Don't need old i8254 microtime() with timecounters.
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simonb
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/* $NetBSD: microtime.S,v 1.4 2005/12/11 12:17:41 christos Exp $ */
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/*-
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* Copyright (c) 1993 The Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <machine/asm.h>
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#include <dev/isa/isareg.h>
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#include <dev/ic/i8253reg.h>
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#include "assym.h"
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/* LINTSTUB: include <sys/time.h> */
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#define IRQ_BIT(irq_num) (1 << ((irq_num) % 8))
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#define IRQ_BYTE(irq_num) ((irq_num) >> 3)
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/* LINTSTUB: Func: void i8254_microtime(struct timeval *tv) */
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ENTRY(i8254_microtime)
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# clear registers and do whatever we can up front
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pushl %edi
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pushl %ebx
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xorl %edx,%edx
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movl $(TIMER_SEL0|TIMER_LATCH),%eax
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cli # disable interrupts
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# select timer 0 and latch its counter
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outb %al,$IO_TIMER1+TIMER_MODE
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inb $IO_ICU1,%al # as close to timer latch as possible
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movb %al,%ch # %ch is current ICU mask
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# Read counter value into [%al %dl], LSB first
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inb $IO_TIMER1+TIMER_CNTR0,%al
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movb %al,%dl # %dl has LSB
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inb $IO_TIMER1+TIMER_CNTR0,%al # %al has MSB
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/*
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* XXX this assumes that irq 0 is slot 0 on the primary CPU.
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* Currently always true, and not likely to change, but
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* still not a beauty.
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*/
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# save state of IIR in ICU, and of ipending, for later perusal
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movb CPUVAR(IPENDING) + IRQ_BYTE(0),%cl # %cl is interrupt pending
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# save the current value of _time
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movl _C_LABEL(time),%edi # get time.tv_sec
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movl _C_LABEL(time)+4,%ebx # and time.tv_usec
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sti # enable interrupts, we're done
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# At this point we've collected all the state we need to
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# compute the time. First figure out if we've got a pending
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# interrupt. If the IRQ0 bit is set in ipending we've taken
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# a clock interrupt without incrementing time, so we bump
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# time.tv_usec by a tick. Otherwise if the ICU shows a pending
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# interrupt for IRQ0 we (or the caller) may have blocked an interrupt
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# with the cli. If the counter is not a very small value (3 as
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# a heuristic), i.e. in pre-interrupt state, we add a tick to
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# time.tv_usec
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testb $IRQ_BIT(0),%cl # pending interrupt?
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jnz 1f # yes, increment count
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testb $IRQ_BIT(0),%ch # hardware interrupt pending?
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jz 2f # no, continue
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testb %al,%al # MSB zero?
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jnz 1f # no, add a tick
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cmpb $3,%dl # is this small number?
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jbe 2f # yes, continue
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1: addl _C_LABEL(isa_timer_tick),%ebx # add a tick
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# We've corrected for pending interrupts. Now do a table lookup
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# based on each of the high and low order counter bytes to increment
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# time.tv_usec
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2: movw _C_LABEL(isa_timer_msb_table)(,%eax,2),%ax
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subw _C_LABEL(isa_timer_lsb_table)(,%edx,2),%ax
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addl %eax,%ebx # add msb increment
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# Normalize the struct timeval. We know the previous increments
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# will be less than a second, so we'll only need to adjust accordingly
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cmpl $1000000,%ebx # carry in timeval?
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jb 3f
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subl $1000000,%ebx # adjust usec
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incl %edi # bump sec
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3: movl 12(%esp),%ecx # load timeval pointer arg
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movl %edi,(%ecx) # tvp->tv_sec = sec
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movl %ebx,4(%ecx) # tvp->tv_usec = usec
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popl %ebx
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popl %edi
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ret
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