I have a lovely ancient ergonomic keyboard (no name SK - 6000) connected via a DIN->ps/2 adapter to a ps/2->usb adapter to my docking station. After Grub it stops working. It takes either suspending and waking up or replugging it while Linux is running to get it to work. No extra kernel modules get loaded for this. When it works and I restart without power off, it will work immediately.

Even when it does not work, it is visible (lsusb device number varies but output is identical whether working or not):

$ lsusb -v -s 001:006

Bus 001 Device 006: ID 0a81:0205 Chesen Electronics Corp. PS/2 Keyboard+Mouse Adapter
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               1.10
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0         8
  idVendor           0x0a81 Chesen Electronics Corp.
  idProduct          0x0205 PS/2 Keyboard+Mouse Adapter
  bcdDevice            0.10
  iManufacturer           1 CHESEN
  iProduct                2 PS2 to USB Converter
  iSerial                 0 
  bNumConfigurations      1
  Configuration Descriptor:
bLength                 9
bDescriptorType         2
wTotalLength           59
bNumInterfaces          2
bConfigurationValue     1
iConfiguration          2 PS2 to USB Converter
bmAttributes         0xa0
  (Bus Powered)
  Remote Wakeup
MaxPower              100mA
Interface Descriptor:
  bLength                 9
  bDescriptorType         4
  bInterfaceNumber        0
  bAlternateSetting       0
  bNumEndpoints           1
  bInterfaceClass         3 Human Interface Device
  bInterfaceSubClass      1 Boot Interface Subclass
  bInterfaceProtocol      1 Keyboard
  iInterface              0 
    HID Device Descriptor:
      bLength                 9
      bDescriptorType        33
      bcdHID               1.10
      bCountryCode            0 Not supported
      bNumDescriptors         1
      bDescriptorType        34 Report
      wDescriptorLength      64
     Report Descriptors: 
       ** UNAVAILABLE **
  Endpoint Descriptor:
    bLength                 7
    bDescriptorType         5
    bEndpointAddress     0x81  EP 1 IN
    bmAttributes            3
      Transfer Type            Interrupt
      Synch Type               None
      Usage Type               Data
    wMaxPacketSize     0x0008  1x 8 bytes
    bInterval              10
Interface Descriptor:
  bLength                 9
  bDescriptorType         4
  bInterfaceNumber        1
  bAlternateSetting       0
  bNumEndpoints           1
  bInterfaceClass         3 Human Interface Device
  bInterfaceSubClass      1 Boot Interface Subclass
  bInterfaceProtocol      2 Mouse
  iInterface              0 
    HID Device Descriptor:
      bLength                 9
      bDescriptorType        33
      bcdHID               1.10
      bCountryCode            0 Not supported
      bNumDescriptors         1
      bDescriptorType        34 Report
      wDescriptorLength     148
     Report Descriptors: 
       ** UNAVAILABLE **
  Endpoint Descriptor:
    bLength                 7
    bDescriptorType         5
    bEndpointAddress     0x82  EP 2 IN
    bmAttributes            3
      Transfer Type            Interrupt
      Synch Type               None
      Usage Type               Data
    wMaxPacketSize     0x0008  1x 8 bytes
    bInterval              10
Device Status:     0x0000
  (Bus Powered)


$ ll -R /sys/bus/hid/drivers/
/sys/bus/hid/drivers/:
total 0
drwxr-xr-x 2 root root 0 Jul  8  2012 generic-usb/

/sys/bus/hid/drivers/generic-usb:
total 0
lrwxrwxrwx 1 root root    0 Jul  7 23:33 0003:046D:C03D.0003 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.2/1-1.2.2:1.0/0003:046D:C03D.0003/
lrwxrwxrwx 1 root root    0 Jul  7 23:33 0003:0A81:0205.0001 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/
lrwxrwxrwx 1 root root    0 Jul  7 23:33 0003:0A81:0205.0002 -> ../../../../devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.1/0003:0A81:0205.0002/
--w------- 1 root root 4096 Jul  7 23:32 bind
lrwxrwxrwx 1 root root    0 Jul  7 23:33 module -> ../../../../module/usbhid/
--w------- 1 root root 4096 Jul  7 23:32 new_id
--w------- 1 root root 4096 Jul  8  2012 uevent
--w------- 1 root root 4096 Jul  7 23:32 unbind

When replugging, dmesg shows this (which except for the 1st line and different input numbers already came at boot time):

[ 1583.295385] usb 1-1.2.1: new low-speed USB device number 6 using ehci_hcd
[ 1583.446514] input: CHESEN PS2 to USB Converter as /devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/input/input17
[ 1583.446817] generic-usb 0003:0A81:0205.0001: input,hidraw0: USB HID v1.10 Keyboard [CHESEN PS2 to USB Converter] on usb-0000:00:1a.0-1.2.1/input0
[ 1583.454764] input: CHESEN PS2 to USB Converter as /devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.1/input/input18
[ 1583.455534] generic-usb 0003:0A81:0205.0002: input,hidraw1: USB HID v1.10 Mouse [CHESEN PS2 to USB Converter] on usb-0000:00:1a.0-1.2.1/input1
[ 1583.455578] usbcore: registered new interface driver usbhid
[ 1583.455584] usbhid: USB HID core driver

