FreeBSD/Linux Kernel Cross Reference
sys/x86/isa/elcr.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2004 John Baldwin <jhb@FreeBSD.org>
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    /*
     * The ELCR is a register that controls the trigger mode and polarity of
     * EISA and ISA interrupts.  In FreeBSD 3.x and 4.x, the ELCR was only
     * consulted for determining the appropriate trigger mode of EISA
     * interrupts when using an APIC.  However, it seems that almost all
     * systems that include PCI also include an ELCR that manages the ISA
     * IRQs 0 through 15.  Thus, we check for the presence of an ELCR on
     * every machine by checking to see if the values found at bootup are
     * sane.  Note that the polarity of ISA and EISA IRQs are linked to the
     * trigger mode.  All edge triggered IRQs use active-hi polarity, and
     * all level triggered interrupts use active-lo polarity.
     *
     * The format of the ELCR is simple: it is a 16-bit bitmap where bit 0
     * controls IRQ 0, bit 1 controls IRQ 1, etc.  If the bit is zero, the
     * associated IRQ is edge triggered.  If the bit is one, the IRQ is
     * level triggered.
     */
    
    #include <sys/param.h>
    #include <sys/bus.h>
    #include <sys/systm.h>
    #include <machine/intr_machdep.h>
    
    #define ELCR_PORT       0x4d0
    #define ELCR_MASK(irq)  (1 << (irq))
    
    static int elcr_status;
    int elcr_found;
    
    /*
     * Check to see if we have what looks like a valid ELCR.  We do this by
     * verifying that IRQs 0, 1, 2, and 13 are all edge triggered.
     */
    int
    elcr_probe(void)
    {
            int i;
    
            elcr_status = inb(ELCR_PORT) | inb(ELCR_PORT + 1) << 8;
            if ((elcr_status & (ELCR_MASK(0) | ELCR_MASK(1) | ELCR_MASK(2) |
                ELCR_MASK(8) | ELCR_MASK(13))) != 0)
                    return (ENXIO);
            if (bootverbose) {
                    printf("ELCR Found.  ISA IRQs programmed as:\n");
                    for (i = 0; i < 16; i++)
                            printf(" %2d", i);
                    printf("\n");
                    for (i = 0; i < 16; i++)
                            if (elcr_status & ELCR_MASK(i))
                                    printf("  L");
                            else
                                    printf("  E");
                    printf("\n");
            }
            if (resource_disabled("elcr", 0))
                    return (ENXIO);
            elcr_found = 1;
            return (0);
    }
    
    /*
     * Returns 1 for level trigger, 0 for edge.
     */
    enum intr_trigger
    elcr_read_trigger(u_int irq)
    {
    
            KASSERT(elcr_found, ("%s: no ELCR was found!", __func__));
            KASSERT(irq <= 15, ("%s: invalid IRQ %u", __func__, irq));
           if (elcr_status & ELCR_MASK(irq))
                   return (INTR_TRIGGER_LEVEL);
           else
                   return (INTR_TRIGGER_EDGE);
   }
   
   /*
    * Set the trigger mode for a specified IRQ.  Mode of 0 means edge triggered,
    * and a mode of 1 means level triggered.
    */
   void
   elcr_write_trigger(u_int irq, enum intr_trigger trigger)
   {
           int new_status;
   
           KASSERT(elcr_found, ("%s: no ELCR was found!", __func__));
           KASSERT(irq <= 15, ("%s: invalid IRQ %u", __func__, irq));
           if (trigger == INTR_TRIGGER_LEVEL)
                   new_status = elcr_status | ELCR_MASK(irq);
           else
                   new_status = elcr_status & ~ELCR_MASK(irq);
           if (new_status == elcr_status)
                   return;
           elcr_status = new_status;
           if (irq >= 8)
                   outb(ELCR_PORT + 1, elcr_status >> 8);
           else
                   outb(ELCR_PORT, elcr_status & 0xff);
   }
   
   void
   elcr_resume(void)
   {
   
           KASSERT(elcr_found, ("%s: no ELCR was found!", __func__));
           outb(ELCR_PORT, elcr_status & 0xff);
           outb(ELCR_PORT + 1, elcr_status >> 8);
   }

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