Trying to debug interrupt flood after unbind

[Greg KH]

On Tue, May 31, 2016 at 06:41:24PM +0000, Rob Groner wrote:
> I am trying to load a driver for an Exar serial chip, but that chip is gobbled
> up by the 8250 driver on boot.

Why does the in-kernel driver not support this chip?  Do you have a
pointer to the Exar source anywhere?

> So, I use the “unbind” command in /sys/bus/pci/
> drivers/serial to remove the device from the clutches of 8250.  Based on
> cobbled together google searches, I use the following to unbind it (assuming
> the address in /sys/bus/pci/drivers/serial is 0000:04:00.0.

That's a huge hammer, are you sure that's the best way to do this?  Why
not just add your device to a blacklist in the 8250 driver?

> So, as near as I can tell, when the Exar driver is inserted, an interrupt flood
> occurs, and the Exar driver (the only interrupt handler on that IRQ) does not
> respond to any of them.  I put in some debug code and verified that the Exar
> interrupt handler is called… but the handler just returns with an IRQ_NONE
> value.

Sounds like a bug in the Exar driver, why isn't it handling the
interrupt properly?

thanks,

greg k-h