/*-
 * Copyright (c) 2002 Mitsuru IWASAKI <iwasaki@jp.freebsd.org>
 * All rights reserved.
 *
 * 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>
#include "opt_acpi.h"
#include <sys/param.h>
#include <sys/bus.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/malloc.h>
#include <sys/module.h>

#include <contrib/dev/acpica/include/acpi.h>

#include <dev/acpica/acpivar.h>
#include <dev/acpica/acpi_pcibvar.h>

#include <machine/pci_cfgreg.h>
#include <dev/pci/pcireg.h>
#include <dev/pci/pcivar.h>
#include "pcib_if.h"

/* Hooks for the ACPI CA debugging infrastructure. */
#define _COMPONENT      ACPI_BUS
ACPI_MODULE_NAME("PCI_LINK")

ACPI_SERIAL_DECL(pci_link, "ACPI PCI link");

#define NUM_ISA_INTERRUPTS      16
#define NUM_ACPI_INTERRUPTS     256

/*
 * An ACPI PCI link device may contain multiple links.  Each link has its
 * own ACPI resource.  _PRT entries specify which link is being used via
 * the Source Index.
 *
 * XXX: A note about Source Indices and DPFs:  Currently we assume that
 * the DPF start and end tags are not counted towards the index that
 * Source Index corresponds to.  Also, we assume that when DPFs are in use
 * they various sets overlap in terms of Indices.  Here's an example
 * resource list indicating these assumptions:
 *
 * Resource             Index
 * --------             -----
 * I/O Port             0
 * Start DPF            -
 * IRQ                  1
 * MemIO                2
 * Start DPF            -
 * IRQ                  1
 * MemIO                2
 * End DPF              -
 * DMA Channel          3
 *
 * The XXX is because I'm not sure if this is a valid assumption to make.
 */

/* States during DPF processing. */
#define DPF_OUTSIDE     0
#define DPF_FIRST       1
#define DPF_IGNORE      2

struct link;

struct acpi_pci_link_softc {
        int     pl_num_links;
        int     pl_crs_bad;
        struct link *pl_links;
        device_t pl_dev;
};

struct link {
        struct acpi_pci_link_softc *l_sc;
        uint8_t l_bios_irq;
        uint8_t l_irq;
        uint8_t l_initial_irq;
        UINT32  l_crs_type;
        int     l_res_index;
        int     l_num_irqs;
        int     *l_irqs;
        int     l_references;
        bool    l_routed:1;
        bool    l_isa_irq:1;
        ACPI_RESOURCE l_prs_template;
};

struct link_count_request {
        int     in_dpf;
        int     count;
};

struct link_res_request {
        struct acpi_pci_link_softc *sc;
        int     in_dpf;
        int     res_index;
        int     link_index;
};

static MALLOC_DEFINE(M_PCI_LINK, "pci_link", "ACPI PCI Link structures");

static int pci_link_interrupt_weights[NUM_ACPI_INTERRUPTS];
static int pci_link_bios_isa_irqs;

static char *pci_link_ids[] = { "PNP0C0F", NULL };

/*
 * Fetch the short name associated with an ACPI handle and save it in the
 * passed in buffer.
 */
static ACPI_STATUS
acpi_short_name(ACPI_HANDLE handle, char *buffer, size_t buflen)
{
        ACPI_BUFFER buf;

        buf.Length = buflen;
        buf.Pointer = buffer;
        return (AcpiGetName(handle, ACPI_SINGLE_NAME, &buf));
}

static int
acpi_pci_link_probe(device_t dev)
{
        char name[12];
        int rv;

        /*
         * We explicitly do not check _STA since not all systems set it to
         * sensible values.
         */
        if (acpi_disabled("pci_link"))
            return (ENXIO);
        rv = ACPI_ID_PROBE(device_get_parent(dev), dev, pci_link_ids, NULL);
        if (rv > 0)
          return (rv);

        if (ACPI_SUCCESS(acpi_short_name(acpi_get_handle(dev), name,
            sizeof(name))))
                device_set_descf(dev, "ACPI PCI Link %s", name);
        else
                device_set_desc(dev, "ACPI PCI Link");
        device_quiet(dev);
        return (rv);
}

static ACPI_STATUS
acpi_count_irq_resources(ACPI_RESOURCE *res, void *context)
{
        struct link_count_request *req;

        req = (struct link_count_request *)context;
        switch (res->Type) {
        case ACPI_RESOURCE_TYPE_START_DEPENDENT:
                switch (req->in_dpf) {
                case DPF_OUTSIDE:
                        /* We've started the first DPF. */
                        req->in_dpf = DPF_FIRST;
                        break;
                case DPF_FIRST:
                        /* We've started the second DPF. */
                        req->in_dpf = DPF_IGNORE;
                        break;
                }
                break;
        case ACPI_RESOURCE_TYPE_END_DEPENDENT:
                /* We are finished with DPF parsing. */
                KASSERT(req->in_dpf != DPF_OUTSIDE,
                    ("%s: end dpf when not parsing a dpf", __func__));
                req->in_dpf = DPF_OUTSIDE;
                break;
        case ACPI_RESOURCE_TYPE_IRQ:
        case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
                /*
                 * Don't count resources if we are in a DPF set that we are
                 * ignoring.
                 */
                if (req->in_dpf != DPF_IGNORE)
                        req->count++;
        }
        return (AE_OK);
}

static ACPI_STATUS
link_add_crs(ACPI_RESOURCE *res, void *context)
{
        struct link_res_request *req;
        struct link *link;

