LXR linux/drivers/acpi/reboot.c

   1// SPDX-License-Identifier: GPL-2.0
   2
   3#define pr_fmt(fmt) "ACPI: " fmt
   4
   5#include <linux/pci.h>
   6#include <linux/acpi.h>
   7#include <acpi/reboot.h>
   8#include <linux/delay.h>
   9
  10#ifdef CONFIG_PCI
  11static void acpi_pci_reboot(struct acpi_generic_address *rr, u8 reset_value)
  12{
  13        unsigned int devfn;
  14        struct pci_bus *bus0;
  15
  16        /* The reset register can only live on bus 0. */
  17        bus0 = pci_find_bus(0, 0);
  18        if (!bus0)
  19                return;
  20        /* Form PCI device/function pair. */
  21        devfn = PCI_DEVFN((rr->address >> 32) & 0xffff,
  22                          (rr->address >> 16) & 0xffff);
  23        pr_debug("Resetting with ACPI PCI RESET_REG.\n");
  24        /* Write the value that resets us. */
  25        pci_bus_write_config_byte(bus0, devfn,
  26                        (rr->address & 0xffff), reset_value);
  27}
  28#else
  29static inline void acpi_pci_reboot(struct acpi_generic_address *rr,
  30                                   u8 reset_value)
  31{
  32        pr_warn_once("PCI configuration space access is not supported\n");
  33}
  34#endif
  35
  36void acpi_reboot(void)
  37{
  38        struct acpi_generic_address *rr;
  39        u8 reset_value;
  40
  41        if (acpi_disabled)
  42                return;
  43
  44        rr = &acpi_gbl_FADT.reset_register;
  45
  46        /* ACPI reset register was only introduced with v2 of the FADT */
  47
  48        if (acpi_gbl_FADT.header.revision < 2)
  49                return;
  50
  51        /* Is the reset register supported? The spec says we should be
  52         * checking the bit width and bit offset, but Windows ignores
  53         * these fields */
  54        if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER))
  55                return;
  56
  57        reset_value = acpi_gbl_FADT.reset_value;
  58
  59        /* The reset register can only exist in I/O, Memory or PCI config space
  60         * on a device on bus 0. */
  61        switch (rr->space_id) {
  62        case ACPI_ADR_SPACE_PCI_CONFIG:
  63                acpi_pci_reboot(rr, reset_value);
  64                break;
  65
  66        case ACPI_ADR_SPACE_SYSTEM_MEMORY:
  67        case ACPI_ADR_SPACE_SYSTEM_IO:
  68                pr_debug("ACPI MEMORY or I/O RESET_REG.\n");
  69                acpi_reset();
  70                break;
  71        }
  72
  73        /*
  74         * Some platforms do not shut down immediately after writing to the
  75         * ACPI reset register, and this results in racing with the
  76         * subsequent reboot mechanism.
  77         *
  78         * The 15ms delay has been found to be long enough for the system
  79         * to reboot on the affected platforms.
  80         */
  81        mdelay(15);
  82}
  83