screen stays blank following power management on idle?

cfr · 2012-07-27 00:45:00

Recently, I've noticed several occasions when I've returned to my laptop after some time to find that the screen is blank (or the display is off? is there a difference?) and that the display does not return on keypress etc.

I've found a number of threads about a superficially similar issue following sleep or attempted sleep but that's not the problem in my case. This has only happened to me (so far) on AC and the laptop is not set to sleep, suspend or hibernate automatically when on AC. Moreover, I don't think I've seen the problem following a resume from sleep etc. In fact, it is sometimes possible to restore the display by putting the machine to sleep and then waking it up. (Either put to sleep using sleep button or closing lid; waking by opening lid and hitting fn key.) All the other reports I've found describe a problem following an attempted sleep/suspend/hibernate.

The other way I can sometimes get the display back is by switching to another tty and then back to X. I'm not sure if it is just that the switch in itself changes something or if the problem is an X-specific one which is overcome by switching from and to X.

I haven't noticed any particular pattern to this. It doesn't happen every time and it is not directly related to how long the laptop is left idling. I might leave it for hours and find it resumes on any key press or I might leave it for half an hour and find I have to mess around to get the display back.

I realise that this is not enough information to suggest a solution (unless somebody recognises exactly the same issue) but I'm hoping somebody can suggest a way to figure out what's going on. Where should I be looking? I can't find anything especially obvious looking in dmesg, for example. (Might not mean much - glaringly clear might be non-obvious to me.) I also haven't found anything suspicious/relevant looking in e.g. ~/.xsession-errors.

I did find one warning from ACPI in dmesg output but googling this has just found a bunch of threads where people explain that it isn't really an error and is probably harmless - may even be importantly protective, in fact, and is just the kernel doing its job. The verdict seems to be: ignore and be happy. Just in case, here's the ACPI warning:

[    8.518350] ACPI: Requesting acpi_cpufreq
[    9.196096] iTCO_vendor_support: vendor-support=0
[    9.196422] thermal LNXTHERM:00: registered as thermal_zone0
[    9.196426] ACPI: Thermal Zone [TZ00] (49 C)
[    9.270402] ACPI: Battery Slot [BAT1] (battery present)
[    9.355245] ACPI Warning: 0x000000000000efa0-0x000000000000efbf SystemIO conflicts with Region \_SB_.PCI0.SBUS.SMBI 1 (20120320/utaddress-251)
[    9.355256] ACPI: If an ACPI driver is available for this device, you should use it instead of the native driver
[    9.359971] mei: module is from the staging directory, the quality is unknown, you have been warned.
[    9.360271] mei 0000:00:16.0: setting latency timer to 64
[    9.360405] mei 0000:00:16.0: irq 42 for MSI/MSI-X

Arch Linux

#1 2012-07-27 00:45:00

screen stays blank following power management on idle?

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