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+/*
+ * This file is part of the libpayload project.
+ *
+ * Copyright (C) 2007 Uwe Hermann <uwe@hermann-uwe.de>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/*
+ * Datasheet:
+ * - Name: 82C54 CHMOS Programmable Interval Timer
+ * - PDF: http://www.intel.com/design/archives/periphrl/docs/23124406.pdf
+ * - Order number: 231244-006
+ */
+
+#include "local.h"
+
+#define I82C54_CONTROL_WORD_REGISTER 0x43 /* Write-only. */
+
+#define I82C54_COUNTER0 0x40
+#define I82C54_COUNTER1 0x41
+#define I82C54_COUNTER2 0x42
+
+#define PC_SPEAKER_PORT 0x61
+
+/**
+ * Use the PC speaker to create a tone/sound of the specified frequency.
+ *
+ * The Intel 82C54 CHMOS Programmable Interval Timer (PIT) provides a
+ * superset of the functions of the original Intel 8253/8254 PIT. It has
+ * three programmable counters/timers (counter 0, 1, and 2). Counter 2 can
+ * be used to generate tones/sounds of various frequencies and duration.
+ *
+ * See also:
+ * - http://en.wikipedia.org/wiki/Pc_speaker
+ * - http://en.wikipedia.org/wiki/Intel_8253
+ *
+ * @param freq The frequency of the tone.
+ */
+void speaker_enable(u16 freq)
+{
+ /* Select counter 2. Read/write LSB first, then MSB. Use mode 3
+ (square wave generator). Use a 16bit binary counter. */
+ outb(0xb6, I82C54_CONTROL_WORD_REGISTER);
+
+ /* Set the desired tone frequency. */
+ outb((u8)(freq & 0x00ff), I82C54_COUNTER2); /* LSB. */
+ outb((u8)(freq >> 8), I82C54_COUNTER2); /* MSB. */
+
+ /* Enable the PC speaker (set bits 0 and 1). */
+ outb(inb(PC_SPEAKER_PORT) | 0x03, PC_SPEAKER_PORT);
+}
+
+/**
+ * Disable the PC speaker.
+ */
+void speaker_disable(void)
+{
+ /* Disable the PC speaker (clear bits 0 and 1). */
+ outb(inb(PC_SPEAKER_PORT) & 0xfc, PC_SPEAKER_PORT);
+}
+
+/**
+ * Use the PC speaker to create a tone/beep of the specified frequency
+ * and duration.
+ *
+ * Wait for a short amount of time after the beep to make it distinguishable
+ * from the next beep (if any).
+ *
+ * @param freq The frequency of the tone/beep.
+ * @param duration The duration of the tone/beep in milliseconds.
+ */
+void speaker_tone(u16 freq, unsigned int duration)
+{
+ speaker_enable(freq);
+ mdelay(duration);
+ speaker_disable();
+ mdelay(100);
+}