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 |
11 | static 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(domain: 0, busnr: 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(bus: bus0, devfn, |
26 | where: (rr->address & 0xffff), val: reset_value); |
27 | } |
28 | #else |
29 | static 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 | |
36 | void 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 | |