ACPI: Add "acpi.power_nocheck=1" to disable power state check in power transition

   Maybe the incorrect power state is returned on the bogus bios, which
is different with the real power state. For example: the bios returns D0
state and the real power state is D3. OS expects to set the device to D0
state. In  such case if OS uses the power state returned by the BIOS and
checks the device power state very strictly in power transition, the device
can't be transited to the correct power state.

   So the boot option of "acpi.power_nocheck=1" is added to avoid checking
the device power in the course of device power transition.

http://bugzilla.kernel.org/show_bug.cgi?id=8049
http://bugzilla.kernel.org/show_bug.cgi?id=11000

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Li Shaohua <shaohua.li@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 44d1bd142edf..99cf83fd6947 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -251,6 +251,14 @@ and is between 256 and 4096 characters. It is defined in the file
                         Warning: Many of these options can produce a lot of
                         output and make your system unusable. Be very careful.
 
+        acpi.power_nocheck=     [HW,ACPI]
+                        Format: 1/0 enable/disable the check of power state.
+                        On some bogus BIOS the _PSC object/_STA object of
+                        power resource can't return the correct device power
+                        state. In such case it is unneccessary to check its
+                        power state again in power transition.
+                        1 : disable the power state check
+
         acpi_pm_good    [X86-32,X86-64]
                         Override the pmtimer bug detection: force the kernel
                         to assume that this machine's pmtimer latches its value