USB devices not detected when running on battery

[tomchiverton]

If my laptop is running on battery, and I connect a USB device, nothing happens. If I plug the laptop into the mains, then plug the device in, I get the KDE pop up notice asking me what to do.

Anyone got any ideas why this could be ?

I've just noticed this, and it certainly worked a few weeks ago when I last tried, so I wonder if an update has changed something...

[dibl]

Re: USB devices not detected when running on battery

What kind of USB device? If it is a disk drive that gets power from the USB connector, then probably it's a "feature" to save the battery.

[tomchiverton]

Re: USB devices not detected when running on battery

No, it's my phone, and it used to work fine.

It also occurs with my sat. nav., ditto, so it's not the external devices fault.

[dibl]

Re: USB devices not detected when running on battery

Is there any chance the battery is not holding a good charge any more? It sounds like a power sensor is cutting off power to the USB connector when faced with a current draw, unless the system is plugged into the mains.

[tomchiverton]

Re: USB devices not detected when running on battery

Good guess, but both the KDE battery gauge and lshal indicate all is well:

root@wopr:~# lshal|grep battery
udi = '/org/freedesktop/Hal/devices/computer_power_supply_battery_BAT0'
 battery.charge_level.current = 64357 (0xfb65) (int)
 battery.charge_level.design = 73260 (0x11e2c) (int)
 battery.charge_level.last_full = 69086 (0x10dde) (int)
 battery.charge_level.percentage = 93 (0x5d) (int)
 battery.charge_level.rate = 16872 (0x41e8) (int)
 battery.is_rechargeable = true (bool)
 battery.model = 'DELL HP' (string)
 battery.present = true (bool)
 battery.rechargeable.is_charging = false (bool)
 battery.rechargeable.is_discharging = true (bool)
 battery.remaining_time = 13731 (0x35a3) (int)
 battery.reporting.current = 5798 (0x16a6) (int)
 battery.reporting.design = 6600 (0x19c8) (int)
 battery.reporting.last_full = 6224 (0x1850) (int)
 battery.reporting.rate = 1520 (0x5f0) (int)
 battery.reporting.technology = 'Li-ion' (string)
 battery.reporting.unit = 'mAh' (string)
 battery.serial = '1' (string)
 battery.technology = 'lithium-ion' (string)
 battery.type = 'primary' (string)
 battery.vendor = 'SMP' (string)
 battery.voltage.current = 12032 (0x2f00) (int)
 battery.voltage.design = 11100 (0x2b5c) (int)
 battery.voltage.unit = 'mV' (string)

[dibl]

Re: USB devices not detected when running on battery

My guess is something in the "policykit" region of your system has changed -- don't know why it would, or exactly how to fix it. But it should be possible to change the behavior, which is clearly tied to the question of whether the system is on battery or mains.

[tomchiverton]

Re: USB devices not detected when running on battery

Is there a GUI or sensible command line for looking at it's rules ? What about something like pm-utils ? There are a few hints kicking around the internet, but the best fit for my symptoms seems to be on Arch rather than Ubuntu :
https://bbs.archlinux.org/viewtopic.php?id=113611
https://bbs.archlinux.org/viewtopic.php?id=120359

[dibl]

Re: USB devices not detected when running on battery

Yes, those bug reports look exactly like your symptom. Arch uses plain vanilla KDE, as far as I know, so a fix that works for Arch Linux will probably work for Kubuntu as well.

FYI, it is also true for Debian that if you hibernate or "sleep" the computer, then the USB bus has lost track of what was connected in the prior session, and you might have to reboot to get the webcam or other device to work again. I have had that experience in recent weeks. I see that also reported for Arch.

[oshunluvr]

Re: USB devices not detected when running on battery

Any chance your BIOS has a power saving setting that disables some or all of the USB ports when on battery power? One of my Dell's turns off the ethernet port when in battery only mode.

[tomchiverton]

Re: USB devices not detected when running on battery

No chance, it worked until recently, and I don't spend hours playing with the BIOS

[tomchiverton]

Re: USB devices not detected when running on battery

Do you mean "power management" ? There isn't a relevant tickbox in the profiles as far as I can tell.