Lenovo Yoga C940

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Hardware Lenovo Yoga C940

on linux-5.7.5 kernel

Laptop Specifications

Device Model Works Notes
Intel® Core™ i7 Intel Core i7-1065G7 CPU @ 1.30GHz Yes
Graphics Intel® HD Iris Plus G7 Yes
Screen 13.3", 3840×2160, 16:9 aspect ratio Yes
WiFi card Intel Corporation Killer Wi-Fi 6 AX1650i 160MHz Wireless Network Adapter (201NGW) Yes
Bluetooth Yes
Audio Lenovo Smart Sound Technology Audio Controller Yes Needs a BIOS update as documented in linux#205755, and possibly gentoo-sources≥5.10.10
Camera Yes
Touchscreen Wacom tablet with a Pen Yes multitouch ok
Touchpad Yes multitouch support: two finger scrolling: ok, tap click & tap drag: ok, left and right click: ok

Configuration details

Host bridge

root #lspci -nn -k
00:00.0 Host bridge [0600]: Intel Corporation Device [8086:8a12] (rev 03)
        Subsystem: Lenovo Device [17aa:3801]
        Kernel driver in use: icl_uncore
KERNEL 
.config - Linux/x86 4.9.95-gentoo Kernel Configuration
 →

Graphics

Works using x11-drivers/xf86-video-intel with VIDEO_CARDS="intel i965 iris".

See Intel.

PCIe bus

root #lspci -nn -k
00:07.0 PCI bridge [0604]: Intel Corporation Ice Lake Thunderbolt 3 PCI Express Root Port #0 [8086:8a1d] (rev 03)
        Kernel driver in use: pcieport
00:07.1 PCI bridge [0604]: Intel Corporation Ice Lake Thunderbolt 3 PCI Express Root Port #1 [8086:8a1f] (rev 03)
        Kernel driver in use: pcieport

USB Bus

root #lspci -nn -k
00:0d.0 USB controller [0c03]: Intel Corporation Ice Lake Thunderbolt 3 USB Controller [8086:8a13] (rev 03) 
       Subsystem: Lenovo Ice Lake Thunderbolt 3 USB Controller [17aa:380a]
Kernel driver in use: xhci_hcd

Thunderbolt

root #lspci -nn -k
00:0d.2 System peripheral [0880]: Intel Corporation Ice Lake Thunderbolt 3 NHI #0 [8086:8a17] (rev 03) 
       Kernel driver in use: thunderbolt
Kernel modules: thunderbolt

NVMe SSD

root #lspci -nn -k
55:00.0 Non-Volatile memory controller [0108]: Samsung Electronics Co Ltd NVMe SSD Controller SM981/PM981/PM983 [144d:a808] 
       Subsystem: Samsung Electronics Co Ltd NVMe SSD Controller SM981/PM981/PM983 [144d:a801]
Kernel driver in use: nvme

Display

Worked out-of-the box in X.

Wireless

root #lspci -nn -k
00:14.3 Network controller [0280]: Intel Corporation Killer Wi-Fi 6 AX1650i 160MHz Wireless Network Adapter (201NGW) [8086:34f0] (rev 30) 
       Subsystem: Intel Corporation Killer Wi-Fi 6 AX1650i 160MHz Wireless Network Adapter (201NGW) [8086:0074]
Kernel driver in use: iwlwifi

Audio

root #lspci -nn -k
00:1f.3 Multimedia audio controller [0401]: Intel Corporation Smart Sound Technology Audio Controller [8086:34c8] (rev 30) 
       Subsystem: Lenovo Smart Sound Technology Audio Controller [17aa:382e]
       Kernel driver in use: sof-audio-pci
Kernel modules: snd_hda_intel, snd_sof_pci

bluetooth

root #lsusb -t
/:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/12p, 480M
    |__ Port 10: Dev 7, If 0, Class=Wireless, Driver=btusb, 12M
    |__ Port 10: Dev 7, If 1, Class=Wireless, Driver=btusb, 12M
KERNEL 
.config - Linux/x86 4.9.95-gentoo Kernel Configuration
 → Search (CONFIG_BT_HCIBTUSB) 

 Symbol: BT_HCIBTUSB [=m]
 Type  : tristate
 Prompt: HCI USB driver
 Location:
  │     -> Networking support (NET [=y])  
  │       -> Bluetooth subsystem support (BT [=m])│  
  │ (1)     -> Bluetooth device drivers│  
  │   Defined at drivers/bluetooth/Kconfig:21│  
  │   Depends on: NET [=y] && BT [=m] && USB [=y]│  
  │   Selects: BT_INTEL [=m]

Could pair with a bluetooth headset

Bluetooth — describes the configuration and usage of Bluetooth controllers and devices.

misc

root #lspci -nn -k
00:04.0 Signal processing controller [1180]: Intel Corporation Device [8086:8a03] (rev 03)
        Subsystem: Lenovo Device [17aa:3802]
        Kernel driver in use: proc_thermal
        Kernel modules: processor_thermal_device
00:12.0 Serial controller [0700]: Intel Corporation Device [8086:34fc] (rev 30)
        Subsystem: Lenovo Device [17aa:384d]
        Kernel driver in use: intel_ish_ipc
        Kernel modules: intel_ish_ipc
00:14.2 RAM memory [0500]: Intel Corporation Device [8086:34ef] (rev 30)
        Subsystem: Lenovo Device [17aa:3846]
00:16.0 Communication controller [0780]: Intel Corporation Management Engine Interface [8086:34e0] (rev 30)
        Subsystem: Lenovo Management Engine Interface [17aa:383a]
        Kernel driver in use: mei_me
00:1f.0 ISA bridge [0601]: Intel Corporation Ice Lake-LP LPC Controller [8086:3482] (rev 30)
        Subsystem: Lenovo Ice Lake-LP LPC Controller [17aa:380e]
00:1f.4 SMBus [0c05]: Intel Corporation Ice Lake-LP SMBus Controller [8086:34a3] (rev 30)
        Subsystem: Lenovo Ice Lake-LP SMBus Controller [17aa:3811]
        Kernel driver in use: i801_smbus
        Kernel modules: i2c_i801
00:1f.5 Serial bus controller [0c80]: Intel Corporation Ice Lake-LP SPI Controller [8086:34a4] (rev 30)
        Subsystem: Lenovo Ice Lake-LP SPI Controller [17aa:3812]
Note
https://www.kernel.org/doc/Documentation/misc-devices/mei/mei.txt Intel Management Engine (Intel ME) is an isolated and protected computing resource (Co-processor) residing inside certain Intel chipsets.

