arch/x86/lib/i8254.c

   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 }