Installing Debian on Thinkpad T420s |

Installing Debian on Thinkpad T420s


I've passed the following Linux parameters via GRUB's /etc/default/grub:

GRUB_CMDLINE_LINUX_DEFAULT="quiet pcie_aspm=force i915.semaphores=1 i915.i915_enable_rc6=1 i915.i915_enable_fbc=1 i915.lvds_downclock=1"

i915.semaphores=1: "Enablement of semaphores solves several stability issues on Ivy Bridge graphics cards, such as GPU hangs, and improved stability and performance on Sandy Bridge generation of graphics cards". See Intel 2011Q4 graphics package for more details.


I've experienced instable wireless, often it would just seize to function. The bug is described here on Intel Linux Wireless

To remedy the problem, I did the following:

# echo "options iwlwifi 11n_disable=1" > /etc/modprobe.d/iwlwifi.conf
# update-initramfs -u

Since I don't like rebooting when I really don't have to, I did the following to activate the changes:

# modprobe -r iwlwifi
# modprobe iwlwifi

Detailed information about the wireless card:

03:00.0 Network controller: Intel Corporation Centrino Advanced-N 6205 (rev 34)
Subsystem: Intel Corporation Centrino Advanced-N 6205 AGN
Flags: bus master, fast devsel, latency 0, IRQ 48
Memory at f2900000 (64-bit, non-prefetchable) [size=8K]
Kernel driver in use: iwlwifi

Battery life

I've added the following to/etc/rc.local to enhance the battery life. With these in place, powertop lists all the "Toggleables" as "Good":

# Dynamic power save
iw wlan0 set power_save on

echo 0 > /proc/sys/kernel/nmi_watchdog

# Enable SATA link power management for /dev/sda
echo min_power > /sys/class/scsi_host/host0/link_power_management_policy
echo min_power > /sys/class/scsi_host/host1/link_power_management_policy

# VM writeback timeout
echo 1500 > /proc/sys/vm/dirty_writeback_centisecs

# Sound power management
echo Y > /sys/module/snd_hda_intel/parameters/power_save_controller
echo 1 > /sys/module/snd_hda_intel/parameters/power_save

# Power aware CPU scheduler
echo 1 > /sys/devices/system/cpu/sched_mc_power_savings

gmail torstein.k.johansen @ gmail ~ twitter @torsteinkrause ~