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276 lines
7.5 KiB
276 lines
7.5 KiB
/*
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* Copyright (C) 1993-1996 Bas Laarhoven.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; see the file COPYING. If not, write to
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the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* $Source: /homes/cvs/ftape-stacked/ftape/lowlevel/ftape-calibr.c,v $
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* $Revision: 1.2 $
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* $Date: 1997/10/05 19:18:08 $
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*
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* GP calibration routine for processor speed dependent
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* functions.
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*/
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#include <linux/config.h>
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#include <linux/errno.h>
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#include <linux/jiffies.h>
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#include <asm/system.h>
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#include <asm/io.h>
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#if defined(__alpha__)
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# include <asm/hwrpb.h>
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#elif defined(__x86_64__)
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# include <asm/msr.h>
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# include <asm/timex.h>
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#elif defined(__i386__)
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# include <linux/timex.h>
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#endif
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#include <linux/ftape.h>
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#include "../lowlevel/ftape-tracing.h"
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#include "../lowlevel/ftape-calibr.h"
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#include "../lowlevel/fdc-io.h"
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#undef DEBUG
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#if !defined(__alpha__) && !defined(__i386__) && !defined(__x86_64__)
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# error Ftape is not implemented for this architecture!
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#endif
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#if defined(__alpha__) || defined(__x86_64__)
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static unsigned long ps_per_cycle = 0;
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#endif
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static spinlock_t calibr_lock;
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/*
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* Note: On Intel PCs, the clock ticks at 100 Hz (HZ==100) which is
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* too slow for certain timeouts (and that clock doesn't even tick
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* when interrupts are disabled). For that reason, the 8254 timer is
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* used directly to implement fine-grained timeouts. However, on
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* Alpha PCs, the 8254 is *not* used to implement the clock tick
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* (which is 1024 Hz, normally) and the 8254 timer runs at some
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* "random" frequency (it seems to run at 18Hz, but it's not safe to
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* rely on this value). Instead, we use the Alpha's "rpcc"
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* instruction to read cycle counts. As this is a 32 bit counter,
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* it will overflow only once per 30 seconds (on a 200MHz machine),
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* which is plenty.
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*/
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unsigned int ftape_timestamp(void)
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{
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#if defined(__alpha__)
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unsigned long r;
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asm volatile ("rpcc %0" : "=r" (r));
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return r;
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#elif defined(__x86_64__)
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unsigned long r;
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rdtscl(r);
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return r;
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#elif defined(__i386__)
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/*
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* Note that there is some time between counter underflowing and jiffies
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* increasing, so the code below won't always give correct output.
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* -Vojtech
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*/
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unsigned long flags;
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__u16 lo;
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__u16 hi;
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spin_lock_irqsave(&calibr_lock, flags);
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outb_p(0x00, 0x43); /* latch the count ASAP */
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lo = inb_p(0x40); /* read the latched count */
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lo |= inb(0x40) << 8;
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hi = jiffies;
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spin_unlock_irqrestore(&calibr_lock, flags);
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return ((hi + 1) * (unsigned int) LATCH) - lo; /* downcounter ! */
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#endif
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}
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static unsigned int short_ftape_timestamp(void)
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{
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#if defined(__alpha__) || defined(__x86_64__)
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return ftape_timestamp();
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#elif defined(__i386__)
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unsigned int count;
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unsigned long flags;
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spin_lock_irqsave(&calibr_lock, flags);
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outb_p(0x00, 0x43); /* latch the count ASAP */
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count = inb_p(0x40); /* read the latched count */
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count |= inb(0x40) << 8;
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spin_unlock_irqrestore(&calibr_lock, flags);
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return (LATCH - count); /* normal: downcounter */
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#endif
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}
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static unsigned int diff(unsigned int t0, unsigned int t1)
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{
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#if defined(__alpha__) || defined(__x86_64__)
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return (t1 - t0);
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#elif defined(__i386__)
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/*
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* This is tricky: to work for both short and full ftape_timestamps
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* we'll have to discriminate between these.
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* If it _looks_ like short stamps with wrapping around we'll
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* asume it are. This will generate a small error if it really
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* was a (very large) delta from full ftape_timestamps.
