s2idle-nature-laptops: new post

Author: ariadnavigo

content/posts/s2idle-nature-laptops.md

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+title = "S2idle and the Nature of Laptops"
+date = '2025-07-18T01:20:18+02:00'
+author = "Ariadna"
+tags = ["linux", "hardware", "my stories", "history"]
+keywords = ["s0ix", "acpi", "linux", "hardware", "sleep states"]
++++
+
+You tell your laptop to "suspend to RAM." Are you really sure that's what your
+system just did? I was utterly surprised, when I purchased my current laptop (a
+model of the HP 15 series that was released in 2024), that _things had changed_
+since the last laptop I had bought back in 2013.[^1] Power management has
+changed, and things smell a lot of "mobile convergence" these days.
+
+It's funny because using Linux shields you from one day discovering that your
+10 years old PC doesn't work anymore. Linux supports old systems by philosophy,
+where MacOS and Windows are picky about how old your laptop, especially laptops,
+is. Microsoft is more lenient on the software side of things, such that only
+until recently you still could run old Win16 software on modern Windows
+versions. When it comes to hardware, though, good luck if your system doesn't
+come with UEFI and "certified" hardware, and good luck in a couple of years.
+
+So, while my old ASUS X55C had the power management features of a laptop from
+2013, this HP 15 showed me that... even "sleep" had changed. I'm not sure how I
+noticed that something was different; I guess it was the fact that waking up
+from "sleep" was super fast on this new laptop, with almost no time delay when
+it came to reconnect to WiFi or Bluetooth. I immediately knew where to look at
+and I was presented with something I had never met before:
+
+```bash
+$ cat /sys/power/mem_sleep 
+[s2idle]
+```
+
+In the old days of regular ACPI S3 sleep, you would've seen a couple of
+different options, like ``shallow`` and ``deep``, the latter being what we would
+usually call _Suspend to RAM_ or "actual" S3. The ``shallow`` setting is for
+_Suspend to standby._ For more details about what all of this means, there's
+[documentation available][sleep-docs] from the Linux kernel itself explaining
+everything in detail.
+
+The way the sysfs files for power management work is interesting. Files under
+``/sys/power`` only show power states that your system _supports._ That
+information, obviously, comes from the firmware itself. Therefore, if I tried
+something like the following on **my** computer to put it to sleep into an 
+actual, traditional S3 state that powers everything off except for the RAM...
+
+```bash
+# echo 'deep' > /sys/power/mem_sleep
+bash: echo: write error: Invalid argument
+```
+
+So, my new laptop only supports a sleep state that is implemented somewhere in
+the motherboard (the UEFI?). The important bit about S0ix/s2idle states is that
+there are different levels, beyond the one that is equivalent to _suspend to
+RAM;_ you actually may enter a S0i1 state just by having your laptop sitting
+idle with the screen off: some parts of the motherboard may enter a low-power
+state, some not... Deeper S0ix states will power down more parts of the hardware
+or make them enter deeper low-power states. Of course, this requires the Linux
+kernel to support requesting these states to the firmware.
+
+If this sounds oddly familiar to how smartphones manage power, bingo. Although
+smartphones, as far as I know do not follow ACPI specifications, the behavior is
+practically the same. When you leave your smartphone sitting idle, it selective
+powers down components to save energy. On Android, this is called
+[Doze.][android-doze]
+
+You know what else has happened to laptops in the last couple of years? I
+noticed this when I got this new one. They're significantly harder to extend, to
+open up, etc., if not straight impossible. I can't even upgrade the RAM on this
+one. It's a sealed box, meant to stay as is since it was shipped from the
+factory. If you have the skills to get inside it, you may do so, but it is not
+meant to be opened. My old laptop, and any old laptop, at least allowed you to
+change some components: I had replaced my old ASUS's spinning hard drive with a
+SATA SSD drive, extended its RAM with a pair of extra modules, and replaced its
+battery pack. All three upgrades or repairs are _hardly possible_ on this new HP
+15.
+
+There are many reasons why we got into this situation, Apple being an important
