Various posts in this forum recommend “mem_sleep_default=deep” for increased battery life on the 11th Gen Framework. I also used this setting for years now without problems.
But after updating my BIOS from 3.17 to 3.20, I thought I had bricked my laptop. After putting it to sleep, it would only turn on the fan on high speed, the display would stay black (backlight didn’t turn on), and after 15s or so, would turn off again, only to turn back on after 5s and repeating this forever. Turning it off manually by holding the power button would not help. While it would stay off, the next time I tried to power it on, the same effect happened without me ever being able to boot.
The only way to fix it is resetting the mainboard state by removing the battery and the CMOS battery. The laptop will then show the same effect once (15s high fan speed without backlight), but after turning itself off it will then boot up normally. Phew!
Through trail-and-error I managed to find that this would always happen whenever “mem_sleep_default=deep” is in the kernel command line, and never without. “sleep=deep” alone does not cause the issue.