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Dell_Latitude_XT


Contents

General

This tablet is equipped with ultra low voltage Intel Core2 processor, chipset is based on ATI RS600 (with ATI Xpress 1250 integrated graphics), 12.1" display with N-Trig's digitizer, Broadcom wired and wireless ethernet.

BIOS

This howto was written based on experience with A02 and A03 revision of BIOS. A02 revision worked just fine, A03 with kernel commandline parameter acpi_osi=Linux sometimes panics during kernel initialization. It is possible that fix mentioned in section "Hardware support" also fixes this issue.

Installation

Gentoo 2008.0 LiveCD boots without problems. System is usually shipped with disk containing one big NTFS partition, which has to be shrinked using ntfsresize and then resized using fdisk or similar tool.

Hardware support

Warning: Text in this section changes a lot, so take it only as "currently known state" of this issue. This warning disappears when the final solution will be available.

Update: It is possible that this laptop doesn't do "clean reboot", so if something goes wrong and you reboot it, that 'bad' thing can survive and somehow affect your system, or at least it may behave differently as if it was turned off and on again:). After cold reboot, kernel paramter hpet=disable' seems to help as well, even with CONFIG_CPU_IDLE enabled.

Update: The text below is not valid anymore, it turned out to be problem with CPU_IDLE; after disabling CONFIG_CPU_IDLE in kernel configuration the system seems to run fine even if it enters C2 or C3.

First of all, warning: although installation works without apparent problems, there is power management issue (at least with 2.6.25-r7 and 2.6.26 kernels), which manifests e.g. as random stopping of movie playback in mplayer, high (sometimes over 10000) number of wakeups in powertop and generally, with random program freezes for few seconds. You can work around this problem by adding processor.max_cstate=1 to kernel parameters. This fix prevents CPU entering lower power-saving states, so you end up with higher power consumption and lower battery time.

More information below.

Laptop hardware

ACPI buttons

Seem to work, but unfortunately, sleep button doesn't seem to produce any events.

Backlight, wifi and bluetooth control

In order to get these things working properly, you need to:

Code: smbios installation
emerge libsmbios

Also, having hal compiled with dell USE-flag exposes these informations further to the system.

Bluetooth

Depends on bluetooth module selection, in this case Dell Bluetooth module 350 is standard USB Bluetooth adapter supported by linux.

Fingerprint scanner

USB device "SGS Thomson Microelectronics Fingerprint Reader", supported by thinkfinger. The only step needed is:

Code: ThinkFinger installation
emerge thinkfinger

Firewire

Not tested, but driver ohci1394 seems to load correctly.

Graphics card

ATI closed-source drivers from ati-drivers ebuild seem to work just fine, after patching them to compile with 2.6.26 kernel. Another viable option is open-source radeon driver, but unfortunately, it doesn't yet support 3D acceleration on RS600 chipset.

SD Card reader

Standard device supported by sdhci driver. When using 2.6.26 kernel, it has however problems with detecting card insertion, so it works correctly first time after reboot, when card is inside and the sdhci driver is removed and installed again. Subsequent attempts did not work. With CPU_IDLE disabled it seems to run fine.

Sound

Supported by kernel, driver is snd-hda-intel.

Suspend/resume

Both suspend to RAM and to disk seem to work out of the box. :)

Touchpad and trackpoint

So far it is more convenient to use the default mouse driver, although the device is ALPS touchpad (using supported by synaptics driver). When using the synaptics driver, the device doesn't behave properly, e.g. mouse buttons don't click as neccessary. If you are brave enough, in order to use this protocol, you need to modify your xorg.conf (you can disable SHMConfig if you don't plan to use synclient utility):

Code: xorg.conf
Section "InputDevice"
       Driver      "synaptics"
       Identifier  "Mouse0"
       Option      "Protocol" "alps"
       Option      "Device" "/dev/input/mice"
       Option      "SHMConfig" "on"
EndSection

If someone finds out proper configuration for this device and synaptics driver, please update this page.

Touchscreen

This device has currently no support, but it looks like standard HID device and its description in lsusb -v is quite verbose, so it should be possible to write a driver. To get it working as a (maybe limited) HID device, please read [1].

Wired Ethernet

Works without any apparent problems using tg3 kernel driver.

Wireless Ethernet

Depending on selected components, wireless adapter can be one of Dell's wireless adapters, which are usually based on Broadcom chipset. Some of the cards are supported by b43 kernel driver, but at least for Dell Wireless adapter 1390 you for now need to use ndiswrapper and windows NDIS driver.

Docking station

Most devices use USB (even DVD-RW), and work out-of-box; replicated ethernet port worked as well.

DVD/RW

Attached to USB, recognized by usb-storage module, reads media correctly (except that SCSI layer seemed to offline it once upon a time, but that might be issue connected with CPU_IDLE problems mentioned above), burning works as well.

Serial port

Serial port is currently not supported, it reports itself as TUB3410 device, which seems like device supported by ti_usb_3410_5052, even after forcing vendor and product id, the driver doesn't claim it.

VGA/DVI output

Not tested.

Power management

Looks like laptop with LED backlight should be capable of living on 6cell battery for something around 2:45, maybe even 3:00. Minimal vs. maximal backlight intensity made 2W difference (but just quickly measured, the value can be different), wireless features (bluetooth and wifi) enabled (but otherwise inactive) are worth ~0.6W (again just quick measurement).

Minimal power consumption

Measured with PowerTOP, minimal power consumption I was able to get, was 11.5W, which should be (again with 6cell battery and LED backlight) more than 3:30, but some drastic measurements were neccessary (together with disabling any wireless components):

Code: Power management settings
hdparm -B 1 /dev/sda # enable aggressive hard driver power management
echo "7" >/sys/class/thermal/cooling_device0/cur_state
echo "7" >/sys/class/thermal/cooling_device1/cur_state # Both 0 and 1 seem to control display backlight
echo "10" >/sys/class/thermal/cooling_device2/cur_state
echo "10" >/sys/class/thermal/cooling_device3/cur_state # No idea what these two actually do
rmmod ndiswrapper
/etc/init.d/xdm stop # we are going to run bare console with no X server

Devices/drivers consuming a lot of power/CPU time

Booting on battery

It looks like BIOS itself is able to to lots of things to save power. It apparently underclocks either CPU or even system bus, as when started off-battery, linux runs visibly slower; also repainting of screen is quite visible. Processor can not be cloced higher than 800MHz (not sure whether this is cpufreq/cpufreq_ondemand issue, or BIOS one), and system as whole reacts really slowly. After reboot the systems seems to be even slower.

See also

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Last modified: Fri, 15 Aug 2008 12:47:00 +0000 Hits: 1,053