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