• Thomas Gleixner's avatar
    genirq: reenable a nobody cared disabled irq when a new driver arrives · 1adb0850
    Thomas Gleixner authored
    Uwe Kleine-Koenig has some strange hardware where one of the shared
    interrupts can be asserted during boot before the appropriate driver
    loads. Requesting the shared irq line from another driver result in a
    spurious interrupt storm which finally disables the interrupt line.
    
    I have seen similar behaviour on resume before (the hardware does not
    work anymore so I can not verify).
    
    Change the spurious disable logic to increment the disable depth and
    mark the interrupt with an extra flag which allows us to reenable the
    interrupt when a new driver arrives which requests the same irq
    line. In the worst case this will disable the irq again via the
    spurious trap, but there is a decent chance that the new driver is the
    one which can handle the already asserted interrupt and makes the box
    usable again.
    
    Eric Biederman said further: This case also happens on a regular basis
    in kdump kernels where we deliberately don't shutdown the hardware
    before starting the new kernel.  This patch should reduce the need for
    using irqpoll in that situation by a small amount.
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Tested-and-Acked-by: default avatarUwe Kleine-König <Uwe.Kleine-Koenig@digi.com>
    1adb0850
spurious.c 6.13 KB