drivers/acpi/reboot.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/pci.h>
   4 #include <linux/acpi.h>
   5 #include <acpi/reboot.h>
   6
   7 void acpi_reboot(void)
   8 {
   9         struct acpi_generic_address *rr;
  10         struct pci_bus *bus0;
  11         unsigned int devfn;
  12         u8 reset_value;
  13
  14         if (acpi_disabled)
  15                 return;
  16
  17         rr = &acpi_gbl_FADT.reset_register;
  18
  19         /* ACPI reset register was only introduced with v2 of the FADT */
  20
  21         if (acpi_gbl_FADT.header.revision < 2)
  22                 return;
  23
  24         /* Is the reset register supported? The spec says we should be
  25          * checking the bit width and bit offset, but Windows ignores
  26          * these fields */
  27         if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER))
  28                 return;
  29
  30         reset_value = acpi_gbl_FADT.reset_value;
  31
  32         /* The reset register can only exist in I/O, Memory or PCI config space
  33          * on a device on bus 0. */
  34         switch (rr->space_id) {
  35         case ACPI_ADR_SPACE_PCI_CONFIG:
  36                 /* The reset register can only live on bus 0. */
  37                 bus0 = pci_find_bus(0, 0);
  38                 if (!bus0)
  39                         return;
  40                 /* Form PCI device/function pair. */
  41                 devfn = PCI_DEVFN((rr->address >> 32) & 0xffff,
  42                                   (rr->address >> 16) & 0xffff);
  43                 printk(KERN_DEBUG "Resetting with ACPI PCI RESET_REG.\n");
  44                 /* Write the value that resets us. */
  45                 pci_bus_write_config_byte(bus0, devfn,
  46                                 (rr->address & 0xffff), reset_value);
  47                 break;
  48
  49         case ACPI_ADR_SPACE_SYSTEM_MEMORY:
  50         case ACPI_ADR_SPACE_SYSTEM_IO:
  51                 printk(KERN_DEBUG "ACPI MEMORY or I/O RESET_REG.\n");
  52                 acpi_reset();
  53                 break;
  54         }
  55 }