        ACPI_SERIAL_ASSERT(pci_link);
        req = (struct link_res_request *)context;
        switch (res->Type) {
        case ACPI_RESOURCE_TYPE_START_DEPENDENT:
                switch (req->in_dpf) {
                case DPF_OUTSIDE:
                        /* We've started the first DPF. */
                        req->in_dpf = DPF_FIRST;
                        break;
                case DPF_FIRST:
                        /* We've started the second DPF. */
                        panic(
                "%s: Multiple dependent functions within a current resource",
                            __func__);
                        break;
                }
                break;
        case ACPI_RESOURCE_TYPE_END_DEPENDENT:
                /* We are finished with DPF parsing. */
                KASSERT(req->in_dpf != DPF_OUTSIDE,
                    ("%s: end dpf when not parsing a dpf", __func__));
                req->in_dpf = DPF_OUTSIDE;
                break;
        case ACPI_RESOURCE_TYPE_IRQ:
        case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
                KASSERT(req->link_index < req->sc->pl_num_links,
                    ("%s: array boundary violation", __func__));
                link = &req->sc->pl_links[req->link_index];
                link->l_res_index = req->res_index;
                link->l_crs_type = res->Type;
                req->link_index++;
                req->res_index++;

                /*
                 * Only use the current value if there's one IRQ.  Some
                 * systems return multiple IRQs (which is nonsense for _CRS)
                 * when the link hasn't been programmed.
                 */
                if (res->Type == ACPI_RESOURCE_TYPE_IRQ) {
                        if (res->Data.Irq.InterruptCount == 1)
                                link->l_irq = res->Data.Irq.Interrupts[0];
                } else if (res->Data.ExtendedIrq.InterruptCount == 1)
                        link->l_irq = res->Data.ExtendedIrq.Interrupts[0];

                /*
                 * An IRQ of zero means that the link isn't routed.
                 */
                if (link->l_irq == 0)
                        link->l_irq = PCI_INVALID_IRQ;
                break;
        default:
                req->res_index++;
        }
        return (AE_OK);
}

/*
 * Populate the set of possible IRQs for each device.
 */
static ACPI_STATUS
link_add_prs(ACPI_RESOURCE *res, void *context)
{
        ACPI_RESOURCE *tmp;
        struct link_res_request *req;
        struct link *link;
        UINT8 *irqs = NULL;
        UINT32 *ext_irqs = NULL;
        int i, is_ext_irq = 1;

        ACPI_SERIAL_ASSERT(pci_link);
        req = (struct link_res_request *)context;
        switch (res->Type) {
        case ACPI_RESOURCE_TYPE_START_DEPENDENT:
                switch (req->in_dpf) {
                case DPF_OUTSIDE:
                        /* We've started the first DPF. */
                        req->in_dpf = DPF_FIRST;
                        break;
                case DPF_FIRST:
                        /* We've started the second DPF. */
                        req->in_dpf = DPF_IGNORE;
                        break;
                }
                break;
        case ACPI_RESOURCE_TYPE_END_DEPENDENT:
                /* We are finished with DPF parsing. */
                KASSERT(req->in_dpf != DPF_OUTSIDE,
                    ("%s: end dpf when not parsing a dpf", __func__));
                req->in_dpf = DPF_OUTSIDE;
                break;
        case ACPI_RESOURCE_TYPE_IRQ:
                is_ext_irq = 0;
                /* fall through */
        case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
                /*
                 * Don't parse resources if we are in a DPF set that we are
                 * ignoring.
                 */
                if (req->in_dpf == DPF_IGNORE)
                        break;

                KASSERT(req->link_index < req->sc->pl_num_links,
                    ("%s: array boundary violation", __func__));
                link = &req->sc->pl_links[req->link_index];
                if (link->l_res_index == -1) {
                        KASSERT(req->sc->pl_crs_bad,
                            ("res_index should be set"));
                        link->l_res_index = req->res_index;
                }
                req->link_index++;
                req->res_index++;

                /*
                 * Stash a copy of the resource for later use when doing
                 * _SRS.
                 */
                tmp = &link->l_prs_template;
                if (is_ext_irq) {
                        bcopy(res, tmp, ACPI_RS_SIZE(tmp->Data.ExtendedIrq));

                        /*
                         * XXX acpi_AppendBufferResource() cannot handle
                         * optional data.
                         */
                        bzero(&tmp->Data.ExtendedIrq.ResourceSource,
                            sizeof(tmp->Data.ExtendedIrq.ResourceSource));
                        tmp->Length = ACPI_RS_SIZE(tmp->Data.ExtendedIrq);

