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Last time I have strange bugs with my laptop keyboard.

Some of the keys stop working time to time. More often it is shift keys, but some times it also a, s, d, k, l, ;, and others. But they doesn't stop working completely. Instead they 'lost' about 70% of pushes. If I'll hold key pressed - they will start to respond after few seconds.

I've tried external USB keyboard, it works a bit better, but almost the same. At some time shift keys just stop working, and I have to press it multiple times to get it ot work.

Reboot and plug/unplug keyboard doesn't help.

What it could be, and where to start fixing it?

System: Debian GNU/Linux 8 (jessie)

Notebook: Dell Inspiron 15-5547

UPD

$ uname -a

Linux mybox 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt25-2 (2016-04-08) x86_64 GNU/Linux

$ cat /var/logs/kern.log

Apr 25 10:56:07 aschukarev kernel: [  541.163523] usb 1-1: new low-speed USB device number 3 using xhci_hcd
Apr 25 10:56:07 aschukarev kernel: [  541.352793] usb 1-1: New USB device found, idVendor=1c4f, idProduct=0002
Apr 25 10:56:07 aschukarev kernel: [  541.352800] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
Apr 25 10:56:07 aschukarev kernel: [  541.352804] usb 1-1: Product: USB Keyboard
Apr 25 10:56:07 aschukarev kernel: [  541.352807] usb 1-1: Manufacturer: SIGMACHIP
Apr 25 10:56:07 aschukarev kernel: [  541.353035] usb 1-1: ep 0x81 - rounding interval to 64 microframes, ep desc says 80 microframes
Apr 25 10:56:07 aschukarev kernel: [  541.353042] usb 1-1: ep 0x82 - rounding interval to 64 microframes, ep desc says 80 microframes
Apr 25 10:56:07 aschukarev kernel: [  541.356152] input: SIGMACHIP USB Keyboard as /devices/pci0000:00/0000:00:14.0/usb1/1-1/1-1:1.0/0003:1C4F:0002.0004/input/input19
Apr 25 10:56:07 aschukarev kernel: [  541.356376] hid-generic 0003:1C4F:0002.0004: input,hidraw3: USB HID v1.10 Keyboard [SIGMACHIP USB Keyboard] on usb-0000:00:14.0-1/input0
Apr 25 10:56:07 aschukarev kernel: [  541.359067] input: SIGMACHIP USB Keyboard as /devices/pci0000:00/0000:00:14.0/usb1/1-1/1-1:1.1/0003:1C4F:0002.0005/input/input20
Apr 25 10:56:07 aschukarev kernel: [  541.359323] hid-generic 0003:1C4F:0002.0005: input,hidraw4: USB HID v1.10 Device [SIGMACHIP USB Keyboard] on usb-0000:00:14.0-1/input1
Apr 25 11:04:01 aschukarev kernel: [ 1015.796519] cfg80211: Calling CRDA to update world regulatory domain
Apr 25 11:04:01 aschukarev kernel: [ 1015.799421] cfg80211: World regulatory domain updated:
Apr 25 11:04:01 aschukarev kernel: [ 1015.799425] cfg80211:  DFS Master region: unset
Apr 25 11:04:01 aschukarev kernel: [ 1015.799426] cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp), (dfs_cac_time)
Apr 25 11:04:01 aschukarev kernel: [ 1015.799429] cfg80211:   (2402000 KHz - 2472000 KHz @ 40000 KHz), (N/A, 2000 mBm), (N/A)
Apr 25 11:04:01 aschukarev kernel: [ 1015.799431] cfg80211:   (2457000 KHz - 2482000 KHz @ 40000 KHz), (N/A, 2000 mBm), (N/A)
Apr 25 11:04:01 aschukarev kernel: [ 1015.799433] cfg80211:   (2474000 KHz - 2494000 KHz @ 20000 KHz), (N/A, 2000 mBm), (N/A)
Apr 25 11:04:01 aschukarev kernel: [ 1015.799435] cfg80211:   (5170000 KHz - 5250000 KHz @ 80000 KHz, 160000 KHz AUTO), (N/A, 2000 mBm), (N/A)
Apr 25 11:04:01 aschukarev kernel: [ 1015.799438] cfg80211:   (5250000 KHz - 5330000 KHz @ 80000 KHz, 160000 KHz AUTO), (N/A, 2000 mBm), (0 s)
Apr 25 11:04:01 aschukarev kernel: [ 1015.799440] cfg80211:   (5490000 KHz - 5730000 KHz @ 160000 KHz), (N/A, 2000 mBm), (0 s)
Apr 25 11:04:01 aschukarev kernel: [ 1015.799441] cfg80211:   (5735000 KHz - 5835000 KHz @ 80000 KHz), (N/A, 2000 mBm), (N/A)
Apr 25 11:04:01 aschukarev kernel: [ 1015.799443] cfg80211:   (57240000 KHz - 63720000 KHz @ 2160000 KHz), (N/A, 0 mBm), (N/A)
Apr 25 11:04:07 aschukarev kernel: [ 1021.787723] wlan0: authenticate with 4c:5e:0c:cc:2f:4f
Apr 25 11:04:07 aschukarev kernel: [ 1021.798007] wlan0: send auth to 4c:5e:0c:cc:2f:4f (try 1/3)
Apr 25 11:04:07 aschukarev kernel: [ 1021.902153] wlan0: send auth to 4c:5e:0c:cc:2f:4f (try 2/3)
Apr 25 11:04:07 aschukarev kernel: [ 1022.006224] wlan0: send auth to 4c:5e:0c:cc:2f:4f (try 3/3)
Apr 25 11:04:08 aschukarev kernel: [ 1022.110330] wlan0: authentication with 4c:5e:0c:cc:2f:4f timed out
Apr 25 11:04:09 aschukarev kernel: [ 1023.089460] wlan0: authenticate with 02:0c:42:8d:b3:92
Apr 25 11:04:09 aschukarev kernel: [ 1023.098803] wlan0: direct probe to 02:0c:42:8d:b3:92 (try 1/3)
Apr 25 11:04:09 aschukarev kernel: [ 1023.299023] wlan0: direct probe to 02:0c:42:8d:b3:92 (try 2/3)
Apr 25 11:04:09 aschukarev kernel: [ 1023.503174] wlan0: send auth to 02:0c:42:8d:b3:92 (try 3/3)
Apr 25 11:04:09 aschukarev kernel: [ 1023.615212] wlan0: authentication with 02:0c:42:8d:b3:92 timed out
Apr 25 11:04:10 aschukarev kernel: [ 1024.696674] wlan0: authenticate with 4c:5e:0c:cc:2f:4f
Apr 25 11:04:10 aschukarev kernel: [ 1024.707638] wlan0: send auth to 4c:5e:0c:cc:2f:4f (try 1/3)
Apr 25 11:04:10 aschukarev kernel: [ 1024.709527] wlan0: authenticated
Apr 25 11:04:10 aschukarev kernel: [ 1024.711912] wlan0: associate with 4c:5e:0c:cc:2f:4f (try 1/3)
Apr 25 11:04:10 aschukarev kernel: [ 1024.728029] wlan0: RX AssocResp from 4c:5e:0c:cc:2f:4f (capab=0x431 status=0 aid=3)
Apr 25 11:04:10 aschukarev kernel: [ 1024.728071] wlan0: associated

