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 } 70