1 files changed, 276 insertions, 0 deletions

diff --git a/drivers/char/ftape/lowlevel/ftape-calibr.c b/drivers/char/ftape/lowlevel/ftape-calibr.c
new file mode 100644
index 000000000000..956b2586e138
--- /dev/null
+++ b/drivers/char/ftape/lowlevel/ftape-calibr.c
@@ -0,0 +1,276 @@
+/*
+ *      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/jiffies.h>
+#include <asm/system.h>
+#include <asm/io.h>
+#if defined(__alpha__)
+# include <asm/hwrpb.h>
+#elif defined(__x86_64__)
+# include <asm/msr.h>
+# include <asm/timex.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__) && !defined(__x86_64__)
+# error Ftape is not implemented for this architecture!
+#endif
+
+#if defined(__alpha__) || defined(__x86_64__)
+static unsigned long ps_per_cycle = 0;
+#endif
+
+static spinlock_t calibr_lock;
+
+/*
+ * 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 it's 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(__x86_64__)
+        unsigned long r;
+        rdtscl(r);
+        return r;
+#elif defined(__i386__)
+
+/*
+ * Note that there is some time between counter underflowing and jiffies
+ * increasing, so the code below won't always give correct output.
+ * -Vojtech
+ */
+
+        unsigned long flags;
+        __u16 lo;
+        __u16 hi;
+
+        spin_lock_irqsave(&calibr_lock, flags);
+        outb_p(0x00, 0x43);     /* latch the count ASAP */
+        lo = inb_p(0x40);       /* read the latched count */
+        lo |= inb(0x40) << 8;
+        hi = jiffies;
+        spin_unlock_irqrestore(&calibr_lock, flags);
+        return ((hi + 1) * (unsigned int) LATCH) - lo;  /* downcounter ! */
+#endif
+}
+
+static unsigned int short_ftape_timestamp(void)
+{
+#if defined(__alpha__) || defined(__x86_64__)
+        return ftape_timestamp();
+#elif defined(__i386__)
+        unsigned int count;
+        unsigned long flags;
+ 
+        spin_lock_irqsave(&calibr_lock, flags);
+        outb_p(0x00, 0x43);     /* latch the count ASAP */
+        count = inb_p(0x40);    /* read the latched count */
+        count |= inb(0x40) << 8;
+        spin_unlock_irqrestore(&calibr_lock, flags);
+        return (LATCH - count); /* normal: downcounter */
+#endif
+}
+
+static unsigned int diff(unsigned int t0, unsigned int t1)
+{
+#if defined(__alpha__) || defined(__x86_64__)
+        return (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__) || defined(__x86_64__)
+        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);
+
+        spin_lock_irqsave(&calibr_lock, flags);
+        t0 = short_ftape_timestamp();
+        for (i = 0; i < 1000; ++i) {
+                status = inb(fdc.msr);
+        }
+        t1 = short_ftape_timestamp();
+        spin_unlock_irqrestore(&calibr_lock, flags);
+        TRACE(ft_t_info, "inb() duration: %d nsec", ftape_timediff(t0, t1));
+        TRACE_EXIT;
+}
+
+static void init_clock(void)
+{
+        TRACE_FUN(ft_t_any);
+
+#if defined(__x86_64__)
+        ps_per_cycle = 1000000000UL / cpu_khz;
+#elif defined(__alpha__)
+        extern struct hwrpb_struct *hwrpb;
+        ps_per_cycle = (1000*1000*1000*1000UL) / hwrpb->cycle_freq;
+#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 */
+                spin_lock_irqsave(&calibr_lock, flags);
+                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);
+                spin_unlock_irqrestore(&calibr_lock, 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__) || defined(__x86_64__)
+                /*
+                 * 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;
+}