                        link->l_num_irqs =
                            res->Data.ExtendedIrq.InterruptCount;
                        ext_irqs = res->Data.ExtendedIrq.Interrupts;
                } else {
                        bcopy(res, tmp, ACPI_RS_SIZE(tmp->Data.Irq));
                        link->l_num_irqs = res->Data.Irq.InterruptCount;
                        irqs = res->Data.Irq.Interrupts;
                }
                if (link->l_num_irqs == 0)
                        break;

                /*
                 * Save a list of the valid IRQs.  Also, if all of the
                 * valid IRQs are ISA IRQs, then mark this link as
                 * routed via an ISA interrupt.
                 */
                link->l_isa_irq = true;
                link->l_irqs = malloc(sizeof(int) * link->l_num_irqs,
                    M_PCI_LINK, M_WAITOK | M_ZERO);
                for (i = 0; i < link->l_num_irqs; i++) {
                        if (is_ext_irq) {
                                link->l_irqs[i] = ext_irqs[i];
                                if (ext_irqs[i] >= NUM_ISA_INTERRUPTS)
                                        link->l_isa_irq = false;
                        } else {
                                link->l_irqs[i] = irqs[i];
                                if (irqs[i] >= NUM_ISA_INTERRUPTS)
                                        link->l_isa_irq = false;
                        }
                }

                /*
                 * If this is not an ISA IRQ but _CRS used a non-extended
                 * IRQ descriptor, don't use _CRS as a template for _SRS.
                 */
                if (!req->sc->pl_crs_bad && !link->l_isa_irq &&
                    link->l_crs_type == ACPI_RESOURCE_TYPE_IRQ)
                        req->sc->pl_crs_bad = true;
                break;
        default:
                if (req->in_dpf == DPF_IGNORE)
                        break;
                if (req->sc->pl_crs_bad)
                        device_printf(req->sc->pl_dev,
                    "Warning: possible resource %d will be lost during _SRS\n",
                            req->res_index);
                req->res_index++;
        }
        return (AE_OK);
}

static bool
link_valid_irq(struct link *link, int irq)
{
        int i;

        ACPI_SERIAL_ASSERT(pci_link);

        /* Invalid interrupts are never valid. */
        if (!PCI_INTERRUPT_VALID(irq))
                return (false);

        /* Any interrupt in the list of possible interrupts is valid. */
        for (i = 0; i < link->l_num_irqs; i++)
                if (link->l_irqs[i] == irq)
                         return (true);

        /*
         * For links routed via an ISA interrupt, if the SCI is routed via
         * an ISA interrupt, the SCI is always treated as a valid IRQ.
         */
        if (link->l_isa_irq && AcpiGbl_FADT.SciInterrupt == irq &&
            irq < NUM_ISA_INTERRUPTS)
                return (true);

        /* If the interrupt wasn't found in the list it is not valid. */
        return (false);
}

static void
acpi_pci_link_dump(struct acpi_pci_link_softc *sc, int header, const char *tag)
{
        struct link *link;
        char buf[16];
        int i, j;

        ACPI_SERIAL_ASSERT(pci_link);
        if (header) {
                snprintf(buf, sizeof(buf), "%s:",
                    device_get_nameunit(sc->pl_dev));
                printf("%-16.16s  Index  IRQ  Rtd  Ref  IRQs\n", buf);
        }
        for (i = 0; i < sc->pl_num_links; i++) {
                link = &sc->pl_links[i];
                printf("  %-14.14s  %5d  %3d   %c   %3d ", i == 0 ? tag : "", i,
                    link->l_irq, link->l_routed ? 'Y' : 'N',
                    link->l_references);
                if (link->l_num_irqs == 0)
                        printf(" none");
                else for (j = 0; j < link->l_num_irqs; j++)
                        printf(" %d", link->l_irqs[j]);
                printf("\n");
        }
}

static int
acpi_pci_link_attach(device_t dev)
{
        struct acpi_pci_link_softc *sc;
        struct link_count_request creq;
        struct link_res_request rreq;
        ACPI_STATUS status;
        int i;

        sc = device_get_softc(dev);
        sc->pl_dev = dev;
        ACPI_SERIAL_BEGIN(pci_link);

        /*
         * Count the number of current resources so we know how big of
         * a link array to allocate.  On some systems, _CRS is broken,
         * so for those systems try to derive the count from _PRS instead.
         */
        creq.in_dpf = DPF_OUTSIDE;
        creq.count = 0;
        status = AcpiWalkResources(acpi_get_handle(dev), "_CRS",
            acpi_count_irq_resources, &creq);
        sc->pl_crs_bad = ACPI_FAILURE(status);
        if (sc->pl_crs_bad) {
                creq.in_dpf = DPF_OUTSIDE;
                creq.count = 0;
                status = AcpiWalkResources(acpi_get_handle(dev), "_PRS",
                    acpi_count_irq_resources, &creq);
                if (ACPI_FAILURE(status)) {
                        device_printf(dev,
                            "Unable to parse _CRS or _PRS: %s\n",
                            AcpiFormatException(status));
                        ACPI_SERIAL_END(pci_link);
                        return (ENXIO);
                }
        }
        sc->pl_num_links = creq.count;
        if (creq.count == 0) {
                ACPI_SERIAL_END(pci_link);
                return (0);
        }
        sc->pl_links = malloc(sizeof(struct link) * sc->pl_num_links,
            M_PCI_LINK, M_WAITOK | M_ZERO);

