280 lines
9.8 KiB
Markdown
280 lines
9.8 KiB
Markdown
---
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title: Miscellaneous
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x-toc-enable: true
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...
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TODO: this page is very old, and could do with an update.
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High Pitched Whining Noise on Idle in Arch-based distros
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==============================================================
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The following removes most of the noise. It reduces what is a high
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frequency whine (that not everyone can hear) to a slight buzz (which
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most people can't hear or doesn't bother most people).
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This is not perfect! The full solution is still not discovered but this
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is a step towards that. Also, in some instances you will need to run
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'sudo powertop --auto-tune' again. This needs to be implemented
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properly in coreboot itself!
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On the X60 with coreboot or libreboot, there is a high pitched sound
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when idle. So far we have use processor.max\_cstate=2 or idle=halt in
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GRUB. These consume power. Stop using them!
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Be root
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su -
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Installed powertop:
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pacman -S powertop
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and added the following to /etc/systemd/system/powertop.service :
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```
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[Unit]
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Description=Powertop tunings
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[Service]
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Type=oneshot
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RemainAfterExit=no
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ExecStart=/usr/bin/powertop --auto-tune
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"powertop --auto-tune" still needs a terminal for some reason. Possibly a bug?
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Environment="TERM=xterm"
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[Install]
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WantedBy=multi-user.target
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```
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Finally, as root do that:
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systemctl enable powertop
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systemctl start powertop
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The next time you boot the system, the buzz will be gone.
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Might want to run with --calibrate first
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If powertop doesn't work, another way (reduces battery life slightly)
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is to add *processor.max\_cstate=2* to the *linux* line in grub.cfg,
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using [this guide](../linux/grub_cbfs.md).
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X60/T60: Serial port - how to use (for dock owners)
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[Note: using a grsec enabled kernel will disable the powertop function. ](https://en.wikibooks.org/wiki/Grsecurity/Appendix/Grsecurity_and_PaX_Configuration_Options)
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===================================================
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For the Thinkpad X60 you can use the "UltraBase X6" dock (for the
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X60 Tablet it is called X6 Tablet UltraBase). For the ThinkPad T60, you
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can use the "Advanced Mini Dock".
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If you are using one of the ROM images with 'serial' in the name, then
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you have serial port enabled in libreboot and you have memtest86+
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included inside the ROM. Connect your null modem cable to the serial
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port on the dock and connect the other end to a 2nd system using your
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USB Serial adapter.
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On the 2nd system, you can try this (using `screen`):
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sudo screen /dev/ttyUSB0 115200
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How to quit Screen: Ctrl+A then release and press K, and then press
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Y.
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There are also others like Minicom but Screen works nicely.
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By doing this before booting the X60/T60, you will see console output
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from libreboot. You will also see GRUB displaying on the serial output,
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and you will be able to see MemTest86+ on the serial output aswell. You
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can also configure your distro so that a terminal (TTY) is accessible
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from the serial console.
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The following guide is for Ubuntu, but it should work in Debian and
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Devuan, to enable a serial console using GeTTY:\
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<https://help.ubuntu.com/community/SerialConsoleHowto>
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Note: part of the tutorial above requires changing your grub.cfg. Just
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change the `linux` line to add instructions for enabling getty. See
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[../linux/grub\_cbfs.md](../linux/grub_cbfs.md).
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Finetune backlight control on intel gpu's
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=========================================
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Sometimes the backlight control value (BLC\_PWM\_CTL) set by libreboot
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is not ideal. The result is either flicker, which could cause nausea or
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epilepsy or an uneven backlight and/or coil whine coming from the
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display. To fix this a different value for the gpu reg BLC\_PWM\_CTL
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needs to be set. See p94 of
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<https://01.org/sites/default/files/documentation/g45_vol_3_register_0_0.pdf>
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for more information on this reg. The tool for setting registry values
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on intel gpu's is included in intel-gpu-tools. Install intel-gpu-tools:
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sudo apt-get install intel-gpu-tools
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You can set values:
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sudo intel_reg write 0x00061254 your_value_in_C_hex_format
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NOTE: on older versions of this utility, use `intel_reg_write` instead.
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The value set has the following structure: bits [31:16] is PWM
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divider. PWM / PWM\_divider = frequency bits [15:0] is the duty cycle
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and determines the portion of the backlight modulation frequency. A
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value of 0 will mean that the display is off. A value equal to the
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backlight modulation frequency means full on. The value should not be
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larger than the backlight modulation frequency.
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On displays with a CCFL backlight start from: 0x60016001 To verify if
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all modes work as desired use: `xbacklight -set 10` and gradually
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increase until 100. Displays with an LED backlight need a lower
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backlight modulation. Do the same thing but start from 0x01290129 . Try
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setting different values until you have found a value which presents no
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issue.
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It is important to know that there are four failure modes:
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1. flickering very fast, which could cause epilepsy (frequency is too
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low. decrease divider)
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2. randomly flickering in random intervals - driver IC cannot keep up
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with toggling the mosfet (frequency too fast, increase divider)
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3. frequency is in audible range and causes coils to whine (frequency
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is too high. increase divider)
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4. backlight is uneven. (CCFL specific, frequency is too high. increase
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divider)
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To check for flickering try moving your laptop while looking at it.
