patch-2.1.66 linux/drivers/char/ftape/lowlevel/ftape-calibr.c

• Lines: 290
• Date: Tue Nov 25 14:45:27 1997
• Orig file: v2.1.65/linux/drivers/char/ftape/lowlevel/ftape-calibr.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.1.65/linux/drivers/char/ftape/lowlevel/ftape-calibr.c linux/drivers/char/ftape/lowlevel/ftape-calibr.c
@@ -0,0 +1,289 @@
+/*
+ *      Copyright (C) 1993-1996 Bas Laarhoven.
+
+ 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.
+
+ 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; see the file COPYING.  If not, write to
+ the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ *
+ * $Source: /homes/cvs/ftape-stacked/ftape/lowlevel/ftape-calibr.c,v $
+ * $Revision: 1.2 $
+ * $Date: 1997/10/05 19:18:08 $
+ *
+ *      GP calibration routine for processor speed dependent
+ *      functions.
+ */
+
+#include <linux/config.h>
+#include <linux/errno.h>
+#include <linux/sched.h>
+#include <asm/system.h>
+#include <asm/io.h>
+#if defined(__alpha__)
+# include <asm/hwrpb.h>
+#elif defined(__i386__)
+# include <linux/timex.h>
+#endif
+#include <linux/ftape.h>
+#include "../lowlevel/ftape-tracing.h"
+#include "../lowlevel/ftape-calibr.h"
+#include "../lowlevel/fdc-io.h"
+
+#undef DEBUG
+
+#if !defined(__alpha__) && !defined(__i386__)
+# error Ftape is not implemented for this architecture!
+#endif
+
+#if defined(__alpha__)
+static unsigned long ps_per_cycle = 0;
+#endif
+
+/*
+ * Note: On Intel PCs, the clock ticks at 100 Hz (HZ==100) which is
+ * too slow for certain timeouts (and that clock doesn't even tick
+ * when interrupts are disabled).  For that reason, the 8254 timer is
+ * used directly to implement fine-grained timeouts.  However, on
+ * Alpha PCs, the 8254 is *not* used to implement the clock tick
+ * (which is 1024 Hz, normally) and the 8254 timer runs at some
+ * "random" frequency (it seems to run at 18Hz, but its not safe to
+ * rely on this value).  Instead, we use the Alpha's "rpcc"
+ * instruction to read cycle counts.  As this is a 32 bit counter,
+ * it will overflow only once per 30 seconds (on a 200MHz machine),
+ * which is plenty.
+ */
+
+unsigned int ftape_timestamp(void)
+{
+#if defined(__alpha__)
+	unsigned long r;
+
+	asm volatile ("rpcc %0" : "=r" (r));
+	return r;
+#elif defined(__i386__)
+	unsigned long flags;
+	__u16 lo;
+	__u16 hi;
+
+	save_flags(flags);
+	cli();
+	outb_p(0x00, 0x43);	/* latch the count ASAP */
+	lo = inb_p(0x40);	/* read the latched count */
+	lo |= inb(0x40) << 8;
+	hi = jiffies;
+	restore_flags(flags);
+	return ((hi + 1) * (unsigned int) LATCH) - lo;  /* downcounter ! */
+#endif
+}
+
+static unsigned int short_ftape_timestamp(void)
+{
+#if defined(__alpha__)
+	return ftape_timestamp();
+#elif defined(__i386__)
+	unsigned int count;
+ 	unsigned long flags;
+ 
+ 	save_flags(flags);
+ 	cli();
+ 	outb_p(0x00, 0x43);	/* latch the count ASAP */
+	count = inb_p(0x40);	/* read the latched count */
+	count |= inb(0x40) << 8;
+ 	restore_flags(flags);
+	return (LATCH - count);	/* normal: downcounter */
+#endif
+}
+
+static unsigned int diff(unsigned int t0, unsigned int t1)
+{
+#if defined(__alpha__)
+	return (t1 <= t0) ? t1 + (1UL << 32) - t0 : t1 - t0;
+#elif defined(__i386__)
+	/*
+	 * This is tricky: to work for both short and full ftape_timestamps
+	 * we'll have to discriminate between these.
+	 * If it _looks_ like short stamps with wrapping around we'll
+	 * asume it are. This will generate a small error if it really
+	 * was a (very large) delta from full ftape_timestamps.
+	 */
+	return (t1 <= t0 && t0 <= LATCH) ? t1 + LATCH - t0 : t1 - t0;
+#endif
+}
+
+static unsigned int usecs(unsigned int count)
+{
+#if defined(__alpha__)
+	return (ps_per_cycle * count) / 1000000UL;
+#elif defined(__i386__)
+	return (10000 * count) / ((CLOCK_TICK_RATE + 50) / 100);
+#endif
+}
+
+unsigned int ftape_timediff(unsigned int t0, unsigned int t1)
+{
+	/*
+	 *  Calculate difference in usec for ftape_timestamp results t0 & t1.
+	 *  Note that on the i386 platform with short time-stamps, the
+	 *  maximum allowed timespan is 1/HZ or we'll lose ticks!