        /* Initialize the child links. */
        for (i = 0; i < sc->pl_num_links; i++) {
                sc->pl_links[i].l_irq = PCI_INVALID_IRQ;
                sc->pl_links[i].l_bios_irq = PCI_INVALID_IRQ;
                sc->pl_links[i].l_sc = sc;
                sc->pl_links[i].l_isa_irq = false;
                sc->pl_links[i].l_res_index = -1;
        }

        /* Try to read the current settings from _CRS if it is valid. */
        if (!sc->pl_crs_bad) {
                rreq.in_dpf = DPF_OUTSIDE;
                rreq.link_index = 0;
                rreq.res_index = 0;
                rreq.sc = sc;
                status = AcpiWalkResources(acpi_get_handle(dev), "_CRS",
                    link_add_crs, &rreq);
                if (ACPI_FAILURE(status)) {
                        device_printf(dev, "Unable to parse _CRS: %s\n",
                            AcpiFormatException(status));
                        goto fail;
                }
        }

        /*
         * Try to read the possible settings from _PRS.  Note that if the
         * _CRS is toast, we depend on having a working _PRS.  However, if
         * _CRS works, then it is ok for _PRS to be missing.
         */
        rreq.in_dpf = DPF_OUTSIDE;
        rreq.link_index = 0;
        rreq.res_index = 0;
        rreq.sc = sc;
        status = AcpiWalkResources(acpi_get_handle(dev), "_PRS",
            link_add_prs, &rreq);
        if (ACPI_FAILURE(status) &&
            (status != AE_NOT_FOUND || sc->pl_crs_bad)) {
                device_printf(dev, "Unable to parse _PRS: %s\n",
                    AcpiFormatException(status));
                goto fail;
        }
        if (bootverbose)
                acpi_pci_link_dump(sc, 1, "Initial Probe");

        /* Verify initial IRQs if we have _PRS. */
        if (status != AE_NOT_FOUND)
                for (i = 0; i < sc->pl_num_links; i++)
                        if (!link_valid_irq(&sc->pl_links[i],
                            sc->pl_links[i].l_irq))
                                sc->pl_links[i].l_irq = PCI_INVALID_IRQ;
        if (bootverbose)
                acpi_pci_link_dump(sc, 0, "Validation");

        /* Save initial IRQs. */
        for (i = 0; i < sc->pl_num_links; i++)
                sc->pl_links[i].l_initial_irq = sc->pl_links[i].l_irq;

        /*
         * Try to disable this link.  If successful, set the current IRQ to
         * zero and flags to indicate this link is not routed.  If we can't
         * run _DIS (i.e., the method doesn't exist), assume the initial
         * IRQ was routed by the BIOS.
         */
        if (ACPI_SUCCESS(AcpiEvaluateObject(acpi_get_handle(dev), "_DIS", NULL,
            NULL)))
                for (i = 0; i < sc->pl_num_links; i++)
                        sc->pl_links[i].l_irq = PCI_INVALID_IRQ;
        else
                for (i = 0; i < sc->pl_num_links; i++)
                        if (PCI_INTERRUPT_VALID(sc->pl_links[i].l_irq))
                                sc->pl_links[i].l_routed = true;
        if (bootverbose)
                acpi_pci_link_dump(sc, 0, "After Disable");
        ACPI_SERIAL_END(pci_link);
        return (0);
fail:
        ACPI_SERIAL_END(pci_link);
        for (i = 0; i < sc->pl_num_links; i++)
                if (sc->pl_links[i].l_irqs != NULL)
                        free(sc->pl_links[i].l_irqs, M_PCI_LINK);
        free(sc->pl_links, M_PCI_LINK);
        return (ENXIO);
}

/* XXX: Note that this is identical to pci_pir_search_irq(). */
static uint8_t
acpi_pci_link_search_irq(int domain, int bus, int device, int pin)
{
        uint32_t value;
        uint8_t func, maxfunc;

        /* See if we have a valid device at function 0. */
        value = pci_cfgregread(domain, bus, device, 0, PCIR_VENDOR, 2);
        if (value == PCIV_INVALID)
                return (PCI_INVALID_IRQ);
        value = pci_cfgregread(domain, bus, device, 0, PCIR_HDRTYPE, 1);
        if ((value & PCIM_HDRTYPE) > PCI_MAXHDRTYPE)
                return (PCI_INVALID_IRQ);
        if (value & PCIM_MFDEV)
                maxfunc = PCI_FUNCMAX;
        else
                maxfunc = 0;

        /* Scan all possible functions at this device. */
        for (func = 0; func <= maxfunc; func++) {
                value = pci_cfgregread(domain, bus, device, func, PCIR_VENDOR,
                    2);
                if (value == PCIV_INVALID)
                        continue;
                value = pci_cfgregread(domain, bus, device, func, PCIR_INTPIN,
                    1);

