Restoring S3 Suspend to X1 Carbon (6th Gen) on Linux

My current laptop is the second in the X1 Carbon lineup I’ve owned. In general, it’s been painless running Linux. However, in this current iteration, I was surprised to find that suspend-to-ram functionality isn’t enabled in UEFI. Apparently, Lenovo is catering to a new Microsoft sleep state Windows Modern Standby that allows for devices to be more easily woken up when in deep sleep (think mobile phones). There’s a long thread on the Arch forums about this, and I was able to successfully follow this blog post in order to patch my system, with a few exceptions.

When applying the patch with the following command

patch --verbose < X1C6_S3_DSDT.patch

Hunk #7 failed to apply.

Looking at the patch itself, this is an easy removal of two lines, and I was able to complete the patch by hand without issue.

@@ -415,9 +351,7 @@
     Name (SS1, 0x00)
     Name (SS2, 0x00)
     Name (SS3, One)
-    One
     Name (SS4, One)
-    One
     OperationRegion (GNVS, SystemMemory, 0xAB54E000, 0x0767)
     Field (GNVS, AnyAcc, Lock, Preserve)
     {systemd-boot

The instructions to path also are specific to Grub, however, getting things working with systemd-boot was pretty easy. I followed the Arch wiki when installing, and my system boots from an entry located in /boot/entries/arch.conf. Updating this configuration to map the patched ACPI table into memory on boot required as single additional initrd declaration.

initrd /intel-ucode.img
initrd /acpi_override
initrd /initramfs-linux.img

Modifying the default suspend mode required adding an additional kernel flag to the end of the options declaration.

options quiet rw intel_pstate=no_hwp mem_sleep_default=deep

After rebooting, everything works, and I can suspend the system with systemctl suspend -i or closing the lid. While I’ve found battery life on Linux to be a bit worse than Windows, the ability to close the lid and go into deep sleep makes such a huge difference when taking a laptop to a cafe or on a trip without have to constantly shutdown and restart the system. Hopefully this will be patched in a future BIOS from Lenovo, but the patch itself was very easy and well document, even though it’s always a little scary to have to get your hands dirty.