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authorZhao Yakui <yakui.zhao@intel.com>2008-10-17 14:22:27 -0400
committerLen Brown <len.brown@intel.com>2008-10-18 01:01:12 -0400
commit8fd145917fb62368a9b80db59562c20576238f5a (patch)
tree42b81ee305b6f35e98aed2690f696b32cb5c864b /drivers/acpi/reboot.c
parent3fa8749e584b55f1180411ab1b51117190bac1e5 (diff)
downloadlinux-8fd145917fb62368a9b80db59562c20576238f5a.tar.bz2
ACPI: Ingore the RESET_REG_SUP bit when using ACPI reset mechanism
According to ACPI 3.0, FADT.flags.RESET_REG_SUP indicates whether the ACPI reboot mechanism is supported. However, some boxes have this bit clear, have a valid ACPI_RESET_REG & RESET_VALUE, and ACPI reboot is the only mechanism that works for them after S3. This suggests that other operating systems may not be checking the RESET_REG_SUP bit, and are using other means to decide whether to use the ACPI reboot mechanism or not. Here we stop checking RESET_REG_SUP. Instead, When acpi reboot is requested, only the reset_register is checked. If the following conditions are met, it indicates that the reset register is supported. a. reset_register is not zero b. the access width is eight c. the bit_offset is zero http://bugzilla.kernel.org/show_bug.cgi?id=7299 http://bugzilla.kernel.org/show_bug.cgi?id=1148 Signed-off-by: Zhao Yakui <yakui.zhao@intel.com> Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'drivers/acpi/reboot.c')
-rw-r--r--drivers/acpi/reboot.c25
1 files changed, 22 insertions, 3 deletions
diff --git a/drivers/acpi/reboot.c b/drivers/acpi/reboot.c
index a6b662c00b67..755baf2ca70a 100644
--- a/drivers/acpi/reboot.c
+++ b/drivers/acpi/reboot.c
@@ -15,9 +15,28 @@ void acpi_reboot(void)
rr = &acpi_gbl_FADT.reset_register;
- /* Is the reset register supported? */
- if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER) ||
- rr->bit_width != 8 || rr->bit_offset != 0)
+ /*
+ * Is the ACPI reset register supported?
+ *
+ * According to ACPI 3.0, FADT.flags.RESET_REG_SUP indicates
+ * whether the ACPI reset mechanism is supported.
+ *
+ * However, some boxes have this bit clear, yet a valid
+ * ACPI_RESET_REG & RESET_VALUE, and ACPI reboot is the only
+ * mechanism that works for them after S3.
+ *
+ * This suggests that other operating systems may not be checking
+ * the RESET_REG_SUP bit, and are using other means to decide
+ * whether to use the ACPI reboot mechanism or not.
+ *
+ * So when acpi reboot is requested,
+ * only the reset_register is checked. If the following
+ * conditions are met, it indicates that the reset register is supported.
+ * a. reset_register is not zero
+ * b. the access width is eight
+ * c. the bit_offset is zero
+ */
+ if (!(rr->address) || rr->bit_width != 8 || rr->bit_offset != 0)
return;
reset_value = acpi_gbl_FADT.reset_value;