Touchpad and TouchScreen

root #lspci -nn -k
00:15.0 Serial bus controller [0c80]: Intel Corporation Ice Lake-LP Serial IO I2C Controller #0 [8086:34e8] (rev 30)
        Subsystem: Lenovo Ice Lake-LP Serial IO I2C Controller [17aa:3840]
        Kernel driver in use: intel-lpss
        Kernel modules: intel_lpss_pci
00:15.1 Serial bus controller [0c80]: Intel Corporation Ice Lake-LP Serial IO I2C Controller #1 [8086:34e9] (rev 30)
        Subsystem: Lenovo Ice Lake-LP Serial IO I2C Controller [17aa:3841]
        Kernel driver in use: intel-lpss
        Kernel modules: intel_lpss_pci
00:15.2 Serial bus controller [0c80]: Intel Corporation Ice Lake-LP Serial IO I2C Controller #2 [8086:34ea] (rev 30)
        Subsystem: Lenovo Ice Lake-LP Serial IO I2C Controller [17aa:3842]
        Kernel driver in use: intel-lpss
        Kernel modules: intel_lpss_pci

webcam

Note
todo

driver summary

Note
todo

Problems & Workarounds

Thermal shutdowns

It seems that one temperature sensor is not taken into account properly when throttling the CPU. This leads to frequent thermal shutdowns when under high load, especially when the battery is being charged.

Solution for now:

  1. Install sys-power/thermald and add it to the default runlevel
  2. Put the following custom configuration into /etc/thermald/thermald-conf.xml
FILE /etc/thermald/thermald-conf.xml
<?xml version="1.0"?> 
<ThermalConfiguration> 
<Platform>
        <Name> Auto generated </Name>
        <ProductName>81Q9</ProductName>
        <Preference>QUIET</Preference>
        <PPCC>
                <PowerLimitIndex>0</PowerLimitIndex>
                <PowerLimitMinimum>12000</PowerLimitMinimum>
                <PowerLimitMaximum>23000</PowerLimitMaximum>
                <TimeWindowMinimum>28000</TimeWindowMinimum>
                <TimeWindowMaximum>32000</TimeWindowMaximum>
                <StepSize>500</StepSize>
        </PPCC>
        <ThermalZones>
                <ThermalZone>
                        <Type>auto_zone_0</Type>
                        <TripPoints>
                                <TripPoint>
                                        <SensorType>SEN2</SensorType>
                                        <Temperature>63000</Temperature>
                                        <Type>Passive</Type>
                                        <CoolingDevice>
                                                <Type>B0D4</Type>
                                                <SamplingPeriod>8</SamplingPeriod>
                                                <TargetState>2147483647</TargetState>
                                        </CoolingDevice>
                                </TripPoint>
                                <TripPoint>
                                        <SensorType>SEN2</SensorType>
                                        <Temperature>64000</Temperature>
                                        <Type>Passive</Type>
                                        <CoolingDevice>
                                                <Type>B0D4</Type>
                                                <SamplingPeriod>8</SamplingPeriod>
                                        </CoolingDevice>
                                </TripPoint>
                                <TripPoint>
                                        <SensorType>SEN4</SensorType>
                                        <Temperature>74000</Temperature>
                                        <Type>Passive</Type>
                                        <CoolingDevice>
                                                <Type>B0D4</Type>
                                                <SamplingPeriod>8</SamplingPeriod>
                                        </CoolingDevice>
                                </TripPoint>
                        </TripPoints>
                </ThermalZone>
        </ThermalZones>
</Platform>
</ThermalConfiguration>

This is the configuration provided by the firmware plus an entry for SEN4 which is responsible for most of the shutdowns on my system.

HiDPI

Set global scaling in your desktop configuration. For KDE this can be found right below the display configuration.

With X it was impossible to have different scaling factors per monitor, which makes external monitors hard to use unless they have similar resolution.

I have a somewhat working setup now with Plasma 5.19 / KDE 20.04 and wayland.


Screen rotation

Seems to be unstable with Plasma 5.19.


Sounds

Out of the box only the sound bar works (fixed by the BIOS update below). Some users have reported additional issues:

  • Sound doesn’t work entirely. → This is usually an issue with the kernel configuration and missing modules.
  • The headphone jack doesn’t deliver bass (as reported in the sof-project). This is also fixed by the BIOS update below.

As of February 2021 there is a patched BIOS image (customized version 57 provided by Lenovo staff) that fixes the issue with the speakers. Check out kernel bug comments and Lenovo forum thread for details and instructions.

After the BIOS upgrade audio has been confirmed to work on recent Gentoo using 5.10.10+ kernel version (this author used 5.10.10 and no special settings).

Automatic screen rotation

Didn’t look into it yet.

External resources

Retrieved from "https://wiki.gentoo.org/index.php?title=Lenovo_Yoga_C940&oldid=1295359"