Lynx Point USB - large amount of interrupts (300k / second)

[Adrian Chadd]

hi,

I have a haswell desktop box at home:

CPU: Intel(R) Core(TM) i5-4460  CPU @ 3.20GHz (3192.67-MHz K8-class CPU)

With lynx point USB:

adrian at test-2:~ % dmesg | grep ehci
ehci0: <Intel Lynx Point USB 2.0 controller USB-B> mem
0xf7f1c000-0xf7f1c3ff irq 16 at device 26.0 on pci0
usbus1 on ehci0
ehci1: <Intel Lynx Point USB 2.0 controller USB-A> mem
0xf7f1b000-0xf7f1b3ff irq 23 at device 29.0 on pci0
usbus2 on ehci1


ehci0 at pci0:0:26:0:    class=0x0c0320 card=0x367d17aa chip=0x8c2d8086
rev=0x05 hdr=0x00
    vendor     = 'Intel Corporation'
    device     = 'Lynx Point USB Enhanced Host Controller'
    class      = serial bus
    subclass   = USB

ehci1 at pci0:0:29:0:      class=0x0c0320 card=0x367d17aa chip=0x8c268086
rev=0x05 hdr=0x00
    vendor     = 'Intel Corporation'
    device     = 'Lynx Point USB Enhanced Host Controller'
    class      = serial bus
    subclass   = USB


and:

xhci0: <Intel Lynx Point USB 3.0 controller> mem 0xf7f00000-0xf7f0ffff
irq 16 at device 20.0 on pci0
xhci0: 32 byte context size.
xhci0: Port routing mask set to 0xffffffff
usbus0 on xhci0

xhci0 at pci0:0:20:0:      class=0x0c0330 card=0x367d17aa chip=0x8c318086
rev=0x05 hdr=0x00
    vendor     = 'Intel Corporation'
    device     = 'Lynx Point USB xHCI Host Controller'
    class      = serial bus
    subclass   = USB

.. now, whta I'm seeing is this:

irq16: ehci0                 21441217509      25285
stray irq16                            0          0

... systat -vmstat 1 shows the interrupt rate to be ridiculous though,
like 230,000 interrupts a second.

Proc:                                                            Interrupts
  r   p   d   s   w   Csw  Trp  Sys  Int  Sof  Flt        ioflt  256k total
             45   6  510k   11  245 255k   16    3        cow    255k ehci0 16
                                                        1 zfod        ehci1 23

.. so, what gives? :) Has anyone else seen this?



-adrian