Initial revision

src/arch/i386/core/i386_timer.c

@@ -0,0 +1,191 @@
+/* A couple of routines to implement a low-overhead timer for drivers */
+
+ /*
+ * 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.
+ */
+
+#include	"etherboot.h"
+#include	"timer.h"
+#include	"latch.h"
+
+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);
+}
+
+#if !defined(CONFIG_TSC_CURRTICKS)
+void setup_timers(void)
+{
+	return;
+}
+
+void load_timer2(unsigned int ticks)
+{
+	return __load_timer2(ticks);
+}
+
+int timer2_running(void)
+{
+	return __timer2_running();
+}
+
+void ndelay(unsigned int nsecs)
+{
+	waiton_timer2((nsecs * CLOCK_TICK_RATE)/1000000000);
+}
+void udelay(unsigned int usecs)
+{
+	waiton_timer2((usecs * TICKS_PER_MS)/1000);
+}
+#endif /* !defined(CONFIG_TSC_CURRTICKS) */
+
+#if defined(CONFIG_TSC_CURRTICKS)
+
+#define rdtsc(low,high) \
+     __asm__ __volatile__("rdtsc" : "=a" (low), "=d" (high))
+
+#define rdtscll(val) \
+     __asm__ __volatile__ ("rdtsc" : "=A" (val))
+
+
+/* Number of clock ticks to time with the rtc */
+#define LATCH 0xFF
+
+#define LATCHES_PER_SEC ((CLOCK_TICK_RATE + (LATCH/2))/LATCH)
+#define TICKS_PER_LATCH ((LATCHES_PER_SEC + (TICKS_PER_SEC/2))/TICKS_PER_SEC)
+
+static void sleep_latch(void)
+{
+	__load_timer2(LATCH);
+	while(__timer2_running());
+}
+
+/* ------ Calibrate the TSC ------- 
+ * Time how long it takes to excute a loop that runs in known time.
+ * And find the convertion needed to get to CLOCK_TICK_RATE
+ */
+
+
+static unsigned long long calibrate_tsc(void)
+{
+	unsigned long startlow, starthigh;
+	unsigned long endlow, endhigh;
+	
+	rdtsc(startlow,starthigh);
+	sleep_latch();
+	rdtsc(endlow,endhigh);
+
+	/* 64-bit subtract - gcc just messes up with long longs */
+	__asm__("subl %2,%0\n\t"
+		"sbbl %3,%1"
+		:"=a" (endlow), "=d" (endhigh)
+		:"g" (startlow), "g" (starthigh),
+		"0" (endlow), "1" (endhigh));
+	
+	/* Error: ECPUTOOFAST */
+	if (endhigh)
+		goto bad_ctc;
+	
+	endlow *= TICKS_PER_LATCH;
+	return endlow;
+
+	/*
+	 * The CTC wasn't reliable: we got a hit on the very first read,
+	 * or the CPU was so fast/slow that the quotient wouldn't fit in
+	 * 32 bits..
+	 */
+bad_ctc:
+	printf("bad_ctc\n");
+	return 0;
+}
+
+static unsigned long clocks_per_tick;
+void setup_timers(void)
+{
+	if (!clocks_per_tick) {
+		clocks_per_tick = calibrate_tsc();
+		/* Display the CPU Mhz to easily test if the calibration was bad */
+		printf("CPU %ld Mhz\n", (clocks_per_tick/1000 * TICKS_PER_SEC)/1000);
+	}
+}
+
+unsigned long currticks(void)
+{
+	unsigned long clocks_high, clocks_low;
+	unsigned long currticks;
+	/* Read the Time Stamp Counter */
+	rdtsc(clocks_low, clocks_high);
+
+	/* currticks = clocks / clocks_per_tick; */
+	__asm__("divl %1"
+		:"=a" (currticks)
+		:"r" (clocks_per_tick), "0" (clocks_low), "d" (clocks_high));
+
+
+	return currticks;
+}
+
+static unsigned long long timer_timeout;
+static int __timer_running(void)
+{
+	unsigned long long now;
+	rdtscll(now);
+	return now < timer_timeout;
+}
+
+void udelay(unsigned int usecs)
+{
+	unsigned long long now;
+	rdtscll(now);
+	timer_timeout = now + usecs * ((clocks_per_tick * TICKS_PER_SEC)/(1000*1000));
+	while(__timer_running());
+}
+void ndelay(unsigned int nsecs)
+{
+	unsigned long long now;
+	rdtscll(now);
+	timer_timeout = now + nsecs * ((clocks_per_tick * TICKS_PER_SEC)/(1000*1000*1000));
+	while(__timer_running());
+}
+
+void load_timer2(unsigned int timer2_ticks)
+{
+	unsigned long long now;
+	unsigned long clocks;
+	rdtscll(now);
+	clocks = timer2_ticks * ((clocks_per_tick * TICKS_PER_SEC)/CLOCK_TICK_RATE);
+	timer_timeout = now + clocks;
+}
+
+int timer2_running(void)
+{
+	return __timer_running();
+}
+
+#endif /* RTC_CURRTICKS */