Got the same issue on my HP ZBook Studio G5 x360 with a Nvidia Quadro P1000 (Mobile) GPU using the proprietary nvidia drivers on kernel 4.17.9-1-ARCH, the workaround of setting kernel options to 'acpi_osi=! acpi_osi="Windows 2009"' works.
Got the same issue on my HP ZBook Studio G5 x360 with a Nvidia Quadro P1000 (Mobile) GPU using the proprietary nvidia drivers on kernel 4.17.9-1-ARCH, the workaround of setting kernel options to 'acpi_osi=! acpi_osi="Windows 2009"' works.