# Miscellaneous

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- High Pitched Whining Noise on Idle (how to remove in Trisquel 7)
- High Pitched Whining Noise on Idle (how to remove in Parabola)
- X60/T60: Serial port - how to use (for dock owners)
- Power Management Beeps on Thinkpads
- Using diff and patch
- Finetune backlight control on intel gpu’s
- Get EDID: Find out the name (model) of your LCD panel
- How to enable EHCI debugging on the BeagleBone Black

# High Pitched Whining Noise on Idle (how to remove in Trisquel 7)

## Start powertop automatically at boot time

Included with libreboot is a script called 'powertop.trisquel7'. Run this as root and it will setup powertop to run with --auto-tune at boot time. Load the file in your text editor to see how it does that.

$ sudo ./resources/scripts/misc/powertop.trisquel7

Might want to run with --calibrate first

If powertop doesn't work, another way (reduces battery life slightly) is to add processor.max_cstate=2 to the linux line in grub.cfg, using this guide.

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# High Pitched Whining Noise on Idle (how to remove in Parabola)

The following removes most of the noise. It reduces what is a high frequency whine (that not everyone can hear) to a slight buzz (which most people can't hear or doesn't bother most people).

This is not perfect! The full solution is still not discovered but this is a step towards that. Also, in some instances you will need to run 'sudo powertop --auto-tune' again. This needs to be implemented properly in coreboot itself!

On the X60 with coreboot or libreboot, there is a high pitched sound when idle. So far we have use processor.max_cstate=2 or idle=halt in GRUB. These consume power. Stop using them!

Be root
$ su -

Installed powertop:
# pacman -S powertop

and added the following to /etc/systemd/system/powertop.service :

    [Unit]
    Description=Powertop tunings

    [Service]
    Type=oneshot
    RemainAfterExit=no
    ExecStart=/usr/bin/powertop --auto-tune
    # "powertop --auto-tune" still needs a terminal for some reason. Possibly a bug?
    Environment="TERM=xterm"

    [Install]
    WantedBy=multi-user.target

Finally, as root do that:
# systemctl enable powertop
# systemctl start powertop

The next time you boot the system, the buzz will be gone.

Might want to run with --calibrate first

If powertop doesn't work, another way (reduces battery life slightly) is to add processor.max_cstate=2 to the linux line in grub.cfg, using this guide.

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# X60/T60: Serial port - how to use (for dock owners)

For the Thinkpad X60 you can use the "UltraBase X6" dock (for the X60 Tablet it is called X6 Tablet UltraBase). For the ThinkPad T60, you can use the "Advanced Mini Dock".

If you are using one of the ROM images with 'serial' in the name, then you have serial port enabled in libreboot and you have memtest86+ included inside the ROM. Connect your null modem cable to the serial port on the dock and connect the other end to a 2nd system using your USB Serial adapter.

On the 2nd system, you can try this (using GNU Screen):
$ sudo screen /dev/ttyUSB0 115200

How to quit GNU Screen: Ctrl+A then release and press K, and then press Y.

There are also others like Minicom but I like GNU Screen

By doing this before booting the X60/T60, you will see console output from libreboot. You will also see GRUB displaying on the serial output, and you will be able to see MemTest86+ on the serial output aswell. You can also configure your distro so that a terminal (TTY) is accessible from the serial console.

The following guide is for Ubuntu, and can be followed for Trisquel 6.0 which is based on Ubuntu 12.04 (should also work in Trisquel 7, based on Ubuntu 14.04) to enable a serial console using GeTTY:
https://help.ubuntu.com/community/SerialConsoleHowto

Note: part of the tutorial above requires changing your grub.cfg. Just change the linux line to add instructions for enabling getty. See ../gnulinux/grub_cbfs.html.

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# Finetune backlight control on intel gpu’s

Sometimes the backlight control value (BLC_PWM_CTL) set by libreboot is not ideal. The result is either flicker, which could cause nausea or epilepsy or an uneven backlight and/or coil whine coming from the display. To fix this a different value for the gpu reg BLC_PWM_CTL needs to be set. See p94 of https://01.org/sites/default/files/documentation/g45_vol_3_register_0_0.pdf for more information on this reg. The tool for setting registry values on intel gpu’s is included in intel-gpu-tools. Install intel-gpu-tools: sudo apt-get install intel-gpu-tools

You can set values: sudo intel_reg write 0x00061254 <your_value>

The value set has the following structure: bits [31:16] is PWM divider. PWM / PWM_divider = frequency bits [15:0] is the duty cycle and determines the portion of the backlight modulation frequency. A value of 0 will mean that the display is off. A value equal to the backlight modulation frequency means full on. The value should not be larger than the backlight modulation frequency.