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A higher frequency equals higher power consumption. You want to find the
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highest good working value.
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Next this value should be set at boot: either add
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intel_reg write 0x00061254 <your_ideal_value>
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NOTE: on older versions of this utility, use `intel_reg_write` instead.
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before exit 0 in /etc/rc.local or create a systemd service file
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/etc/systemd/system/backlight.service:
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```
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[Unit]
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Description=Set BLC_PWM_CTL to a good value
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[Service]
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Type=oneshot
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RemainAfterExit=no
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ExecStart=/usr/bin/intel_reg write 0x00061254 <your_value>
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[Install]
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WantedBy=multi-user.target
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```
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Now start and enable it:
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sudo systemctl start backlight && sudo systemctl enable backlight
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Special note on i945:
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i945 behaves differently. Bit 16 needs to be 1 and the duty cycle is not
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updated when backlight is changed. There are no available datasheets on
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this target so why it behaves in such a way is not known. So to find a
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working value BLC\_PWM\_CTL set bit 16 to 1 and make sure PWM divider ==
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duty cycle. see <https://review.coreboot.org/#/c/10624/> on bit 16. The
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cause of this issue is that i945, in contrast with to GM45, is set to
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work in BLM Legacy Mode. This makes backlight more complicated since the
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duty cycle is derived from 3 instead of 2 registers using the following
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formula: if(BPC[7:0] <> xFF) then BPCR[15:0] \* BPC[7:0]
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Else BPCR[15:0] BPC is LBB - PCI Backlight Control Register, described
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on <http://www.mouser.com/pdfdocs/945gmedatasheet.pdf> on page 315. BPCR
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is BLC\_PWM\_CTL described in
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<https://01.org/sites/default/files/documentation/g45_vol_3_register_0_0.pdf>
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on page 94. More research needs to be done on this target so proceed
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with care.
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Power Management Beeps on Thinkpads
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===================================
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When disconnecting or connecting the charger, a beep occurs. When the
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battery goes to a critically low charge level, a beep occurs. Nvramtool
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is included in libreboot, and can be used to enable or disable this
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behaviour.
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You need to write changes in a libreboot rom image, and flash it, in order
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to apply them. You can either use a pre-compiled rom image, or create an image
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from the current one in your computer. See here
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<https://libreboot.org/docs/linux/grub_cbfs.html#get-the-rom-image> for
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more information on how to do that.
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Once you have a libreboot rom image, say 'libreboot.rom', you can write
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changes on the image with the following commands.
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Disable or enable beeps when removing/adding the charger:
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sudo ./nvramtool -C libreboot.rom -w power_management_beeps=Enable
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sudo ./nvramtool -C libreboot.rom -w power_management_beeps=Disable
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Disable or enable beeps when battery is low:
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sudo ./nvramtool -C libreboot.rom -w low_battery_beep=Enable
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sudo ./nvramtool -C libreboot.rom -w low_battery_beep=Disable
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You can check that the parameters are set in the image with :
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sudo ./nvramtool -C libreboot.rom -a
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Finally, you need to flash the rom with this new image. See here
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<https://libreboot.org/docs/linux/grub_cbfs.html#with-re-flashing-the-rom>
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for a detailed explanation.
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Get EDID: Find out the name (model) of your LCD panel
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=====================================================
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Get the panel name:
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sudo get-edid | strings
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Or look in `/sys/class/drm/card0-LVDS-1/edid`
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Alternatively you can use i2cdump. In Debian and Devuan, this is in the
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package i2c-tools.
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sudo modprobe i2c-dev
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sudo i2cdump -y 5 0x50 (you might have to change the value for -y)
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sudo rmmod i2c-dev
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You'll see the panel name in the output (from the EDID dump).
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If neither of these options work (or they are unavailable), physically
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removing the LCD panel is an option. Usually, there will be information
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printed on the back.
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e1000e driver trouble shooting (Intel NICs)
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===========================================
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Example error, ¿may happen on weird and complex routing schemes(citation
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needed for cause):
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e1000e 0000:00:19.0 enp0s25: Detected Hardware Unit Hang
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Possible workaround, tested by Nazara: Disable C-STATES.
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*NOTE: this also disables power management, because disabling C-States
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means that your CPU will now be running at full capacity (and therefore
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using more power) non-stop, which will drain battery life if this is a
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laptop. If power usage is a concern, then you should not use this.
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(we're also not sure whether this workaround is appropriate)*
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To disable c-states, do this in Linux:
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```
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for i in /sys/devices/system/cpu/cpu/cpuidle/state/disable;
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do
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echo 1 > $i;
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done
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```
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You can reproduce this issue more easily by sending lots of traffic
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across subnets on the same interface (NIC).
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More information, including logs, can be found on [this
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page](http://web.archive.org/web/20210416010634/https://notabug.org/libreboot/libreboot/issues/23).
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