Line data    Source code

       1             : // SPDX-License-Identifier: GPL-2.0
       2             : /*
       3             :  * Support routines for initializing a PCI subsystem
       4             :  *
       5             :  * Extruded from code written by
       6             :  *      Dave Rusling (david.rusling@reo.mts.dec.com)
       7             :  *      David Mosberger (davidm@cs.arizona.edu)
       8             :  *      David Miller (davem@redhat.com)
       9             :  */
      10             : 
      11             : #include <linux/kernel.h>
      12             : #include <linux/pci.h>
      13             : #include <linux/errno.h>
      14             : #include <linux/ioport.h>
      15             : #include <linux/cache.h>
      16             : #include "pci.h"
      17             : 
      18           0 : void pci_assign_irq(struct pci_dev *dev)
      19             : {
      20             :         u8 pin;
      21           0 :         u8 slot = -1;
      22           0 :         int irq = 0;
      23           0 :         struct pci_host_bridge *hbrg = pci_find_host_bridge(dev->bus);
      24             : 
      25           0 :         if (!(hbrg->map_irq)) {
      26             :                 pci_dbg(dev, "runtime IRQ mapping not provided by arch\n");
      27           0 :                 return;
      28             :         }
      29             : 
      30             :         /*
      31             :          * If this device is not on the primary bus, we need to figure out
      32             :          * which interrupt pin it will come in on. We know which slot it
      33             :          * will come in on because that slot is where the bridge is. Each
      34             :          * time the interrupt line passes through a PCI-PCI bridge we must
      35             :          * apply the swizzle function.
      36             :          */
      37           0 :         pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &pin);
      38             :         /* Cope with illegal. */
      39           0 :         if (pin > 4)
      40           0 :                 pin = 1;
      41             : 
      42           0 :         if (pin) {
      43             :                 /* Follow the chain of bridges, swizzling as we go. */
      44           0 :                 if (hbrg->swizzle_irq)
      45           0 :                         slot = (*(hbrg->swizzle_irq))(dev, &pin);
      46             : 
      47             :                 /*
      48             :                  * If a swizzling function is not used, map_irq() must
      49             :                  * ignore slot.
      50             :                  */
      51           0 :                 irq = (*(hbrg->map_irq))(dev, slot, pin);
      52           0 :                 if (irq == -1)
      53           0 :                         irq = 0;
      54             :         }
      55           0 :         dev->irq = irq;
      56             : 
      57             :         pci_dbg(dev, "assign IRQ: got %d\n", dev->irq);
      58             : 
      59             :         /*
      60             :          * Always tell the device, so the driver knows what is the real IRQ
      61             :          * to use; the device does not use it.
      62             :          */
      63           0 :         pci_write_config_byte(dev, PCI_INTERRUPT_LINE, irq);
      64             : }