diff options
Diffstat (limited to 'qemu/roms/ipxe/src/arch/x86/core/pit8254.c')
-rw-r--r-- | qemu/roms/ipxe/src/arch/x86/core/pit8254.c | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/qemu/roms/ipxe/src/arch/x86/core/pit8254.c b/qemu/roms/ipxe/src/arch/x86/core/pit8254.c new file mode 100644 index 000000000..da2099263 --- /dev/null +++ b/qemu/roms/ipxe/src/arch/x86/core/pit8254.c @@ -0,0 +1,70 @@ +/* + * Copyright (C) 2015 Michael Brown <mbrown@fensystems.co.uk>. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; either version 2 of the + * License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301, USA. + * + * You can also choose to distribute this program under the terms of + * the Unmodified Binary Distribution Licence (as given in the file + * COPYING.UBDL), provided that you have satisfied its requirements. + */ + +FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL ); + +#include <assert.h> +#include <ipxe/io.h> +#include <ipxe/pit8254.h> + +/** @file + * + * 8254 Programmable Interval Timer + * + */ + +/** + * Delay for a fixed number of timer ticks using the speaker channel + * + * @v ticks Number of timer ticks for which to delay + */ +void pit8254_speaker_delay ( unsigned int ticks ) { + uint8_t spkr; + uint8_t cmd; + uint8_t low; + uint8_t high; + + /* Sanity check */ + assert ( ticks <= 0xffff ); + + /* Disable speaker, set speaker channel gate input high */ + spkr = inb ( PIT8254_SPKR ); + spkr &= ~PIT8254_SPKR_ENABLE; + spkr |= PIT8254_SPKR_GATE; + outb ( spkr, PIT8254_SPKR ); + + /* Program speaker channel to "interrupt" on terminal count */ + cmd = ( PIT8254_CMD_CHANNEL ( PIT8254_CH_SPKR ) | + PIT8254_CMD_ACCESS_LOHI | PIT8254_CMD_OP_TERMINAL | + PIT8254_CMD_BINARY ); + low = ( ( ticks >> 0 ) & 0xff ); + high = ( ( ticks >> 8 ) & 0xff ); + outb ( cmd, PIT8254_CMD ); + outb ( low, PIT8254_DATA ( PIT8254_CH_SPKR ) ); + outb ( high, PIT8254_DATA ( PIT8254_CH_SPKR ) ); + + /* Wait for channel to "interrupt" */ + do { + spkr = inb ( PIT8254_SPKR ); + } while ( ! ( spkr & PIT8254_SPKR_OUT ) ); +} |