HP N54L Microserver - energy efficiency and power management

I recently worked on activating power management functions, reduce energy consumption and noise of my little HP N54L "toy". During this process I tried to avoid the usage of /etc/rc.local and set things by udev, hdparm and friends. Below are my results.

Actual results

With the following steps my system (N54L + 3xWD20EFRX HDD +1xWD5003AZEX HDD + LCD-mod + case fan mod + Debian Wheezy) uses 27W in idle mode. The USB W-LAN card uses another 10W. In active mode, e.g. compiling source code, the system runs (and boots) with around 57W. The highest power consumption observed is during startup phase with 88W.

First things first

For the following steps it might be necessary to have some packages installed, that maybe do not occur in this post. If I missed something, I appreciate a hint. Further the following steps might produce even better results with a custom kernel. I'm using the stock linux-image-3.2.0-4-amd64 kernel image as the time of writing and I have these packages installed: amd64-microcode, firmware-linux, firmware-linux-free, firmware-linux-nonfree and firmware-atheros (the latter for my WLAN card).

ASPM and ACPI

First I enabled PCIE ASPM in my (non-modded) BIOS and forced it together with ACPI via grub by changing GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub so it looks like this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force pcie_aspm=force nmi_watchdog=0"

ASPM has now been enabled as lspci prooves:

00:04.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] RS780/RS880 PCI to PCI bridge (PCIE port 0) (prog-if 00 [Normal decode])
[..]
                LnkCap: Port #1, Speed 5GT/s, Width x1, ASPM L0s L1, Latency L0 <64ns, L1 <1us
                        ClockPM- Surprise- LLActRep+ BwNot+
                LnkCtl: ASPM L0s L1 Enabled; RCB 64 bytes Disabled- Retrain- CommClk+
                        ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
[..]
00:06.0 PCI bridge: Advanced Micro Devices, Inc. [AMD] RS780 PCI to PCI bridge (PCIE port 2) (prog-if 00 [Normal decode])
[..]
                LnkCap: Port #3, Speed 5GT/s, Width x1, ASPM L0s L1, Latency L0 <64ns, L1 <1us
                        ClockPM- Surprise- LLActRep+ BwNot+
                LnkCtl: ASPM L0s L1 Enabled; RCB 64 bytes Disabled- Retrain- CommClk+
                        ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
02:00.0 USB controller: Renesas Technology Corp. uPD720201 USB 3.0 Host Controller (rev 03) (prog-if 30 [XHCI])
[..]
                LnkCap: Port #0, Speed 5GT/s, Width x1, ASPM L0s L1, Latency L0 <4us, L1 unlimited
                        ClockPM+ Surprise- LLActRep- BwNot-
                LnkCtl: ASPM L0s L1 Enabled; RCB 64 bytes Disabled- Retrain- CommClk+
                        ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
[..]
03:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5723 Gigabit Ethernet PCIe (rev 10)
[..]
                LnkCap: Port #0, Speed 2.5GT/s, Width x1, ASPM L0s L1, Latency L0 <1us, L1 <64us
                        ClockPM+ Surprise- LLActRep- BwNot-
                LnkCtl: ASPM L0s L1 Enabled; RCB 64 bytes Disabled- Retrain- CommClk+
                        ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
[..]

Even so /sys/module/pcie_aspm/parameters/policy will still show as below:

[default] performance powersave

I'll show how to set the powersave value in /sys/module/pcie_aspm/parameters/policy in the next section.

JFTR: These are my ACPI related packages installed: acpi, acpid, acpi-support and acpi-support-base.

