xps9350: touchscreen stops working after sleep

Same problem for me - on 16.04.

Apparently (I haven't tested), your fix works with kernel 4.6.  See bbs.archlinux.org/viewtopic.php

After some experiments, this did work for me:

$ sudo inputattach --daemon -w8001 /dev/ttyS4

...what I don't understand, because my ELAN Touchscreen is definitely not on serial port so there should not be reason to use inputattach at all.

The problem with this is that inputattach process gets D status (uninterruptible sleep) so it makes the suspend/resume to take about 20 seconds (which is some timeout) and sometimes it does not work at all. Since you cannot kill this proccess, it is quite sad and it might imply any other issues eventually.

So this is not solution but might be some indice to find out what the real problem is. I also see this:

$ dmesg | grep -ie elan
[ 7.637031] usb 1-4: Manufacturer: ELAN
[ 10.101754] input: ELAN Touchscreen as /devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4:1.0/0003:04F3:20D0.0001/input/input12
[ 10.101852] hid-multitouch 0003:04F3:20D0.0001: input,hiddev0,hidraw0: USB HID v1.10 Device [ELAN Touchscreen] on usb-0000:00:14.0-4/input0
[ 698.403796] input: ELAN Touchscreen as /devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4:1.0/0003:04F3:20D0.0001/input/input18
[ 698.404299] hid-multitouch 0003:04F3:20D0.0001: input,hiddev0,hidraw0: USB HID v1.10 Device [ELAN Touchscreen] on usb-0000:00:14.0-4/input0

...I wonder why it is input18 instead of input12 after first resume (might change after another suspend/resume?!). So maybe, there is something waiting for input12 but it has changed to input18 while something expects it on 12? I don't know.

That's just my two cents, and I am hefeby joining the question how to fix this completely and properly :)

same problem here  with xps 13 DE 9350 running ubuntu 16.04 kernel 4.4 (or latest kernel 4.7).

I have found a weird workaround:

close the lid just to enter suspend state, but then reopen it quickly, so that it stays in suspend state even when the lid is open. Then press power button to wake it up. Then the touchscreen works again ! 

Yes, I confirm that works for me too.  With the 4.4 kernel, 16.04.

Wonderful! I did it very quickly so that I didn't have to press the power button and it just locked screen and started to work again. Given this, we may be able to do some kernel debugging now...

Yeah, the quick lid close works for me as well. Weird.

Any luck debugging this further?

Can also confirm same workaround works. Don't even have to close the lid fully, just move it down a bit then up - the display doesn't even go dark - and touch is working again.

This seems to still be an issue with the latest 1.4.4 firmware. It's not that big of a deal to me given the workaround of closing it and then opening it again right away seems to fix it.

Did you solve the problem?

Apart from this minor problem - for which there is an easy fix, I think its a good laptop, and well supported...

at least compared with other laptops I've had...

Same problem here.  Close lid briefly and then power button also works for me, but clearly that's not a long term solution.

Ubuntu 16.04 LTS - latest updates.

Wondering if I made a mistake buying this.  16.04 is still not yet officially supported...

I get this on the official Dell ubuntu 14.04 that came with my laptop. It has only been a problem since I accepted the ubuntu "hardware enablement" stack thing recently.

This is now fixed in the kernel. I reached out to the developer who fixed it and he was able to help me make a more reasonable workaround while we wait for that code to be released.

gist.github.com/.../16d07928e3d5d60960aa91dc67f0ad32