# gentoo on dell xps 15" 4K touchscreen unstable

## alvinwu

Dear friends, I recently install gentoo on the Dell XPS 15: 4K touch screen laptop, dual boot with the pre-installed Win10.

And with many trial to configure the kernel (gentoo-sources 4.2.8 & 4.3.3), with kernel 4.2.8, the machine starts but occasionally hangs, and cannot boot up with a readable screen with kernel 4.3.3 (the screen is dark, sometime it can show up after suspend / wakeup events..but the laptop still hangs quickly.)

Can someone show me the proper kernel configuration for this laptop?

Thanks!

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## Keruskerfuerst

Can you try to use a live cd/dvd like Systemrescuecd, Ubuntu or different?

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## alvinwu

I actually also installed Ubuntu 15.10 on the laptop, booting with Ubuntu didn't hang but sometimes will have weird touchpad issues, such as non responsive, or over reacted, I can see the windows maximize and normalize (...the windows size...) automatically, (...that is uncontrollable...)

I then copy the whole ubuntu kernel config into the gentoo-sources tree, and also creates relevant modules blacklist entries since that config is almost everything . And then the result is unstable... 

Now I'm trying to fine tune the config, and also tests for kernel 4.3.3 as well.

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## Keruskerfuerst

Where are the routines for the acess to the touchscreen programmed?

I don´t think it is the kernel.

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## alvinwu

I try the git-sources-4.4.0-rc6 and that works with some minor issues, I had to temporarily blacklist the nouveau module during boot, with the kernel command option "modprobe.blacklist=nouveau".

Then "modprobe nouveau" after I login to the Gnome, otherwise the keyboard/mouse behave strangely. 

Now I work with it for couples of hours, major functions are working now. I shall update about the result with more testings for at least couples of days. Great Gentoo platform for the flexibility, customizable and great performance!  

Appreciate anyone could share your suggestions for any enhancements.

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## alvinwu

Upon running couple of days with gentoo-sources 4.4.0 kernel and removing all sorts of preset modules options, major functions are working properly with the following minor problem:

1. occasionally (very seldom) power off freeze, I have to hard press the power button in order to turn that off.

2. occasionally (very seldom) GDM screen doesn't shows up, becomes a dark screen and the machines freeze.

3. brightness response sluggish, the gnome brightness pop-up window delays about 1 to 2 seconds after I press the buttons, and obviously slow down the whole system, just like every tasks have to wait for that brightness change completes.  

4. /sys/kernel/debugs/vgaswitcheroo/switch doesn't work, dmesg shows "vga_switcheroo: client 0 refused switch" when trying to switch to DIS.

 *Quote:*   

> 
> 
> cat /sys/kernel/debug/vgaswitcheroo/switch 
> 
> 0:IGD:+:Pwr:0000:00:02.0
> ...

 

Several dmesg error/warning messages:

1. 

 *Quote:*   

> 
> 
> [    7.499019] nouveau 0000:01:00.0: DRM: VRAM: 2048 MiB
> 
> [    7.499020] nouveau 0000:01:00.0: DRM: GART: 1048576 MiB
> ...

 

2.

 *Quote:*   

> 
> 
> [    8.689718] [drm:intel_dp_link_training_channel_equalization [i915]] *ERROR* 5.4 Gbps link rate without HBR2/TPS3 support
> 
> 

 

3.

 *Quote:*   

> 
> 
> [  439.335881] nouveau 0000:01:00.0: DRM: evicting buffers...
> 
> [  439.335890] nouveau 0000:01:00.0: DRM: waiting for kernel channels to go idle...
> ...

 

Appreciate anyone suggests enhancements.

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## Keruskerfuerst

THe touchscreen must be calibrated.

Try to search or contact dell in that case.

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## alvinwu

It becomes more stable with recent kernel source gentoo-4.4.2 and git-4.5.0-rc5, so I consider the problem is solved although I have not test the bluetooth & external HDMI monitor.

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## alvinwu

Sovled.

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