The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/i386/isa/elcr.c

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    1 /*-
    2  * Copyright (c) 2004 John Baldwin <jhb@FreeBSD.org>
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  * 3. Neither the name of the author nor the names of any co-contributors
   14  *    may be used to endorse or promote products derived from this software
   15  *    without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  */
   29 
   30 #include <sys/cdefs.h>
   31 __FBSDID("$FreeBSD: releng/6.3/sys/i386/isa/elcr.c 140451 2005-01-18 20:24:47Z jhb $");
   32 
   33 /*
   34  * The ELCR is a register that controls the trigger mode and polarity of
   35  * EISA and ISA interrupts.  In FreeBSD 3.x and 4.x, the ELCR was only
   36  * consulted for determining the appropriate trigger mode of EISA
   37  * interrupts when using an APIC.  However, it seems that almost all
   38  * systems that include PCI also include an ELCR that manages the ISA
   39  * IRQs 0 through 15.  Thus, we check for the presence of an ELCR on
   40  * every machine by checking to see if the values found at bootup are
   41  * sane.  Note that the polarity of ISA and EISA IRQs are linked to the
   42  * trigger mode.  All edge triggered IRQs use active-hi polarity, and
   43  * all level triggered interrupts use active-lo polarity.
   44  *
   45  * The format of the ELCR is simple: it is a 16-bit bitmap where bit 0
   46  * controls IRQ 0, bit 1 controls IRQ 1, etc.  If the bit is zero, the
   47  * associated IRQ is edge triggered.  If the bit is one, the IRQ is
   48  * level triggered.
   49  */
   50 
   51 #include <sys/param.h>
   52 #include <sys/bus.h>
   53 #include <sys/systm.h>
   54 #include <machine/intr_machdep.h>
   55 
   56 #define ELCR_PORT       0x4d0
   57 #define ELCR_MASK(irq)  (1 << (irq))
   58 
   59 static int elcr_status;
   60 int elcr_found;
   61 
   62 /*
   63  * Check to see if we have what looks like a valid ELCR.  We do this by
   64  * verifying that IRQs 0, 1, 2, and 13 are all edge triggered.
   65  */
   66 int
   67 elcr_probe(void)
   68 {
   69         int i;
   70 
   71         elcr_status = inb(ELCR_PORT) | inb(ELCR_PORT + 1) << 8;
   72         if ((elcr_status & (ELCR_MASK(0) | ELCR_MASK(1) | ELCR_MASK(2) |
   73             ELCR_MASK(8) | ELCR_MASK(13))) != 0)
   74                 return (ENXIO);
   75         if (bootverbose) {
   76                 printf("ELCR Found.  ISA IRQs programmed as:\n");
   77                 for (i = 0; i < 16; i++)
   78                         printf(" %2d", i);
   79                 printf("\n");
   80                 for (i = 0; i < 16; i++)
   81                         if (elcr_status & ELCR_MASK(i))
   82                                 printf("  L");
   83                         else
   84                                 printf("  E");
   85                 printf("\n");
   86         }
   87         if (resource_disabled("elcr", 0))
   88                 return (ENXIO);
   89         elcr_found = 1;
   90         return (0);
   91 }
   92 
   93 /*
   94  * Returns 1 for level trigger, 0 for edge.
   95  */
   96 enum intr_trigger
   97 elcr_read_trigger(u_int irq)
   98 {
   99 
  100         KASSERT(elcr_found, ("%s: no ELCR was found!", __func__));
  101         KASSERT(irq <= 15, ("%s: invalid IRQ %u", __func__, irq));
  102         if (elcr_status & ELCR_MASK(irq))
  103                 return (INTR_TRIGGER_LEVEL);
  104         else
  105                 return (INTR_TRIGGER_EDGE);
  106 }
  107 
  108 /*
  109  * Set the trigger mode for a specified IRQ.  Mode of 0 means edge triggered,
  110  * and a mode of 1 means level triggered.
  111  */
  112 void
  113 elcr_write_trigger(u_int irq, enum intr_trigger trigger)
  114 {
  115         int new_status;
  116 
  117         KASSERT(elcr_found, ("%s: no ELCR was found!", __func__));
  118         KASSERT(irq <= 15, ("%s: invalid IRQ %u", __func__, irq));
  119         if (trigger == INTR_TRIGGER_LEVEL)
  120                 new_status = elcr_status | ELCR_MASK(irq);
  121         else
  122                 new_status = elcr_status & ~ELCR_MASK(irq);
  123         if (new_status == elcr_status)
  124                 return;
  125         elcr_status = new_status;
  126         if (irq >= 8)
  127                 outb(ELCR_PORT + 1, elcr_status >> 8);
  128         else
  129                 outb(ELCR_PORT, elcr_status & 0xff);
  130 }
  131 
  132 void
  133 elcr_resume(void)
  134 {
  135 
  136         KASSERT(elcr_found, ("%s: no ELCR was found!", __func__));
  137         outb(ELCR_PORT, elcr_status & 0xff);
  138         outb(ELCR_PORT + 1, elcr_status >> 8);
  139 }

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