Enable powersaving via UDEV

The following rules file /etc/udev/rules.d/90-local-n54l.rules has been inspired by a blog post. It enables powersaving modes for all PCI, SCSI and USB devices and ASPM. Further the internal RADEON cards power profile is set to the low value. There is no monitor connected usually. The file contains these rules:

SUBSYSTEM=="module", KERNEL=="pcie_aspm", ACTION=="add", TEST=="parameters/policy", ATTR{parameters/policy}="powersave"

SUBSYSTEM=="i2c", ACTION=="add", TEST=="power/control", ATTR{power/control}="auto"
SUBSYSTEM=="pci", ACTION=="add", TEST=="power/control", ATTR{power/control}="auto"
SUBSYSTEM=="usb", ACTION=="add", TEST=="power/control", ATTR{power/control}="auto"
SUBSYSTEM=="usb", ACTION=="add", TEST=="power/autosuspend", ATTR{power/autosuspend}="2"
SUBSYSTEM=="scsi", ACTION=="add", TEST=="power/control", ATTR{power/control}="auto"
SUBSYSTEM=="spi", ACTION=="add", TEST=="power/control", ATTR{power/control}="auto"

SUBSYSTEM=="drm", KERNEL=="card*", ACTION=="add", DRIVERS=="radeon", TEST=="power/control", TEST=="device/power_method", ATTR{device/power_method}="profile", ATTR{device/power_profile}="low"

SUBSYSTEM=="scsi_host", KERNEL=="host*", ACTION=="add", TEST=="link_power_management_policy", ATTR{link_power_management_policy}="min_power"

Set harddrives spindown timeout

I decided to sent my system drive to standby after 20 minutes and the RAID drives after 15 minutes. This is usually ok, because the RAID isn't always used. hdparm is the right tool to realize this. Many people use the /dev/disk/by-uuid/... syntax here, to avoid having to touch the configuration file if some system configuration changes. Because I'm running a RAID, I couldn't use this syntax, although it might be possible to use /dev/disk/by-id/... instead. Well for the moment I stay with the configuration below. The relevant part of /etc/hdparm.conf is:

[..]

# system harddrive
/dev/sda {
        spindown_time = 240
}

# below are the WD20EFRX drives
/dev/sdb {
        spindown_time = 180
}

/dev/sdc {
        spindown_time = 180
}

/dev/sdd {
        spindown_time = 180
}

Idle mode

When there is nothing to do for the system, all I hear is the (still a bit noisy) fan of the power supply, which I might replace in the future too. Either by testing a different fan or by replacing the whole power supply unit by the fanless FORTRON FSP150-50TNF or (even better) a picoPSU.

The system currently shows a power consumption of around 37W in idle mode whereas the USB W-LAN card itself needs around 10W. There is a possibility to enable power savings mode for this card too. I could add this entry to /etc/udev/rules.d/90-local-n54l.rules:

SUBSYSTEM=="net", ACTION=="add", KERNEL=="wlan*" RUN+="/usr/bin/iw dev %k set power_save on"

But it turned out that the connection became a bit unstable after it. So I don't use this rule.

More on the road

There are a lot more options one can easily find via $search_engine. The N54L system could be brought to sleep and woken up by LAN via Wake-on-LAN (WOL). This is a feature I don't use. I've also read rumors about enabling different sleep/suspend states of the system, which seems to require to install a modded BIOS. Well, I'll post news and changes if they happen to come;)

Getting the TP-Link TL-WN772N(C) USB WLAN stick to work

After installing Debian wheezy on the N54L microserver I wanted to setup a stable WLAN connection. The stick should have out-of-the-box kernel support. First I bought a cheap ISY IWL 2000 N150 WLAN USB micro adapter (probably a branded Belkin F7D1102). I contains a Realtek chipset and although it did seem to work on my laptop with Sid running, I did not get it to work on the server. I refused to download and compile third-party software.

