Librem 13 v4 screen blanking issue

Hardware
1

Hi there,

I have a topic open regarding lack of 4K output here:

However there is a linked issue to track this problem:
https://tracker.pureos.net/T298

In this issue a user reports that their external display keeps “flickering” or “turning off”, i am opening this topic as this is something i am also experiencing.

At random intervals when an external monitor is connected, the screen will just turn off for a few seconds and then come back, this never happens with the actual laptop display itself.

Many thanks,

adam

3 Likes
2

I am one of the users in question from the linked issue. Nothing new on my end, other than that it is an odd one where the amount of blanking is very much dependent on the display resolution and I think also somewhat on the CPU load. I should be able to give some more feedback in a few weeks when I can try out a range of different monitors. With my current setup this is not that big of a problem as the blanking with 2560x1440@30Hz is perhaps once an hour or so.

1 Like
3

Hi,

Yes i think you are correct, whenever the fan spins up on my laptop and i see the CPU go above 3Ghz, the display will blank out for a second.

[17628.952878] wlp1s0: Limiting TX power to 23 (23 - 0) dBm as advertised by e6:cb:ac:50:b7:44
[17751.251231] CPU1: Core temperature above threshold, cpu clock throttled (total events = 3440)
[17751.251232] CPU0: Core temperature above threshold, cpu clock throttled (total events = 3440)
[17751.251234] CPU3: Package temperature above threshold, cpu clock throttled (total events = 4968)
[17751.251234] CPU2: Package temperature above threshold, cpu clock throttled (total events = 4968)
[17751.251236] CPU0: Package temperature above threshold, cpu clock throttled (total events = 4164)
[17751.251238] CPU1: Package temperature above threshold, cpu clock throttled (total events = 4164)
[17751.252223] CPU1: Core temperature/speed normal
[17751.252223] CPU0: Core temperature/speed normal
[17751.252224] CPU3: Package temperature/speed normal
[17751.252225] CPU2: Package temperature/speed normal
[17751.252225] CPU0: Package temperature/speed normal
[17751.252226] CPU1: Package temperature/speed normal

This is what dmesg shows, it seems to be doing some power management?

Cheers,

Adam

4

Yes, there is some correlation with the CPU clock, but it is not 100% consistent, at least not for me. What you are observing in dmesg is that the kernel (I do not think it is the intel_pstate driver, but do correct me if I am wrong) detects that the CPU is going hot and then pulls the breaks. For a while I had hard limits in place on the CPU clock to debug a different issue, but I can not remember if that eliminated the blanking entirely. Still, worth a try, I do struggle to get the intel_pstate driver to behave though so do fill me in if you manage to force it to stay below a certain clock, all of my successes were with the generic ACPI driver.

Edit: Completed post, apparently the web interface has some post shortcut I was unaware of.

1 Like
5

I recently installed some monitoring software so that I could revisit blanking after the fact, sadly I am coming up with nothing conclusive. As we have discussed earlier, there is some sort of correlation with the amount of processing going up, it blinks, then returns to normal within a second or two. I looked into CPU clock, disk usage, temperature, etc. at the time of observing the phenomena and there was nothing there as far as I could tell. Yes, the temperature kicks up, yes, the CPU clock goes high, yes, there is throttling, but these things also occur at times when there is no blinking, as well as there being no blinking at times when both the temperature and CPU clock stays high for a significant duration of time.

@adds68 Are you running vanilla PureOS? Wayland or Xorg? Curious since my bet is either driver or something deeper in the hardware that I lack the expertise regarding.

6

I was wondering if anybody has found a solution to the monitor turning off randomly. I just started connecting my Librem 13v4 with updated amber PureOS to an old external monitor. Adapter and cables work on a raspberry pi just fine, however, on my Librem the monitor turns off fairly regulary. It seems to be correlated to the CPU load maybe, as other’s have described already. Trying out this advice:
https://tracker.pureos.net/w/troubleshooting/screen_flickering/
Does not seem to fix anything. Are there any updates on this?
I’m using an old Acer monitor with 1920x1080, connected via HDMI to VGA, so nothing fancy whatsoever.

7

This just occurred to me as I am also experiencing this issue. My PS4 Pro did the same thing for a long while until I started using a higher quality HDMI cable. I will try the PS4’s cable and see if the problem goes away.

8

That would be interesting. I have in the meantime found that using an HDMI - HDMI cable really makes the issue better but it does not completely go away. However, it lets me work and I don’t care too much. Would be interesting to see if the higher quality HDMI cable does the trick. This one literally says amazon basics on it, so I guess it’s a basic cable :wink:

One thing that always makes my monitor flicker is using a HDMI to DVI or HDMI to VGA cable.

Either way, with the HDMI cable it still seems to mainly happen when the CPU is loaded and it only happens when the computer is plugged into the power. Does the house have dirty grounds: I’m fairly certain it does, no proof, but it’s hard enough to find a ground at all here. Does it happen with my work OSX and HP laptops that are now all here, nope. Still love my Librem!

1 Like
9

@pfm What is the coreboot version on your laptop?

10

@mladen I’m on a Librem 13 v4 with PureBoot-beta-11
I guess that is the most recent one from looking at the coreboot_util script.

1 Like
11

I used the high end cable that I use with my PS4 and that didn’t solve the problem.

12

Where do I check my coreboot version?

13

You can simply run the following command in the terminal:

sudo dmidecode -s bios-version

I just took that directly from the coreboot_util.sh shell script that Purism provides for updated your coreboot / pureboot. The current version is checked in that script in Line 165.

Line 58, 59 show the current version of coreboot with and without heads (assuming I read it right):

COREBOOT_SEABIOS_VERSION="4.11-Purism-1" 
COREBOOT_HEADS_VERSION="PureBoot-beta-11"
14

Are there any news on this issue? I have a librem 13 and try to use a Dell monitor, but the flickering is so bad I cant use it. I have tried https://tracker.pureos.net/w/troubleshooting/screen_flickering/ and also the newest hdmi cable, but it didnt help.
If you just tell me which monitor works with librem products I would also be happy.
Thanks!