                /*
                 * See if it uses the pin in question.  Note that the passed
                 * in pin uses 0 for A, .. 3 for D whereas the intpin
                 * register uses 0 for no interrupt, 1 for A, .. 4 for D.
                 */
                if (value != pin + 1)
                        continue;
                value = pci_cfgregread(domain, bus, device, func, PCIR_INTLINE,
                    1);
                if (bootverbose)
                        printf(
                "ACPI: Found matching pin for %d.%d.INT%c at func %d: %d\n",
                            bus, device, pin + 'A', func, value);
                if (value != PCI_INVALID_IRQ)
                        return (value);
        }
        return (PCI_INVALID_IRQ);
}

/*
 * Find the link structure that corresponds to the resource index passed in
 * via 'source_index'.
 */
static struct link *
acpi_pci_link_lookup(device_t dev, int source_index)
{
        struct acpi_pci_link_softc *sc;
        int i;

        ACPI_SERIAL_ASSERT(pci_link);
        sc = device_get_softc(dev);
        for (i = 0; i < sc->pl_num_links; i++)
                if (sc->pl_links[i].l_res_index == source_index)
                        return (&sc->pl_links[i]);
        return (NULL);
}

void
acpi_pci_link_add_reference(device_t dev, int index, device_t pcib, int slot,
    int pin)
{
        struct link *link;
        uint8_t bios_irq;
        uintptr_t bus, domain;

        /*
         * Look up the PCI domain and bus for the specified PCI bridge
         * device.  Note that the PCI bridge device might not have any
         * children yet.  However, looking up these IVARs doesn't
         * require a valid child device, so we just pass NULL.
         */
        if (BUS_READ_IVAR(pcib, NULL, PCIB_IVAR_BUS, &bus) != 0) {
                device_printf(pcib, "Unable to read PCI bus number");
                panic("PCI bridge without a bus number");
        }
        if (BUS_READ_IVAR(pcib, NULL, PCIB_IVAR_DOMAIN, &domain) != 0) {
                device_printf(pcib, "Unable to read PCI domain number");
                panic("PCI bridge without a domain number");
        }
                
        /* Bump the reference count. */
        ACPI_SERIAL_BEGIN(pci_link);
        link = acpi_pci_link_lookup(dev, index);
        if (link == NULL) {
                device_printf(dev, "apparently invalid index %d\n", index);
                ACPI_SERIAL_END(pci_link);
                return;
        }
        link->l_references++;
        if (link->l_routed)
                pci_link_interrupt_weights[link->l_irq]++;

        /*
         * The BIOS only routes interrupts via ISA IRQs using the ATPICs
         * (8259As).  Thus, if this link is routed via an ISA IRQ, go
         * look to see if the BIOS routed an IRQ for this link at the
         * indicated (domain, bus, slot, pin).  If so, we prefer that IRQ for
         * this link and add that IRQ to our list of known-good IRQs.
         * This provides a good work-around for link devices whose _CRS
         * method is either broken or bogus.  We only use the value
         * returned by _CRS if we can't find a valid IRQ via this method
         * in fact.
         *
         * If this link is not routed via an ISA IRQ (because we are using
         * APIC for example), then don't bother looking up the BIOS IRQ
         * as if we find one it won't be valid anyway.
         */
        if (!link->l_isa_irq) {
                ACPI_SERIAL_END(pci_link);
                return;
        }

        /* Try to find a BIOS IRQ setting from any matching devices. */
        bios_irq = acpi_pci_link_search_irq(domain, bus, slot, pin);
        if (!PCI_INTERRUPT_VALID(bios_irq)) {
                ACPI_SERIAL_END(pci_link);
                return;
        }

        /* Validate the BIOS IRQ. */
        if (!link_valid_irq(link, bios_irq)) {
                device_printf(dev, "BIOS IRQ %u for %d.%d.INT%c is invalid\n",
                    bios_irq, (int)bus, slot, pin + 'A');
        } else if (!PCI_INTERRUPT_VALID(link->l_bios_irq)) {
                link->l_bios_irq = bios_irq;
                if (bios_irq < NUM_ISA_INTERRUPTS)
                        pci_link_bios_isa_irqs |= (1 << bios_irq);
                if (bios_irq != link->l_initial_irq &&
                    PCI_INTERRUPT_VALID(link->l_initial_irq))
                        device_printf(dev,
                            "BIOS IRQ %u does not match initial IRQ %u\n",
                            bios_irq, link->l_initial_irq);
        } else if (bios_irq != link->l_bios_irq)
                device_printf(dev,
            "BIOS IRQ %u for %d.%d.INT%c does not match previous BIOS IRQ %u\n",
                    bios_irq, (int)bus, slot, pin + 'A',
                    link->l_bios_irq);
        ACPI_SERIAL_END(pci_link);
}

static ACPI_STATUS
acpi_pci_link_srs_from_crs(struct acpi_pci_link_softc *sc, ACPI_BUFFER *srsbuf)
{
        ACPI_RESOURCE *end, *res;
        ACPI_STATUS status;
        struct link *link;
        int i __diagused, in_dpf;