So I searched this site. I got the impression, that the "only" recent chipsets with reasonable support in the Linux kernel are Atheros chipsets(?). Checking the local suppliers I decided to buy a TP-Link TL-WN722NC USB stick. I've downloaded the firmware-atheros package and loaded the ath9k_htc module and voilà, the stick is running:

ath9k_htc              48534  0 
ath9k_common           12728  1 ath9k_htc
ath9k_hw              322112  2 ath9k_common,ath9k_htc
ath                    21370  3 ath9k_hw,ath9k_common,ath9k_htc
mac80211              192806  1 ath9k_htc
cfg80211              137243  3 ath,mac80211,ath9k_htc
usbcore               128741  5 ehci_hcd,ohci_hcd,usbhid,ath9k_htc

[..]
Bus 001 Device 003: ID 0cf3:9271 Atheros Communications, Inc. AR9271 802.11n
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass          255 Vendor Specific Class
  bDeviceSubClass       255 Vendor Specific Subclass
  bDeviceProtocol       255 Vendor Specific Protocol
  bMaxPacketSize0        64
  idVendor           0x0cf3 Atheros Communications, Inc.
  idProduct          0x9271 AR9271 802.11n
  bcdDevice            1.08
  iManufacturer          16 ATHEROS
  iProduct               32 USB2.0 WLAN
  iSerial                48 12345
  bNumConfigurations      1
[..]

To setup the connection I decided to install the network-manager package and write the configuration file myself:

[connection]
id=<myID>
uuid=<myUUID>
type=802-11-wireless
autoconnect=true

[802-11-wireless]
ssid=<mySSID>
mode=infrastructure
mac-address=<myMACADDR>
seen-bssids=<myBSSIDS>
security=802-11-wireless-security

[802-11-wireless-security]
key-mgmt=wpa-psk
psk=<myPASSPHR>

[ipv4]
method=auto

[ipv6]
method=auto

[..]
wlan1     IEEE 802.11bgn  ESSID:"<ESSID>"
          Mode:Managed  Frequency:2.467 GHz  Access Point: <MACADDR>
          Bit Rate=54 Mb/s   Tx-Power=20 dBm
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality=49/70  Signal level=-61 dBm
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:61   Missed beacon:0
[..]

The connection comes up and it seems pretty stable. After two weeks of operation there were still no connection losses or time outs. After lease time has been reached, the IP address gets renewed. And that's it! The stick runs perfectly fine for me and I'm happy with it.

Abit AirPace, ath5k and eduroam

I tried to connect my university workstation to the wireless eduroam network on the campus. The workstation was delivered with an Abit AirPace wlan card (probably an Atheros 5006 chipset). The first thing necessary was the ath5k kernel module (my first shot using ndiswrapper didn't work). Both Debian lenny and Ubuntu intrepid-updates provide it.

Now there are generally 3 ways to connect to the AP. All making use of wpasupplicant. Further the certificate (may differ for the universities) is necessary.

/etc/wpa_supplicant/wpa_supplicant.conf

This is described at the sites of my university. It's written in German, but it should still be easy to understand. Let's just mention the snippet for /etc/wpa_supplicant/wpa_supplicant.conf:

ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=0
eapol_version=2
ap_scan=1
fast_reauth=1

network={
        ssid="eduroam"
        key_mgmt=WPA-EAP
        proto=RSN
        pairwise=CCMP
        group=TKIP
        eap=TTLS
        anonymous_identity="anonymous@tu-dresden.de"
        identity="****@tu-dresden.de"
        password="****"
        ca_cert="/etc/wpa_supplicant/TUD-CACert.pem"
        phase2="auth=PAP"

}

Instead of the script suggested at the site above, you can also use this snippet in /etc/network/interfaces:

auto wlan0
iface wlan0 inet dhcp
        wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

/etc/network/interfaces

It is also possible to put the values directly into /etc/network/interfaces:

auto wlan0
iface wlan0 inet dhcp
        wpa-ssid eduroam
        wpa-proto RSN
        wpa-group CCMP TKIP
        wpa-pairwise CCMP TKIP
        wpa-key-mgmt WPA-EAP
        wpa-eap TTLS
        wpa-ca-cert /etc/wpa_supplicant/TUD-CACert.pem
        wpa-phase2 "auth=PAP"
        wpa-anonymous-identity anonymous@tu-dresden.de
        wpa-identity ****@tu-dresden.de
        wpa-password ****

network-manager

Here is a screenshot of the authentication dialog:

So now everybody at the University of Dresden wanting to use eduroam should hopefully be able to configure this connection on his Debian or Ubuntu system.