }