$ dmesg
....
[    4.950114] i915 0000:00:02.0: firmware: failed to load i915/skl_dmc_ver1_27.bin (-2)\\
[    4.950118] firmware_class: See https://wiki.debian.org/Firmware for information about missing firmware
....

$ sudo apt install firmware-misc-nonfree

$ dmesg
....
[    0.032301] [Firmware Bug]: TSC_DEADLINE disabled due to Errata; please update microcode to version: 0xb2 (or later)
....

$ sudo apt install intel-microcode