On displays with a CCFL backlight start from: 0x60016001 To verify if all modes work as desired use: xbacklight -set 10 and gradually increase until 100. Displays with an LED backlight need a lower backlight modulation. Do the same thing but start from 0x01290129 . Try setting different values until you have found a value which presents no issue.

It is important to know that there are four failure modes:

1. flickering very fast, which could cause epilepsy (frequency is too low. decrease divider)
2. randomly flickering in random intervals - driver IC cannot keep up with toggling the mosfet (frequency too fast, increase divider)
3. frequency is in audible range and causes coils to whine (frequency is too high. increase divider)
4. backlight is uneven. (CCFL specific, frequency is too high. increase divider)

To check for flickering try moving your laptop while looking at it.

A higher frequency equals higher power consumption. You want to find the highest good working value.

Next this value should be set at boot: either add

    intel_reg write 0x00061254 <your_ideal_value>

before exit 0 in /etc/rc.local or create a systemd service file /etc/systemd/system/backlight.service:

    [Unit]
    Description=Set BLC_PWM_CTL to a good value
    [Service]
    Type=oneshot
    RemainAfterExit=no
    ExecStart=/usr/bin/intel_reg write 0x00061254 <your_value>
    [Install]
    WantedBy=multi-user.target

Now start and enable it: sudo systemctl start backlight && sudo systemctl enable backlight

Special note on i945:

i945 behaves differently. Bit 16 needs to be 1 and the duty cycle is not updated when backlight is changed. There are no available datasheets on this target so why it behaves in such a way is not known. So to find a working value BLC_PWM_CTL set bit 16 to 1 and make sure PWM divider == duty cycle. see https://review.coreboot.org/#/c/10624/ on bit 16. The cause of this issue is that i945, in contrast with to GM45, is set to work in BLM Legacy Mode. This makes backlight more complicated since the duty cycle is derived from 3 instead of 2 registers using the following formula: <verbatim> if(BPC[7:0] <> xFF) then BPCR[15:0] * BPC[7:0] Else BPCR[15:0] </verbatim> BPC is LBB - PCI Backlight Control Register, described on http://www.mouser.com/pdfdocs/945gmedatasheet.pdf on page 315. BPCR is BLC_PWM_CTL described in https://01.org/sites/default/files/documentation/g45_vol_3_register_0_0.pdf on page 94. More research needs to be done on this target so proceed with care.

# Power Management Beeps on Thinkpads

When disconnecting or connecting the charger, a beep occurs. When the battery goes to a critically low charge level, a beep occurs. Nvramtool is included in libreboot, and can be used to enable or disable this behaviour.

Disable or enable beeps when removing/adding the charger:
$ sudo ./nvramtool -w power_management_beeps=Enable
$ sudo ./nvramtool -w power_management_beeps=Disable

Disable or enable beeps when battery is low:
$ sudo ./nvramtool -w low_battery_beep=Enable
$ sudo ./nvramtool -w low_battery_beep=Disable

A reboot is required, for these changes to take effect.

# Get EDID: Find out the name (model) of your LCD panel

Get the panel name with sudo get-edid | strings
Or look in /sys/class/drm/card0-LVDS-1/edid

Alternatively you can use i2cdump. In Trisquel, this is in the package i2c-tools.
$ sudo modprobe i2c-dev
$ sudo i2cdump -y 5 0x50 (you might have to change the value for -y)
$ sudo rmmod i2c-dev
You'll see the panel name in the output (from the EDID dump).

If neither of these options work (or they are unavailable), physically removing the LCD panel is an option. Usually, there will be information printed on the back.

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# USB keyboard wakeup on GM45 laptops

Look at resources/scripts/helpers/misc/libreboot_usb_bugfix

Put this script in /etc/init.d/ on debian-based systems.

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