[SOLVED] KDE freezes on startup on laptop

[juantxorena]

Hello,

I have a nasty bug with KDE in my new laptop. As the title says, it completely freezes after a couple of minutes from login. It's a hard freeze, the keyboard stops working (even the caps lock light), SysRq doesn't work, etc. I have to turn it off pressing the power button for 5 seconds.

The thing is that some days ago it worked perfectly. I had some problems with brightness control and some other acpi-related stuff, so I had to add the following stuff in grub for the kernel:
"acpi_osi=linux acpi_backlight=vendor pcie_asm=force". After doing that, I was able to use it perfectly and even hibernate it. It was since I rebooted it from the hibernation when I started to have problems. First when unplugging and plugging the power cord to try some power-saving things, or so I thought, because then it started to freeze just for being logged in. If I leave the kdm screen without login, or I stop the x server and use the console, nothing happens, I can use it as usual, so it's a kde thing.

Nothing shows in xorg.0.log, dmesg, /var/log/messages, xsession-errors or any other relevant thing that I can think about.

It has occurred to me right now while I'm writing this that may be related to some power-saving feature that activates after a couple of minutes. I'm at work right now and don't have the laptop, but I can try it later.

Edit: I forgot to say that I've tried to remove pcie_asm=force after reading that it may cause some stability problems, but the same thing happens.
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I cannot write English very well. Please, correct any mistake so that I can improve.

[juantxorena]

It turns out it was backlight related. My laptop is a dell one, and I was missing "dell_laptop.backlight=0" in grub for the kernel.Which,BTW, it isn't documented anywhere, I found that in an obscure forum for some guy with a similar problem.
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I cannot write English very well. Please, correct any mistake so that I can improve.