High number of USB interrupts/s on an idle system

Stephen Warren swarren at wwwdotorg.org
Sun Dec 1 13:47:36 EST 2013

On 11/29/2013 04:09 AM, martin sperl wrote:
> Hi!
> I have done the setup of the RPI using Stephens "vanilla" tree (commit:
> d5d9894) and the steps from his blog with regards to uboot, the usb
> power-on hack in uboot, ...
> The thing is that I see high interrupt rates on the board even when the
> system is totally idle.

The USB HW block requires SW to service an interrupt for every USB
frame(?). Whether that should be needed when the HW is idle, I have no
idea. I guess it's quite possible the interrupt needs to stay enabled in
order to e.g. interrupts to be delivered back up the chain.

> I also wonder why I would have 1 MMC interrupt/s, when there is nothing
> happening really on the SD-card...

There are probably many possible reasons; swap, flushing disk buffers,
polling the card to make sure it's still present(?), ... I imagine you'd
need to explicitly instrument the driver to dump commands to tell if you
really want to know.

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