Messages about USB keyboard at the beginning - i'd plugged in external keyboard, because embedded started to lag.

  • The obvious possibility is hardware problems. Have you tried it with a different operating system? You could try a live CD/DVD, for example. – Faheem Mitha Apr 25 '16 at 8:43
  • What kind of keyboard is that? A flexible one? I would go for intermittent contact problems in the keyboard matrix PCB... – Rui F Ribeiro Apr 25 '16 at 9:57
  • Integrated notebook keyboard is usual integrated keyboard. External is also usual wired USB keyboard with high profile buttons. There is shure no contact problems because of the same troubles with to absolyte diferent hardware keyboards. – AlexLocust Apr 25 '16 at 14:02
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Check the kernel processes wouldn't be on loop check top command and also check your kern.log and log for issue. You can find them on : /var/log/kern.log I guess Kernel won't accept keyboard interrupts sometimes.

| improve this answer | |
  • Thank you for IRQ idea. I've checked log (added in post), also I've updated my system to latest version in repo and installed package irqbalance. But it didn't seems to help :( – AlexLocust Apr 25 '16 at 8:20
  • irqbalance is to distribute interrupt load across CPUs in busy systems; it wont help with IRQ conflicts. – Rui F Ribeiro Apr 25 '16 at 9:59
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There was hardware issue. Other external keyboard works great, and the problem is the same on other OS. Looks like some kind of heating problem. If I'll leave notebook off for few days, bugs gone. If I'll let it work all night - things go worse.

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Could be, that you have hardware or connection issues. I watered my USB-keyboard twice which led to the exact behavior you describe and changed the inner keyboard of my laptop once because a whole column of letters stopped working. My guess is that in the latter case, the flexible cable was broken.

| improve this answer | |

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