tree f15195d5e4f55eafe6b956b2f7b28ee9ab4df1da
parent 8777c793d6a24c7f3adf52b1b1086e9706de4589
author Alex Chiang <achiang@canonical.com> 1271772194 -0600
committer Len Brown <len.brown@intel.com> 1273082692 -0400

ACPI: DMI init_set_sci_en_on_resume for multiple Lenovo ThinkPads

Multiple Lenovo ThinkPad models with Intel Core i5/i7 CPUs can
successfully suspend/resume once, and then hang on the second s/r
cycle.

We got confirmation that this was due to a BIOS defect. The BIOS
did not properly set SCI_EN coming out of S3. The BIOS guys
hinted that The Other Leading OS ignores the fact that hardware
owns the bit and sets it manually.

In any case, an existing DMI table exists for machines where this
defect is a known problem. Lenovo promise to fix their BIOS, but
for folks who either won't or can't upgrade their BIOS, allow
Linux to workaround the issue.

https://bugzilla.kernel.org/show_bug.cgi?id=15407
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/532374

Confirmed by numerous testers in the launchpad bug that using
acpi_sleep=sci_force_enable fixes the issue. We add the machines
to acpisleep_dmi_table[] to automatically enable this workaround.

Cc: stable@kernel.org
Cc: Colin King <colin.king@canonical.com>
Signed-off-by: Alex Chiang <achiang@canonical.com>
Signed-off-by: Len Brown <len.brown@intel.com>