blob: 755baf2ca70ad5b44676390242038a737e0f46a2 [file] [log] [blame]
Aaron Durbin4d387042008-07-16 23:27:08 +02001
2#include <linux/pci.h>
3#include <linux/acpi.h>
4#include <acpi/reboot.h>
5
6void acpi_reboot(void)
7{
8 struct acpi_generic_address *rr;
9 struct pci_bus *bus0;
10 u8 reset_value;
11 unsigned int devfn;
12
13 if (acpi_disabled)
14 return;
15
16 rr = &acpi_gbl_FADT.reset_register;
17
Zhao Yakui8fd14592008-10-17 14:22:27 -040018 /*
19 * Is the ACPI reset register supported?
20 *
21 * According to ACPI 3.0, FADT.flags.RESET_REG_SUP indicates
22 * whether the ACPI reset mechanism is supported.
23 *
24 * However, some boxes have this bit clear, yet a valid
25 * ACPI_RESET_REG & RESET_VALUE, and ACPI reboot is the only
26 * mechanism that works for them after S3.
27 *
28 * This suggests that other operating systems may not be checking
29 * the RESET_REG_SUP bit, and are using other means to decide
30 * whether to use the ACPI reboot mechanism or not.
31 *
32 * So when acpi reboot is requested,
33 * only the reset_register is checked. If the following
34 * conditions are met, it indicates that the reset register is supported.
35 * a. reset_register is not zero
36 * b. the access width is eight
37 * c. the bit_offset is zero
38 */
39 if (!(rr->address) || rr->bit_width != 8 || rr->bit_offset != 0)
Aaron Durbin4d387042008-07-16 23:27:08 +020040 return;
41
42 reset_value = acpi_gbl_FADT.reset_value;
43
44 /* The reset register can only exist in I/O, Memory or PCI config space
45 * on a device on bus 0. */
46 switch (rr->space_id) {
47 case ACPI_ADR_SPACE_PCI_CONFIG:
48 /* The reset register can only live on bus 0. */
49 bus0 = pci_find_bus(0, 0);
50 if (!bus0)
51 return;
52 /* Form PCI device/function pair. */
53 devfn = PCI_DEVFN((rr->address >> 32) & 0xffff,
54 (rr->address >> 16) & 0xffff);
55 printk(KERN_DEBUG "Resetting with ACPI PCI RESET_REG.");
56 /* Write the value that resets us. */
57 pci_bus_write_config_byte(bus0, devfn,
58 (rr->address & 0xffff), reset_value);
59 break;
60
61 case ACPI_ADR_SPACE_SYSTEM_MEMORY:
62 case ACPI_ADR_SPACE_SYSTEM_IO:
63 printk(KERN_DEBUG "ACPI MEMORY or I/O RESET_REG.\n");
64 acpi_hw_low_level_write(8, reset_value, rr);
65 break;
66 }
67 /* Wait ten seconds */
68 acpi_os_stall(10000000);
69}