+part of it (I guess), but there's also another side to this. If you, the vendor,
+can predict that the hardware _will_ stay the same, then you are able to
+implement coherent power management to all components the laptop ships with. One
+of the issues with traditional S3 sleep, or even S4 (_Suspend to disk,_ aka
+"hibernation"), was that many times hardware components entered undefined states
+when woken up. This wasn't even a problem exclusive to Linux: this could happen
+to you on Windows as well. The reason behind this is obvious: the platform was
+open, you couldn't predict whether the user was going to change or upgrade
+something that would break when entering a sleep state because of drivers or
+your firmware not being able to handle that new component correctly.
+
+I'm under the impression that a modern laptop is much closer to a smartphone 
+than to a desktop workstation. We're still on a version of x86 that internally 
+complies with the PC standard, but laptops have evolved to behave much more like
+our ARM-based smartphones. My HP 15 is practically a big tablet running Arch
+Linux. And you know what? There are improvements to take into account from this
+historical evolution.
+
+I no longer suspend to disk. I know this laptop will _reliable_ wake up every
+single time I ask it to suspend _to idle._ I know my WiFi and Bluetooth cards
+will resume operations immediately as soon as I wake the system up. I know there
+will be no graphical gitches or slow-downs either (I was plagued with these on
+my old ASUS, thanks to the infamous i915 driver). I'm not even getting into the
+improvements in battery life that come from smart charging and discharging
+implemented in UEFI and modern power supplies.[^2] Suspending to disk was sort
+of a workaround I used to save power and time, but also had its own issues
+(again, the i915 driver, but sometimes also networking). Now, with this new 
+machine, I know things will work out of the box (unless some kernel update
+breaks something, which is unlikely).
+
+Convenience is mostly always good, unless it comes with ethical problems [like
+generative AI does]({{< ref "posts/ai-not-friend-not-therapist" >}}). Of course,
+everyone's definition of _convenience_ will be different. Arch Linux is
+convenient for me, but you might find Ubuntu more convenient. We all love
+tinkering and I guess we all also love the thrill (and frustration) of fixing an
+unexpected issue on our computers, but in the end of the day, we use these
+machines _to get things done._ And I'm someone who wants her computer to be up
+and running as fast as possible from a sleep state because I might want to write
+down an idea on a text editor and close the lid a minute later.
+
+I understand the problems with closing down the platforms we use daily, though.
+I'm also nostalgic of the past where PCs were your hardware playground. Laptops
+were always more closed down than desktop PCs, but still. However, I do wonder
+whether we were compensating for the shortcomings of the industry back in the
+90s and 00s. Gravis, from the [_Cathode Ray Dude_ YouTube channel,][crd-yt] has
+repeatedly stated that the PC platform has become a "solved problem" in the last
+decade or so. There are no weird hardware experiments like [strange PCMCIA
+cards,][crd-pcmcia-camera] peripherals have all converged into USB devices
+(maybe HDMI is the only standing exception), WiFi has become practically
+universal (this laptop does _not_ have an Ethernet port), we have gotten rid of
+SD cards and other external storage devices... I am surprised that my new laptop
+comes with a headphone jack. The PC in general, but probably laptops even more,
+have become "boring." This is the price of having figured a technology out, I
+guess.
+
+[^1]: I tried to extend its life as much as I could, but after 11 years of many
+    repairs, changed parts, that old ASUS X55C was in no shape to be my main
+    system at all. It was a sad goodbye, because I wrote my PhD thesis on it,
+    and we had endured many, many adventures together.
+
+[^2]: Have you noticed the data pin living inside the DC connector?
+
+[sleep-docs]: https://www.kernel.org/doc/html/latest/admin-guide/pm/sleep-states.html
+
+[android-doze]: https://source.android.com/docs/core/power/platform_mgmt
+
+[crd-yt]: https://www.youtube.com/@CathodeRayDude
+
+[crd-pcmcia-camera]: https://www.youtube.com/watch?v=xpJBHjl9_VU