Introduce the new timer subsystem.

Timer subsystem initialization code in core/timer.c

	Split the BIOS and RTDSC timer drivers from i386_timer.c

	Split arch/i386/firmware/pcbios/bios.c into the RTSDC
	timer driver and arch/i386/core/nap.c

	Split the headers properly:
		include/unistd.h - delay functions to be used by the
					gPXE core and drivers.

		include/gpxe/timer.h - the fimer subsystem interface
					to be used by the timer drivers
					and currticks() to be used by
					the code gPXE subsystems.

		include/latch.h	- removed
		include/timer.h - scheduled for removal. Some driver
					are using currticks, which is
					only for core subsystems.

Signed-off-by: Alexey Zaytsev <alexey.zaytsev@gmail.com>

src/arch/i386/drivers/timer_bios.c

@@ -0,0 +1,57 @@
+/*
+ * Etherboot routines for PCBIOS firmware.
+ *
+ * Body of routines taken from old pcbios.S
+ */
+
+#include <gpxe/init.h>
+#include <gpxe/timer.h>
+#include <stdio.h>
+#include <realmode.h>
+#include <bios.h>
+#include <bits/timer2.h>
+
+/* A bit faster actually, but we don't care. */
+#define	TIMER2_TICKS_PER_SEC	18
+
+/*
+ * Use direct memory access to BIOS variables, longword 0040:006C (ticks
+ * today) and byte 0040:0070 (midnight crossover flag) instead of calling
+ * timeofday BIOS interrupt.
+ */
+
+static tick_t bios_currticks ( void ) {
+	static int days = 0;
+	uint32_t ticks;
+	uint8_t midnight;
+
+	/* Re-enable interrupts so that the timer interrupt can occur */
+	__asm__ __volatile__ ( REAL_CODE ( "sti\n\t"
+					   "nop\n\t"
+					   "nop\n\t"
+					   "cli\n\t" ) : : );
+
+	get_real ( ticks, BDA_SEG, 0x006c );
+	get_real ( midnight, BDA_SEG, 0x0070 );
+
+	if ( midnight ) {
+		midnight = 0;
+		put_real ( midnight, BDA_SEG, 0x0070 );
+		days += 0x1800b0;
+	}
+
+	return ( (days + ticks) * (USECS_IN_SEC / TIMER2_TICKS_PER_SEC) );
+}
+
+static int bios_ts_init(void)
+{
+	DBG("BIOS timer installed\n");
+	return 0;
+}
+
+struct timer bios_ts __timer ( 02 ) = {
+	.init = bios_ts_init,
+	.udelay = i386_timer2_udelay,
+	.currticks = bios_currticks,
+};
+

src/arch/i386/drivers/timer_rtdsc.c

@@ -0,0 +1,90 @@
+
+#include <gpxe/init.h>
+#include <gpxe/timer.h>
+#include <stdio.h>
+#include <bits/cpu.h>
+#include <bits/timer2.h>
+#include <io.h>
+
+
+#define rdtsc(low,high) \
+     __asm__ __volatile__("rdtsc" : "=a" (low), "=d" (high))
+
+#define rdtscll(val) \
+     __asm__ __volatile__ ("rdtsc" : "=A" (val))
+
+static unsigned long long calibrate_tsc(void)
+{
+	uint32_t startlow, starthigh;
+	uint32_t endlow, endhigh;
+
+	rdtsc(startlow,starthigh);
+	i386_timer2_udelay(USECS_IN_MSEC/2);
+	rdtsc(endlow,endhigh);
+
+	/* 64-bit subtract - gcc just messes up with long longs */
+	/* XXX ORLY? Check it. */
+	__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 *= MSECS_IN_SEC*2;
+	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:
+	return 0;
+}
+static uint32_t clocks_per_second = 0;
+
+static tick_t rtdsc_currticks(void)
+{
+	uint32_t clocks_high, clocks_low;
+	uint32_t currticks;
+
+	/* Read the Time Stamp Counter */
+	rdtsc(clocks_low, clocks_high);
+
+	/* currticks = clocks / clocks_per_tick; */
+	__asm__("divl %1"
+		:"=a" (currticks)
+		:"r" (clocks_per_second/USECS_IN_SEC), "0" (clocks_low), "d" (clocks_high));
+
+	return currticks;
+}
+
+static int rtdsc_ts_init(void)
+{
+
+	struct cpuinfo_x86 cpu_info;
+
+	get_cpuinfo(&cpu_info);
+	if (cpu_info.features & X86_FEATURE_TSC) {
+		clocks_per_second = calibrate_tsc();
+		if (clocks_per_second) {
+			DBG("RTDSC Ticksource installed. CPU running at %ld Mhz\n",
+				clocks_per_second/(1000*1000));
+			return 0;
+		}
+	}
+
+	printf("RTDSC timer not available on this machine.\n");
+	return 1;
+}
+
+struct timer rtdsc_ts __timer (01) = {
+	.init = rtdsc_ts_init,
+	.udelay = generic_currticks_udelay,
+	.currticks = rtdsc_currticks,
+};
+