[Gta04-owner] UARTs modem status interrupt

Dr. H. Nikolaus Schaller hns at goldelico.com
Tue Dec 18 21:48:09 CET 2012

Hi George,

Am 18.12.2012 um 14:52 schrieb George Refseth:

> Hi
> I am making a QNX Neutrino bsp for GTA04, and am getting the OS to run, I am mounting the SD card, but have problems with the UARTs,
> I can't seem to clear the modem status interrupts. Even when they are disabled, they keep hitting me. I am booting with X-loader and uboot, and I am not changing
> any of the PADCONF registers, and a readback verifies that.
> Anyone struggled with such issues when originally bringing up the gta04?

Well, we had a working Linux image for the Beagle Board that did need
only small extensions.

How are you handling these interrrupts?

As far as I understand the OMAP3 SoC, there is an interrupt controller
that can mask and prioritize 96 interrupt sources and generate IRQ or FIQ
on the CPU. The mapping of the 96 interrupts to SoC building blocks is

But the interrupts are level sensitive, i.e. they must be cleared in the peripheral.
And, the peripheral block may have an additional status register telling
what the reason for asserting the interrupt was.

So I think you must find out which interrupt it was and then go to the
device register and clear the interrupt status.

For the UARTs it should be the IIR_REG to find out which interrupt
did occur. But what I did not find while glimpsing into the manual is how to
clear an interrupt. Maybe it is automatically cleared by an appropriate action
(e.g. reading a received character or disabling the interrupt if no longer

> best regards,
> George Refseth

I hope this helps a tiny bit.


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