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 #ifdef CONFIG_PCI
   8 static void acpi_pci_reboot(struct acpi_generic_address *rr, u8 reset_value)
   9 {
  10         unsigned int devfn;
  11         struct pci_bus *bus0;
  12
  13         /* The reset register can only live on bus 0. */
  14         bus0 = pci_find_bus(0, 0);
  15         if (!bus0)
  16                 return;
  17         /* Form PCI device/function pair. */
  18         devfn = PCI_DEVFN((rr->address >> 32) & 0xffff,
  19                           (rr->address >> 16) & 0xffff);
  20         pr_debug("Resetting with ACPI PCI RESET_REG.\n");
  21         /* Write the value that resets us. */
  22         pci_bus_write_config_byte(bus0, devfn,
  23                         (rr->address & 0xffff), reset_value);
  24 }
  25 #else
  26 static inline void acpi_pci_reboot(struct acpi_generic_address *rr,
  27                                    u8 reset_value)
  28 {
  29         pr_warn_once("PCI configuration space access is not supported\n");
  30 }
  31 #endif
  32
  33 void acpi_reboot(void)
  34 {
  35         struct acpi_generic_address *rr;
  36         u8 reset_value;
  37
  38         if (acpi_disabled)
  39                 return;
  40
  41         rr = &acpi_gbl_FADT.reset_register;
  42
  43         /* ACPI reset register was only introduced with v2 of the FADT */
  44
  45         if (acpi_gbl_FADT.header.revision < 2)
  46                 return;
  47
  48         /* Is the reset register supported? The spec says we should be
  49          * checking the bit width and bit offset, but Windows ignores
  50          * these fields */
  51         if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER))
  52                 return;
  53
  54         reset_value = acpi_gbl_FADT.reset_value;
  55
  56         /* The reset register can only exist in I/O, Memory or PCI config space
  57          * on a device on bus 0. */
  58         switch (rr->space_id) {
  59         case ACPI_ADR_SPACE_PCI_CONFIG:
  60                 acpi_pci_reboot(rr, reset_value);
  61                 break;
  62
  63         case ACPI_ADR_SPACE_SYSTEM_MEMORY:
  64         case ACPI_ADR_SPACE_SYSTEM_IO:
  65                 printk(KERN_DEBUG "ACPI MEMORY or I/O RESET_REG.\n");
  66                 acpi_reset();
  67                 break;
  68         }
  69 }