        /* Fetch the _CRS. */
        ACPI_SERIAL_ASSERT(pci_link);
        srsbuf->Pointer = NULL;
        srsbuf->Length = ACPI_ALLOCATE_BUFFER;
        status = AcpiGetCurrentResources(acpi_get_handle(sc->pl_dev), srsbuf);
        if (ACPI_SUCCESS(status) && srsbuf->Pointer == NULL)
                status = AE_NO_MEMORY;
        if (ACPI_FAILURE(status)) {
                if (bootverbose)
                        device_printf(sc->pl_dev,
                            "Unable to fetch current resources: %s\n",
                            AcpiFormatException(status));
                return (status);
        }

        /* Fill in IRQ resources via link structures. */
        link = sc->pl_links;
        i = 0;
        in_dpf = DPF_OUTSIDE;
        res = (ACPI_RESOURCE *)srsbuf->Pointer;
        end = (ACPI_RESOURCE *)((char *)srsbuf->Pointer + srsbuf->Length);
        for (;;) {
                switch (res->Type) {
                case ACPI_RESOURCE_TYPE_START_DEPENDENT:
                        switch (in_dpf) {
                        case DPF_OUTSIDE:
                                /* We've started the first DPF. */
                                in_dpf = DPF_FIRST;
                                break;
                        case DPF_FIRST:
                                /* We've started the second DPF. */
                                panic(
                "%s: Multiple dependent functions within a current resource",
                                    __func__);
                                break;
                        }
                        break;
                case ACPI_RESOURCE_TYPE_END_DEPENDENT:
                        /* We are finished with DPF parsing. */
                        KASSERT(in_dpf != DPF_OUTSIDE,
                            ("%s: end dpf when not parsing a dpf", __func__));
                        in_dpf = DPF_OUTSIDE;
                        break;
                case ACPI_RESOURCE_TYPE_IRQ:
                        MPASS(i < sc->pl_num_links);
                        res->Data.Irq.InterruptCount = 1;
                        if (PCI_INTERRUPT_VALID(link->l_irq)) {
                                KASSERT(link->l_irq < NUM_ISA_INTERRUPTS,
                ("%s: can't put non-ISA IRQ %d in legacy IRQ resource type",
                                    __func__, link->l_irq));
                                res->Data.Irq.Interrupts[0] = link->l_irq;
                        } else
                                res->Data.Irq.Interrupts[0] = 0;
                        link++;
                        i++;
                        break;
                case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
                        MPASS(i < sc->pl_num_links);
                        res->Data.ExtendedIrq.InterruptCount = 1;
                        if (PCI_INTERRUPT_VALID(link->l_irq))
                                res->Data.ExtendedIrq.Interrupts[0] =
                                    link->l_irq;
                        else
                                res->Data.ExtendedIrq.Interrupts[0] = 0;
                        link++;
                        i++;
                        break;
                }
                if (res->Type == ACPI_RESOURCE_TYPE_END_TAG)
                        break;
                res = ACPI_NEXT_RESOURCE(res);
                if (res >= end)
                        break;
        }
        return (AE_OK);
}

static ACPI_STATUS
acpi_pci_link_srs_from_links(struct acpi_pci_link_softc *sc,
    ACPI_BUFFER *srsbuf)
{
        ACPI_RESOURCE newres;
        ACPI_STATUS status;
        struct link *link;
        int i;

        /* Start off with an empty buffer. */
        srsbuf->Pointer = NULL;
        link = sc->pl_links;
        for (i = 0; i < sc->pl_num_links; i++) {
                /* Add a new IRQ resource from each link. */
                link = &sc->pl_links[i];
                if (link->l_prs_template.Type == ACPI_RESOURCE_TYPE_IRQ) {
                        /* Build an IRQ resource. */
                        bcopy(&link->l_prs_template, &newres,
                            ACPI_RS_SIZE(newres.Data.Irq));
                        newres.Data.Irq.InterruptCount = 1;
                        if (PCI_INTERRUPT_VALID(link->l_irq)) {
                                KASSERT(link->l_irq < NUM_ISA_INTERRUPTS,
                ("%s: can't put non-ISA IRQ %d in legacy IRQ resource type",
                                    __func__, link->l_irq));
                                newres.Data.Irq.Interrupts[0] = link->l_irq;
                        } else
                                newres.Data.Irq.Interrupts[0] = 0;
                } else {
                        /* Build an ExtIRQ resuorce. */
                        bcopy(&link->l_prs_template, &newres,
                            ACPI_RS_SIZE(newres.Data.ExtendedIrq));
                        newres.Data.ExtendedIrq.InterruptCount = 1;
                        if (PCI_INTERRUPT_VALID(link->l_irq))
                                newres.Data.ExtendedIrq.Interrupts[0] =
                                    link->l_irq;
                        else
                                newres.Data.ExtendedIrq.Interrupts[0] = 0;
                }

