/*
* 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;
}
