S3 deep sleep for Lenovo yoga X1 3rd Generation on Fedora 28

acpi_yogaX1_fedora28

This is a step-by-step guide on how make sleep mode work with a Lenovo Yoga X1 3rd generation running Fedora 28 (UEFI based system).
Kernel version: 4.17.4-200.fc28.x86_64

Credits: most of this guide comes from `https://delta-xi.net/#056`. The patch I used is a little different though, taken from http://kernel.dk/acpi.patch 
(found through https://bbs.archlinux.org/viewtopic.php?pid=1794150#p1794150), and some of the steps slightly differ as well as mine is a UEFI based system.

1. Reboot, enter BIOS/UEFI. Go to Config - Thunderbolt (TM) 3 - set Thunderbolt BIOS Assist Mode to Enabled. Set also Security - Secure Boot to Disabled.

2. Install iasl (Intel's compiler/decompiler for ACPI machine language) and cpio: `sudo yum install acpica-tools cpio`

3. Get a dump of ACPI DSDT table:   `cat /sys/firmware/acpi/tables/DSDT > dsdt.aml`

4. Decompile the dump, which will generate a `.dsl` source based on the `.aml` ACPI machine language dump: `iasl -d dsdt.aml`

5. Download the [patch](http://kernel.dk/acpi.patch) and apply it against `dsdt.dsl`: `patch --verbose < acpi.patch`

Hunk 2 failed for me, I manually looked for the following in `dsdt.dsl`:

```
    Name (SS1, 0x00)
    Name (SS2, 0x00)
    Name (SS3, One)
    One
    Name (SS4, One)
    One
```

and replaced it with the following (removing the two "One" lines):

```
    Name (SS1, 0x00)
    Name (SS2, 0x00)
    Name (SS3, One)
    Name (SS4, One)
```

6. Recompile your patched version of the .dsl source: `iasl -ve -tc dsdt.dsl`

7. Create a CPIO archive with the correct structure, which GRUB can load on boot. We name the final image `acpi_override` and copy it into `/boot/`:

```
  mkdir -p kernel/firmware/acpi
  cp dsdt.aml kernel/firmware/acpi
  find kernel | cpio -H newc --create > acpi_override
  cp acpi_override /boot
```

8. GRUB needs to boot the kernel with a parameter setting the deep sleep state as default. Edit `/etc/default/grub` and add the following:

```
  GRUB_CMDLINE_LINUX_DEFAULT="mem_sleep_default=deep"
```
  
9. Regenerate the GRUB configuration: `grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg`
 
10. Tell GRUB to load the new DSDT table on boot in its configuration file located in `/boot/efi/EFI/fedora/grub.cfg`. Find the relevant GRUB menu entry 
and add the new image (`/acpi_override`) to the `initrdefi` line:

```
initrdefi /acpi_override /initramfs-4.17.4-200.fc28.x86_64.img
```

Note: This step needs to be repeated every time the kernel is upgraded and the GRUB configuration is rewritten. Ideally this step would not be needed as
we could instead add `GRUB_EARLY_INITRD_LINUX_CUSTOM="/acpi_override"` to `/etc/default/grub` as part of step 8 which would survive upgrades. 
But such line is currently ignored by fedora, see https://bugzilla.redhat.com/show_bug.cgi?id=1600414.
 
10. Reboot and enjoy having a laptop running Linux again... close the lid and the battery does not get drained in a few hours, also the battery no longer stays warm in sleep mode.

To verify that things are working:

```
dmesg | grep ACPI | grep supports
#[    0.195933] ACPI: (supports S0 S3 S4 S5)
cat /sys/power/mem_sleep
#s2idle [deep]
```