+	 */
+	return usecs(diff(t0, t1));
+}
+
+/*      To get an indication of the I/O performance,
+ *      measure the duration of the inb() function.
+ */
+static void time_inb(void)
+{
+	int i;
+	int t0, t1;
+	unsigned long flags;
+	int status;
+	TRACE_FUN(ft_t_any);
+
+	save_flags(flags);
+	cli();
+	t0 = short_ftape_timestamp();
+	for (i = 0; i < 1000; ++i) {
+		status = inb(fdc.msr);
+	}
+	t1 = short_ftape_timestamp();
+	restore_flags(flags);
+	TRACE(ft_t_info, "inb() duration: %d nsec", ftape_timediff(t0, t1));
+	TRACE_EXIT;
+}
+
+static void init_clock(void)
+{
+#if defined(__i386__)
+	unsigned int t;
+	int i;
+	TRACE_FUN(ft_t_any);
+
+	/*  Haven't studied on why, but there sometimes is a problem
+	 *  with the tick timer readout. The two bytes get swapped.
+	 *  This hack solves that problem by doing one extra input.
+	 */
+	for (i = 0; i < 1000; ++i) {
+		t = short_ftape_timestamp();
+		if (t > LATCH) {
+			inb_p(0x40);	/* get in sync again */
+			TRACE(ft_t_warn, "clock counter fixed");
+			break;
+		}
+	}
+#elif defined(__alpha__)
+#if CONFIG_FT_ALPHA_CLOCK == 0
+#error You must define and set CONFIG_FT_ALPHA_CLOCK in the Makefile !
+#endif
+	extern struct hwrpb_struct *hwrpb;
+	TRACE_FUN(ft_t_any);
+
+	if (hwrpb->cycle_freq != 0) {
+		ps_per_cycle = (1000*1000*1000*1000UL) / hwrpb->cycle_freq;
+	} else {
+		/*
+		 * HELP:  Linux 2.0.x doesn't set cycle_freq on my noname !
+		 */
+		ps_per_cycle = (1000*1000*1000*1000UL) / CONFIG_FT_ALPHA_CLOCK;
+	}
+#endif
+	TRACE_EXIT;
+}
+
+/*
+ *      Input:  function taking int count as parameter.
+ *              pointers to calculated calibration variables.
+ */
+void ftape_calibrate(char *name,
+		    void (*fun) (unsigned int), 
+		    unsigned int *calibr_count, 
+		    unsigned int *calibr_time)
+{
+	static int first_time = 1;
+	int i;
+	unsigned int tc = 0;
+	unsigned int count;
+	unsigned int time;
+#if defined(__i386__)
+	unsigned int old_tc = 0;
+	unsigned int old_count = 1;
+	unsigned int old_time = 1;
+#endif
+	TRACE_FUN(ft_t_flow);
+
+	if (first_time) {             /* get idea of I/O performance */
+		init_clock();
+		time_inb();
+		first_time = 0;
+	}
+	/*    value of timeout must be set so that on very slow systems
+	 *    it will give a time less than one jiffy, and on
+	 *    very fast systems it'll give reasonable precision.
+	 */
+
+	count = 40;
+	for (i = 0; i < 15; ++i) {
+		unsigned int t0;
+		unsigned int t1;
+		unsigned int once;
+		unsigned int multiple;
+		unsigned long flags;
+
+		*calibr_count =
+		*calibr_time = count;	/* set TC to 1 */
+		save_flags(flags);
+		cli();
+		fun(0);		/* dummy, get code into cache */
+		t0 = short_ftape_timestamp();
+		fun(0);		/* overhead + one test */
+		t1 = short_ftape_timestamp();
+		once = diff(t0, t1);
+		t0 = short_ftape_timestamp();
+		fun(count);		/* overhead + count tests */
+		t1 = short_ftape_timestamp();
+		multiple = diff(t0, t1);
+		restore_flags(flags);
+		time = ftape_timediff(0, multiple - once);
+		tc = (1000 * time) / (count - 1);
+		TRACE(ft_t_any, "once:%3d us,%6d times:%6d us, TC:%5d ns",
+			usecs(once), count - 1, usecs(multiple), tc);
+#if defined(__alpha__)
+		/*
+		 * Increase the calibration count exponentially until the
+		 * calibration time exceeds 100 ms.
+		 */
+		if (time >= 100*1000) {
+			break;
+		}
+#elif defined(__i386__)
+		/*
+		 * increase the count until the resulting time nears 2/HZ,
+		 * then the tc will drop sharply because we lose LATCH counts.
+		 */
+		if (tc <= old_tc / 2) {
+			time = old_time;
+			count = old_count;
+			break;
+		}
+		old_tc = tc;
+		old_count = count;
+		old_time = time;
+#endif
+		count *= 2;
+	}
+	*calibr_count = count - 1;
+	*calibr_time  = time;
+	TRACE(ft_t_info, "TC for `%s()' = %d nsec (at %d counts)",
+	     name, (1000 * *calibr_time) / *calibr_count, *calibr_count);
+	TRACE_EXIT;
+}