Which model of XPS 13? There have been so many different ones over the years.
And what is real sleep mode? Suspend to disk?
And what is real sleep mode? Suspend to disk?
Not even that. Suspend to RAM is gone. It was perfectly fine, until someone had this great idea that PCs should behave like cellphones: just turn the screen off, meanwhile stay awake and connected. Hopefully it means doing the minimum necessary to receive and notify emails, but in practice this means the laptop will decide it's time to run the antivirus scan, do your scheduled backup and perform all kinds of maintenance right when your laptop is in your backpack and you're on your way to work. Microsoft calls it Modern Standby. I think there's also a degree of pushing on the manufacturers' side, as it's not purely an OS thing: sleep states must be enabled at the BIOS level for the OS to use them. Lenovo allows enabling the "legacy" sleep state, Dell does not.
See the previous shitstorm here: https://news.ycombinator.com/item?id=28646776
As far as I know, it's still no less of an issue to this day.
https://martinpoehlmann.com/posts/tech/2021-07-30-dell-s3-mo...
https://libreddit.privacydev.net/r/Dell/comments/h0r56s/gett...
And I don't want it to be able to wake up from this or do anything unless I press a button.
These days we have "modern standby" instead, which keeps all things powered somewhat to allow for a quick wakeup by notifications for example. Just like your mobile phone. In theory, at least.
How do I check (from Linux) if the laptop can go into suspend to memory or not?
I think `cat /sys/power/mem_sleep` should tell you the desired modes; the active mode is selected and iirc changing one is done by writing the name of an option into the file. There are some related files next to `mem_sleep` in `/sys/power/`.
If you are moderately lucky, you may not have this _yet_, but you get it with a BIOS update.
But even if you have it, Linux might be hit and miss - sometimes it works, sometimes not, usually crippling some device like the touchpad after a wake-up.
You can try `cat /sys/power/mem_sleep` to see what states you have available. "deep" is what you want. "s2idle" and "shallow" are the ones that are just "low-power".
EDIT: actually, after a bit of web browsing it turns out that Intel 11th gen and above do not have S3 support anymore. So don't wait for BIOS support, it won't happen...
Would switching to an AMD laptop fix it?
Strange, that KDE still writes "Suspend to RAM" under the "Sleept" button when it cannot do that.