How to compile and install the latest linux Kernel on Debian 11

The default Kernel on Debian 11 bullseye is 5.10. In this guide, we want to upgrade to linux kernel 5.16.

Why?

The new Kernel 5.16 includes rtw89 wifi drivers for Realtek 8852AE 802.11ax PCIe wireless network adapter found on some Lenovo ThinkPad laptops (ThinkPad L14 gen1). This kernel upgrade will also fix bluetooth problems with the same wireless chip.

Disclaimer

Use this guide at your own risk! Please backup everything before you begin.

Instructions

Verify the Kernel version on your system with uname:

$ uname -r
5.10.0-11-amd64

Install required packages and update your system:

$ sudo apt update
$ sudo apt install wget build-essential dwarves python3 libncurses-dev flex bison libssl-dev bc libelf-dev
$ sudo apt upgrade

Download official firmware for Realtek 8852AE

$ sudo mkdir /lib/firmware/rtl_bt/
$ cd /lib/firmware/rtl_bt
$ sudo wget https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/plain/rtl_bt/rtl8852au_config.bin
$ sudo wget https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/plain/rtl_bt/rtl8852au_fw.bin
$ sudo mkdir /lib/firmware/rtw89/
$ cd /lib/firmware/rtw89
$ sudo wget https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/plain/rtw89/rtw8852a_fw.bin

Download the latest Kernel source code with wget and extract it:

$ cd /usr/src/
$ sudo wget https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.16.5.tar.xz
$ sudo tar xvf linux-5.16.5.tar.xz
$ cd linux-5.16.5/

Copy your current Kernel's configuration file (Debian stock Kernel config):

$ sudo cp -v /boot/config-$(uname -r) .config

Create a new config based on your current config (you can hit enter till the end):

$ sudo make oldconfig

Load the tool to configure the linux source:

$ sudo make menuconfig

Make sure to add Realtek 802.11ax 8852AE drivers, and to save the new config, you can find the drivers here:

- device drivers
-- network device support
--- wireless lan
---- realtek devices -> realtek 802.11ax -> 8852AE

Fix potential signing errors by setting this in your .config (or set your own keys):

CONFIG_SYSTEM_TRUSTED_KEYS=""

Now compile the Kernel (this will take some time, you can speed it up by using the make in parallel mode with -j flag, for example make -j4 to use 4 cores):

$ sudo make clean
$ sudo make bzImage

Install modules:

$ sudo make modules
$ sudo make modules_install

Strip unnecessary files to reduce the size of initrd and /lib/modules/5.16.5/ directory:

$ sudo find /lib/modules/5.16.5/ -name *.ko -exec strip --strip-unneeded {} +

Next, install the compiled Kernel:

$ sudo make install

The command will install the files below in the /boot/ directory:

vmlinuz-5.16.5
initramfs-5.16.5.img
System.map-5.16.5

Optional, configure GRUB to remeber the last Kernel selected. Open /etc/default/grub and put the following in:

GRUB_DEFAULT=saved
GRUB_SAVEDEFAULT=true

For the changes made to take place, we need to update GRUB and reboot:

$ sudo update-grub
$ sudo reboot now

Credits

Thanks to all who figured this out and posted useful bits of info around the web. Enjoy!