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*/
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return (t1 <= t0 && t0 <= LATCH) ? t1 + LATCH - t0 : t1 - t0;
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#endif
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}
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static unsigned int usecs(unsigned int count)
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{
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#if defined(__alpha__) || defined(__x86_64__)
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return (ps_per_cycle * count) / 1000000UL;
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#elif defined(__i386__)
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return (10000 * count) / ((CLOCK_TICK_RATE + 50) / 100);
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#endif
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}
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unsigned int ftape_timediff(unsigned int t0, unsigned int t1)
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{
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/*
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* Calculate difference in usec for ftape_timestamp results t0 & t1.
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* Note that on the i386 platform with short time-stamps, the
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* maximum allowed timespan is 1/HZ or we'll lose ticks!
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*/
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return usecs(diff(t0, t1));
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}
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/* To get an indication of the I/O performance,
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* measure the duration of the inb() function.
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*/
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static void time_inb(void)
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{
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int i;
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int t0, t1;
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unsigned long flags;
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int status;
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TRACE_FUN(ft_t_any);
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spin_lock_irqsave(&calibr_lock, flags);
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t0 = short_ftape_timestamp();
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for (i = 0; i < 1000; ++i) {
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status = inb(fdc.msr);
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}
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t1 = short_ftape_timestamp();
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spin_unlock_irqrestore(&calibr_lock, flags);
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TRACE(ft_t_info, "inb() duration: %d nsec", ftape_timediff(t0, t1));
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TRACE_EXIT;
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}
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static void init_clock(void)
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{
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TRACE_FUN(ft_t_any);
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#if defined(__x86_64__)
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ps_per_cycle = 1000000000UL / cpu_khz;
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#elif defined(__alpha__)
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extern struct hwrpb_struct *hwrpb;
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ps_per_cycle = (1000*1000*1000*1000UL) / hwrpb->cycle_freq;
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#endif
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TRACE_EXIT;
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}
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/*
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* Input: function taking int count as parameter.
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* pointers to calculated calibration variables.
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*/
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void ftape_calibrate(char *name,
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void (*fun) (unsigned int),
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unsigned int *calibr_count,
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unsigned int *calibr_time)
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{
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static int first_time = 1;
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int i;
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unsigned int tc = 0;
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unsigned int count;
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unsigned int time;
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#if defined(__i386__)
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unsigned int old_tc = 0;
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unsigned int old_count = 1;
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unsigned int old_time = 1;
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#endif
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TRACE_FUN(ft_t_flow);
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if (first_time) { /* get idea of I/O performance */
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init_clock();
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time_inb();
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first_time = 0;
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}
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/* value of timeout must be set so that on very slow systems
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* it will give a time less than one jiffy, and on
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* very fast systems it'll give reasonable precision.
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*/
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count = 40;
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for (i = 0; i < 15; ++i) {
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unsigned int t0;
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unsigned int t1;
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unsigned int once;
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unsigned int multiple;
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unsigned long flags;
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*calibr_count =
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*calibr_time = count; /* set TC to 1 */
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spin_lock_irqsave(&calibr_lock, flags);
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fun(0); /* dummy, get code into cache */
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t0 = short_ftape_timestamp();
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fun(0); /* overhead + one test */
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t1 = short_ftape_timestamp();
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once = diff(t0, t1);
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t0 = short_ftape_timestamp();
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fun(count); /* overhead + count tests */
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t1 = short_ftape_timestamp();
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multiple = diff(t0, t1);
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spin_unlock_irqrestore(&calibr_lock, flags);
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time = ftape_timediff(0, multiple - once);
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tc = (1000 * time) / (count - 1);
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TRACE(ft_t_any, "once:%3d us,%6d times:%6d us, TC:%5d ns",
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usecs(once), count - 1, usecs(multiple), tc);
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#if defined(__alpha__) || defined(__x86_64__)
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/*
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* Increase the calibration count exponentially until the
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* calibration time exceeds 100 ms.
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*/
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if (time >= 100*1000) {
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break;
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}
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#elif defined(__i386__)
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/*
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* increase the count until the resulting time nears 2/HZ,
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* then the tc will drop sharply because we lose LATCH counts.
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*/
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if (tc <= old_tc / 2) {
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time = old_time;
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count = old_count;
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break;
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}
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old_tc = tc;
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old_count = count;
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old_time = time;
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#endif
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count *= 2;
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}
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*calibr_count = count - 1;
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*calibr_time = time;
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TRACE(ft_t_info, "TC for `%s()' = %d nsec (at %d counts)",
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name, (1000 * *calibr_time) / *calibr_count, *calibr_count);
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TRACE_EXIT;
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}
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