Lenovo T14 Gen 4 – Intel – Suspend/Resume Surprises – Part 4

And on we go with my series on Ubuntu 22.04 support for the Lenovo T14 Gen 4, Intel variant. In this part, I’ll have a closer look at how suspend / resume works when the notebook lid is closed. Spoiler: It works perfectly out of the box, but things are different from what I was used to so far!

Important note: At the end of 2023, Ubuntu 22.04-03 LTS comes with a Linux 6.2 kernel, but I’m using Canonical’s Linux 6.5 OEM kernel, which can be installed via ‘apt’ for proper Wi-Fi support. This might have an influence on suspend/resume as well, but I don’t think so.

One of the first things I always try when I run Linux on a new notebook is if suspend/resume works. That’s a make or break functionality. As I noted before, this works out of the box on the T14 Gen 4, no configuration required. But there’s an interesting twist:

In the past, my Lenovo notebooks typically supported the older ‘suspend to RAM’ (deep) and the newer ‘suspend to idle’ (s2idle) variants. I’ve made good experiences with suspend to RAM over the last decade, and the first notebook that only supported s2idle made me pretty weary of this state, as power consumption on that device during suspend was very high, and the battery was empty in less than a day.

The T14 Gen 4 is also limited to suspend to idle (s2idle) and I have to say that based on my previous experience, I was not amused about that at first. The battery being sucked dry in less than a day while in suspend state is not acceptable. But to my big surprise, the s2idle implementation of the T14 Gen 4 in combination with a Linux 6.5 kernel is perfect! When closing the lid, the fan will still keep running if the system is hot. I’ve never had that before on any other notebook, so I was a bit unsure if this is a good thing. But once the fan stops, power consumption of the system while the lid is closed goes down to almost 0.

I let the notebook stay in suspend state overnight for 14 hours, and when I came back, the battery charge state had only decreased by 9%. In other words, less than 1% per hour, which is significantly better than the 25-30% of my X13 in ‘deep’ suspend state over 12 hours. I repeated the exercise a number of times and always ended up with the same good result. An interesting and most welcome surprise!