                /* Add the new resource to the end of the _SRS buffer. */
                status = acpi_AppendBufferResource(srsbuf, &newres);
                if (ACPI_FAILURE(status)) {
                        device_printf(sc->pl_dev,
                            "Unable to build resources: %s\n",
                            AcpiFormatException(status));
                        if (srsbuf->Pointer != NULL) {
                                AcpiOsFree(srsbuf->Pointer);
                                srsbuf->Pointer = NULL;
                        }
                        return (status);
                }
        }
        return (AE_OK);
}

static ACPI_STATUS
acpi_pci_link_route_irqs(device_t dev)
{
        struct acpi_pci_link_softc *sc;
        ACPI_RESOURCE *resource, *end;
        ACPI_BUFFER srsbuf;
        ACPI_STATUS status;
        struct link *link;
        int i __diagused;

        ACPI_SERIAL_ASSERT(pci_link);
        sc = device_get_softc(dev);
        if (sc->pl_crs_bad)
                status = acpi_pci_link_srs_from_links(sc, &srsbuf);
        else
                status = acpi_pci_link_srs_from_crs(sc, &srsbuf);
        if (ACPI_FAILURE(status))
                return (status);

        /* Write out new resources via _SRS. */
        status = AcpiSetCurrentResources(acpi_get_handle(dev), &srsbuf);
        if (ACPI_FAILURE(status)) {
                device_printf(dev, "Unable to route IRQs: %s\n",
                    AcpiFormatException(status));
                AcpiOsFree(srsbuf.Pointer);
                return (status);
        }

        /*
         * Perform acpi_config_intr() on each IRQ resource if it was just
         * routed for the first time.
         */
        link = sc->pl_links;
        i = 0;
        resource = (ACPI_RESOURCE *)srsbuf.Pointer;
        end = (ACPI_RESOURCE *)((char *)srsbuf.Pointer + srsbuf.Length);
        for (;;) {
                if (resource->Type == ACPI_RESOURCE_TYPE_END_TAG)
                        break;
                switch (resource->Type) {
                case ACPI_RESOURCE_TYPE_IRQ:
                case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
                        MPASS(i < sc->pl_num_links);

                        /*
                         * Only configure the interrupt and update the
                         * weights if this link has a valid IRQ and was
                         * previously unrouted.
                         */
                        if (!link->l_routed &&
                            PCI_INTERRUPT_VALID(link->l_irq)) {
                                link->l_routed = true;
                                acpi_config_intr(dev, resource);
                                pci_link_interrupt_weights[link->l_irq] +=
                                    link->l_references;
                        }
                        link++;
                        i++;
                        break;
                }
                resource = ACPI_NEXT_RESOURCE(resource);
                if (resource >= end)
                        break;
        }
        AcpiOsFree(srsbuf.Pointer);
        return (AE_OK);
}

static int
acpi_pci_link_resume(device_t dev)
{
        struct acpi_pci_link_softc *sc;
        ACPI_STATUS status;
        int i, routed;

        /*
         * If all of our links are routed, then restore the link via _SRS,
         * otherwise, disable the link via _DIS.
         */
        ACPI_SERIAL_BEGIN(pci_link);
        sc = device_get_softc(dev);
        routed = 0;
        for (i = 0; i < sc->pl_num_links; i++)
                if (sc->pl_links[i].l_routed)
                        routed++;
        if (routed == sc->pl_num_links)
                status = acpi_pci_link_route_irqs(dev);
        else {
                AcpiEvaluateObject(acpi_get_handle(dev), "_DIS", NULL, NULL);
                status = AE_OK;
        }
        ACPI_SERIAL_END(pci_link);
        if (ACPI_FAILURE(status))
                return (ENXIO);
        else
                return (0);
}

/*
 * Pick an IRQ to use for this unrouted link.
 */
static uint8_t
acpi_pci_link_choose_irq(device_t dev, struct link *link)
{
        char tunable_buffer[64], link_name[5];
        u_int8_t best_irq, pos_irq;
        int best_weight, pos_weight, i;

        KASSERT(!link->l_routed, ("%s: link already routed", __func__));
        KASSERT(!PCI_INTERRUPT_VALID(link->l_irq),
            ("%s: link already has an IRQ", __func__));

        /* Check for a tunable override. */
        if (ACPI_SUCCESS(acpi_short_name(acpi_get_handle(dev), link_name,
            sizeof(link_name)))) {
                snprintf(tunable_buffer, sizeof(tunable_buffer),
                    "hw.pci.link.%s.%d.irq", link_name, link->l_res_index);
                if (getenv_int(tunable_buffer, &i) && PCI_INTERRUPT_VALID(i)) {
                        if (!link_valid_irq(link, i))
                                device_printf(dev,
                                    "Warning, IRQ %d is not listed as valid\n",
                                    i);
                        return (i);
                }
                snprintf(tunable_buffer, sizeof(tunable_buffer),
                    "hw.pci.link.%s.irq", link_name);
                if (getenv_int(tunable_buffer, &i) && PCI_INTERRUPT_VALID(i)) {
                        if (!link_valid_irq(link, i))
                                device_printf(dev,
                                    "Warning, IRQ %d is not listed as valid\n",
                                    i);
                        return (i);
                }
        }

