2 * Copyright (C) 2015 Michael Brown <mbrown@fensystems.co.uk>.
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation; either version 2 of the
7 * License, or (at your option) any later version.
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
19 * You can also choose to distribute this program under the terms of
20 * the Unmodified Binary Distribution Licence (as given in the file
21 * COPYING.UBDL), provided that you have satisfied its requirements.
24 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
28 #include <ipxe/pit8254.h>
32 * 8254 Programmable Interval Timer
37 * Delay for a fixed number of timer ticks using the speaker channel
39 * @v ticks Number of timer ticks for which to delay
41 void pit8254_speaker_delay ( unsigned int ticks ) {
48 assert ( ticks <= 0xffff );
50 /* Disable speaker, set speaker channel gate input high */
51 spkr = inb ( PIT8254_SPKR );
52 spkr &= ~PIT8254_SPKR_ENABLE;
53 spkr |= PIT8254_SPKR_GATE;
54 outb ( spkr, PIT8254_SPKR );
56 /* Program speaker channel to "interrupt" on terminal count */
57 cmd = ( PIT8254_CMD_CHANNEL ( PIT8254_CH_SPKR ) |
58 PIT8254_CMD_ACCESS_LOHI | PIT8254_CMD_OP_TERMINAL |
60 low = ( ( ticks >> 0 ) & 0xff );
61 high = ( ( ticks >> 8 ) & 0xff );
62 outb ( cmd, PIT8254_CMD );
63 outb ( low, PIT8254_DATA ( PIT8254_CH_SPKR ) );
64 outb ( high, PIT8254_DATA ( PIT8254_CH_SPKR ) );
66 /* Wait for channel to "interrupt" */
68 spkr = inb ( PIT8254_SPKR );
69 } while ( ! ( spkr & PIT8254_SPKR_OUT ) );