[timer] Rewrite the 8254 Programmable Interval Timer support

The 8254 timer code (used to implement udelay()) has an unknown
provenance.  Rewrite this code to avoid potential licensing
uncertainty.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 66 insertions, 0 deletions

diff --git a/src/arch/x86/core/pit8254.c b/src/arch/x86/core/pit8254.c
new file mode 100644
index 000000000..66c71a744
--- /dev/null
+++ b/src/arch/x86/core/pit8254.c
@@ -0,0 +1,66 @@
+/*
+ * 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.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#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 ) );
+}