So I tried

$ sudo udevadm test /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/hidraw/hidraw0
run_command: calling: test
adm_test: version 175
This program is for debugging only, it does not run any program,
specified by a RUN key. It may show incorrect results, because
some values may be different, or not available at a simulation run.

parse_file: reading '/lib/udev/rules.d/40-crda.rules' as rules file
parse_file: reading '/lib/udev/rules.d/40-fuse.rules' as rules file
...
parse_file: reading '/lib/udev/rules.d/40-usb-media-players.rules' as rules file
parse_file: reading '/lib/udev/rules.d/40-usb_modeswitch.rules' as rules file
...
parse_file: reading '/lib/udev/rules.d/42-qemu-usb.rules' as rules file
...
parse_file: reading '/lib/udev/rules.d/69-cd-sensors.rules' as rules file
add_rule: IMPORT found builtin 'usb_id', replacing /lib/udev/rules.d/69-cd-sensors.rules:76
...
parse_file: reading '/lib/udev/rules.d/77-mm-usb-device-blacklist.rules' as rules file
...
parse_file: reading '/lib/udev/rules.d/85-usbmuxd.rules' as rules file
...
parse_file: reading '/lib/udev/rules.d/95-upower-hid.rules' as rules file
parse_file: reading '/lib/udev/rules.d/95-upower-wup.rules' as rules file
parse_file: reading '/lib/udev/rules.d/97-bluetooth-hid2hci.rules' as rules file
udev_rules_new: rules use 271500 bytes tokens (22625 * 12 bytes), 44331 bytes buffer
udev_rules_new: temporary index used 76320 bytes (3816 * 20 bytes)
udev_device_new_from_syspath: device 0x7f78a5e4d2d0 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/hidraw/hidraw0'
udev_device_new_from_syspath: device 0x7f78a5e5f820 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/hidraw/hidraw0'
udev_device_read_db: device 0x7f78a5e5f820 filled with db file data
udev_device_new_from_syspath: device 0x7f78a5e60270 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001'
udev_device_new_from_syspath: device 0x7f78a5e609c0 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0'
udev_device_new_from_syspath: device 0x7f78a5e61160 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1'
udev_device_new_from_syspath: device 0x7f78a5e61960 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2'
udev_device_new_from_syspath: device 0x7f78a5e62150 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1/1-1'
udev_device_new_from_syspath: device 0x7f78a5e62940 has devpath '/devices/pci0000:00/0000:00:1a.0/usb1'
udev_device_new_from_syspath: device 0x7f78a5e630f0 has devpath '/devices/pci0000:00/0000:00:1a.0'
udev_device_new_from_syspath: device 0x7f78a5e638a0 has devpath '/devices/pci0000:00'
udev_event_execute_rules: no node name set, will use kernel supplied name 'hidraw0'
udev_node_add: creating device node '/dev/hidraw0', devnum=251:0, mode=0600, uid=0, gid=0
udev_node_mknod: preserve file '/dev/hidraw0', because it has correct dev_t
udev_node_mknod: preserve permissions /dev/hidraw0, 020600, uid=0, gid=0
node_symlink: preserve already existing symlink '/dev/char/251:0' to '../hidraw0'
udev_device_update_db: created empty file '/run/udev/data/c251:0' for '/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/hidraw/hidraw0'
ACTION=add
DEVNAME=/dev/hidraw0
DEVPATH=/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/hidraw/hidraw0
MAJOR=251
MINOR=0
SUBSYSTEM=hidraw
UDEV_LOG=6
USEC_INITIALIZED=969079051

The later lines sound like it's already there. And none of these awakes the keyboard:

$ sudo udevadm trigger --verbose --sysname-match=usb*
/sys/devices/pci0000:00/0000:00:1a.0/usb1
/sys/devices/pci0000:00/0000:00:1a.0/usbmon/usbmon1
/sys/devices/pci0000:00/0000:00:1d.0/usb2
/sys/devices/pci0000:00/0000:00:1d.0/usbmon/usbmon2
/sys/devices/virtual/usbmon/usbmon0

$ sudo udevadm trigger --verbose --sysname-match=hidraw0
/sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/1-1.2.1/1-1.2.1:1.0/0003:0A81:0205.0001/hidraw/hidraw0

$ sudo udevadm trigger

I also tried this to no avail:

# echo -n 0003:0A81:0205.0001 > /sys/bus/hid/drivers/generic-usb/bind
ksh: echo: write to 1 failed [No such device]

# echo -n 0003:0A81:0205.0001 > /sys/bus/hid/drivers/generic-usb/unbind

# echo -n 0003:0A81:0205.0001 > /sys/bus/hid/drivers/generic-usb/bind

# echo usb1 >/sys/bus/usb/drivers/usb/unbind

# echo usb1 >/sys/bus/usb/drivers/usb/bind

What else should I try to get the same result as replugging or suspending, by just issuing a command?