        /*
         * If we have a valid BIOS IRQ, use that.  We trust what the BIOS
         * says it routed over what _CRS says the link thinks is routed.
         */
        if (PCI_INTERRUPT_VALID(link->l_bios_irq))
                return (link->l_bios_irq);

        /*
         * If we don't have a BIOS IRQ but do have a valid IRQ from _CRS,
         * then use that.
         */
        if (PCI_INTERRUPT_VALID(link->l_initial_irq))
                return (link->l_initial_irq);

        /*
         * Ok, we have no useful hints, so we have to pick from the
         * possible IRQs.  For ISA IRQs we only use interrupts that
         * have already been used by the BIOS.
         */
        best_irq = PCI_INVALID_IRQ;
        best_weight = INT_MAX;
        for (i = 0; i < link->l_num_irqs; i++) {
                pos_irq = link->l_irqs[i];
                if (pos_irq < NUM_ISA_INTERRUPTS &&
                    (pci_link_bios_isa_irqs & 1 << pos_irq) == 0)
                        continue;
                pos_weight = pci_link_interrupt_weights[pos_irq];
                if (pos_weight < best_weight) {
                        best_weight = pos_weight;
                        best_irq = pos_irq;
                }
        }

        /*
         * If this is an ISA IRQ, try using the SCI if it is also an ISA
         * interrupt as a fallback.
         */
        if (link->l_isa_irq) {
                pos_irq = AcpiGbl_FADT.SciInterrupt;
                pos_weight = pci_link_interrupt_weights[pos_irq];
                if (pos_weight < best_weight) {
                        best_weight = pos_weight;
                        best_irq = pos_irq;
                }
        }

        if (PCI_INTERRUPT_VALID(best_irq)) {
                if (bootverbose)
                        device_printf(dev, "Picked IRQ %u with weight %d\n",
                            best_irq, best_weight);
        } else
                device_printf(dev, "Unable to choose an IRQ\n");
        return (best_irq);
}

int
acpi_pci_link_route_interrupt(device_t dev, int index)
{
        struct link *link;

        if (acpi_disabled("pci_link"))
                return (PCI_INVALID_IRQ);

        ACPI_SERIAL_BEGIN(pci_link);
        link = acpi_pci_link_lookup(dev, index);
        if (link == NULL)
                panic("%s: apparently invalid index %d", __func__, index);

        /*
         * If this link device is already routed to an interrupt, just return
         * the interrupt it is routed to.
         */
        if (link->l_routed) {
                KASSERT(PCI_INTERRUPT_VALID(link->l_irq),
                    ("%s: link is routed but has an invalid IRQ", __func__));
                ACPI_SERIAL_END(pci_link);
                return (link->l_irq);
        }

        /* Choose an IRQ if we need one. */
        if (!PCI_INTERRUPT_VALID(link->l_irq)) {
                link->l_irq = acpi_pci_link_choose_irq(dev, link);

                /*
                 * Try to route the interrupt we picked.  If it fails, then
                 * assume the interrupt is not routed.
                 */
                if (PCI_INTERRUPT_VALID(link->l_irq)) {
                        acpi_pci_link_route_irqs(dev);
                        if (!link->l_routed)
                                link->l_irq = PCI_INVALID_IRQ;
                }
        }
        ACPI_SERIAL_END(pci_link);

        return (link->l_irq);
}

/*
 * This is gross, but we abuse the identify routine to perform one-time
 * SYSINIT() style initialization for the driver.
 */
static void
acpi_pci_link_identify(driver_t *driver, device_t parent)
{

        /*
         * If the SCI is an ISA IRQ, add it to the bitmask of known good
         * ISA IRQs.
         *
         * XXX: If we are using the APIC, the SCI might have been
         * rerouted to an APIC pin in which case this is invalid.  However,
         * if we are using the APIC, we also shouldn't be having any PCI
         * interrupts routed via ISA IRQs, so this is probably ok.
         */
        if (AcpiGbl_FADT.SciInterrupt < NUM_ISA_INTERRUPTS)
                pci_link_bios_isa_irqs |= (1 << AcpiGbl_FADT.SciInterrupt);
}

static device_method_t acpi_pci_link_methods[] = {
        /* Device interface */
        DEVMETHOD(device_identify,      acpi_pci_link_identify),
        DEVMETHOD(device_probe,         acpi_pci_link_probe),
        DEVMETHOD(device_attach,        acpi_pci_link_attach),
        DEVMETHOD(device_resume,        acpi_pci_link_resume),

        DEVMETHOD_END
};

static driver_t acpi_pci_link_driver = {
        "pci_link",
        acpi_pci_link_methods,
        sizeof(struct acpi_pci_link_softc),
};

DRIVER_MODULE(acpi_pci_link, acpi, acpi_pci_link_driver, 0, 0);
MODULE_DEPEND(acpi_pci_link, acpi, 1, 1, 1);