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Interrupt storm on request_irq() on PCIe devices

Question asked by Andrew Nicolas on Apr 29, 2015
Latest reply on Apr 29, 2015 by Scott Wood

We have a custom hardware design based on the P1022DS board.  We have connected PCIe interfaces 1 and 2 each to their own 2:4 PCIe switch.  One of the PCIe switches has attached to it 2 PCIe devices.  Memory accesses to the 2 PCIe devices work fine, but we are having problems enabling interrupts on the 2 PCIe devices.


When request_irq() is called on each PCIe device, the interrupt storm handler kicks in and disables each IRQ.


The /proc/interrupts output is:



16:          0   OpenPIC    16 Level     fsl-lbc-err, [PCI] PME, [PCI] PME

19:      24170   OpenPIC    19 Level     fsl-lbc

25:     100000   OpenPIC     6 Level     btipci

26:     100000   OpenPIC     7 Level     btipci

42:        383   OpenPIC    42 Level     serial

LOC:       6449   Local timer interrupts

SPU:          0   Spurious interrupts

PMI:          0   Performance monitoring interrupts

MCE:          0   Machine check exceptions


The two entries for "btipci" are the IRQs in question.


Why the discrepancy between the IRQ (25 and 26) and the interrupt type (6 Level and 7 Level)? Is this the reason for the interrupt storm?


BTW, both PCIe devices are using legacy interrupts and have no MSI or MSI-X capabilities.