[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>

4 files changed, 6 insertions, 107 deletions

diff --git a/src/arch/i386/core/rdtsc_timer.c b/src/arch/i386/core/rdtsc_timer.c
index 2f31afc66..f7b4b9af1 100644
--- a/src/arch/i386/core/rdtsc_timer.c
+++ b/src/arch/i386/core/rdtsc_timer.c
@@ -27,7 +27,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <assert.h>
 #include <ipxe/timer.h>
-#include <ipxe/timer2.h>
+#include <ipxe/pit8254.h>
 
 /**
  * Number of TSC ticks per microsecond
@@ -56,10 +56,10 @@ static void rdtsc_udelay ( unsigned long usecs ) {
 			elapsed = ( currticks() - start );
 		} while ( elapsed < ( usecs * rdtsc_ticks_per_usec ) );
 	} else {
-		/* Not yet calibrated; use timer2 and calibrate
+		/* Not yet calibrated; use 8254 PIT and calibrate
 		 * based on result.
 		 */
-		timer2_udelay ( usecs );
+		pit8254_udelay ( usecs );
 		elapsed = ( currticks() - start );
 		rdtsc_ticks_per_usec = ( elapsed / usecs );
 		DBG ( "RDTSC timer calibrated: %ld ticks in %ld usecs "
diff --git a/src/arch/i386/core/timer2.c b/src/arch/i386/core/timer2.c
deleted file mode 100644
index 077866562..000000000
--- a/src/arch/i386/core/timer2.c
+++ /dev/null
@@ -1,87 +0,0 @@
-/*
- * arch/i386/core/i386_timer.c
- *
- * Use the "System Timer 2" to implement the udelay callback in
- * the BIOS timer driver. Also used to calibrate the clock rate
- * in the RTDSC timer driver.
- * 
- * 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, or (at
- * your option) any later version.
- */
-
-FILE_LICENCE ( GPL2_OR_LATER );
-
-#include <stddef.h>
-#include <ipxe/timer2.h>
-#include <ipxe/io.h>
-
-/* Timers tick over at this rate */
-#define TIMER2_TICKS_PER_SEC	1193180U
-
-/* Parallel Peripheral Controller Port B */
-#define	PPC_PORTB	0x61
-
-/* Meaning of the port bits */
-#define	PPCB_T2OUT	0x20	/* Bit 5 */
-#define	PPCB_SPKR	0x02	/* Bit 1 */
-#define	PPCB_T2GATE	0x01	/* Bit 0 */
-
-/* Ports for the 8254 timer chip */
-#define	TIMER2_PORT	0x42
-#define	TIMER_MODE_PORT	0x43
-
-/* Meaning of the mode bits */
-#define	TIMER0_SEL	0x00
-#define	TIMER1_SEL	0x40
-#define	TIMER2_SEL	0x80
-#define	READBACK_SEL	0xC0
-
-#define	LATCH_COUNT	0x00
-#define	LOBYTE_ACCESS	0x10
-#define	HIBYTE_ACCESS	0x20
-#define	WORD_ACCESS	0x30
-
-#define	MODE0		0x00
-#define	MODE1		0x02
-#define	MODE2		0x04
-#define	MODE3		0x06
-#define	MODE4		0x08
-#define	MODE5		0x0A
-
-#define	BINARY_COUNT	0x00
-#define	BCD_COUNT	0x01
-
-static void load_timer2 ( unsigned int ticks ) {
-	/*
-	 * Now let's take care of PPC channel 2
-	 *
-	 * Set the Gate high, program PPC channel 2 for mode 0,
-	 * (interrupt on terminal count mode), binary count,
-	 * load 5 * LATCH count, (LSB and MSB) to begin countdown.
-	 *
-	 * Note some implementations have a bug where the high bits byte
-	 * of channel 2 is ignored.
-	 */
-	/* Set up the timer gate, turn off the speaker */
-	/* Set the Gate high, disable speaker */
-	outb((inb(PPC_PORTB) & ~PPCB_SPKR) | PPCB_T2GATE, PPC_PORTB);
-	/* binary, mode 0, LSB/MSB, Ch 2 */
-	outb(TIMER2_SEL|WORD_ACCESS|MODE0|BINARY_COUNT, TIMER_MODE_PORT);
-	/* LSB of ticks */
-	outb(ticks & 0xFF, TIMER2_PORT);
-	/* MSB of ticks */
-	outb(ticks >> 8, TIMER2_PORT);
-}
-
-static int timer2_running ( void ) {
-	return ((inb(PPC_PORTB) & PPCB_T2OUT) == 0);
-}
-
-void timer2_udelay ( unsigned long usecs ) {
-	load_timer2 ( ( usecs * TIMER2_TICKS_PER_SEC ) / ( 1000 * 1000 ) );
-	while (timer2_running()) {
-		/* Do nothing */
-	}
-}
diff --git a/src/arch/i386/include/ipxe/bios_timer.h b/src/arch/i386/include/ipxe/bios_timer.h
index f9fc80412..407780a6a 100644
--- a/src/arch/i386/include/ipxe/bios_timer.h
+++ b/src/arch/i386/include/ipxe/bios_timer.h
@@ -15,7 +15,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #define TIMER_PREFIX_pcbios __pcbios_
 #endif
 
-#include <ipxe/timer2.h>
+#include <ipxe/pit8254.h>
 
 /**
  * Delay for a fixed number of microseconds
@@ -25,9 +25,9 @@ FILE_LICENCE ( GPL2_OR_LATER );
 static inline __always_inline void
 TIMER_INLINE ( pcbios, udelay ) ( unsigned long usecs ) {
 	/* BIOS timer is not high-resolution enough for udelay(), so
-	 * we use timer2
+	 * we use the 8254 Programmable Interval Timer.
 	 */
-	timer2_udelay ( usecs );
+	pit8254_udelay ( usecs );
 }
 
 /**
diff --git a/src/arch/i386/include/ipxe/timer2.h b/src/arch/i386/include/ipxe/timer2.h
deleted file mode 100644
index 322a3ed59..000000000
--- a/src/arch/i386/include/ipxe/timer2.h
+++ /dev/null
@@ -1,14 +0,0 @@
-#ifndef _IPXE_TIMER2_H
-#define _IPXE_TIMER2_H
-
-/** @file
- *
- * Timer chip control
- *
- */
-
-FILE_LICENCE ( GPL2_OR_LATER );
-
-extern void timer2_udelay ( unsigned long usecs );
-
-#endif /* _IPXE_TIMER2_H */