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Honored Contributor I
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How to make a Nios II IRQ assignment to the Altera JTAG UART

Hi all, 

 

I'm currently developing a system that utilizes a Nios II to boot linux (kernel 3.10.31). This system contains several components as well as a JTAG UART. When creating the system in Qsys (v14.0), irq 0 (zero) is currently assigned to the the JTAG UART component. However, as the kernel boots, the following message is reported: 

 

ttyj0 at mmio 0x1001840 (irq = 2) is a altera jtag uart. 

 

 

the memory mapped address for this jtag uart is correct (0x1001840) but it's not clear to me why irq 2 is assigned to this jtag uart when i specifically assigned it to irq 0 in qsys. 

does anyone know where the interrupt assignment for the jtag uart is made for a linux kernel? is it hard coded somewhere to irq 2? i didn't see any options for make this assignment in the kernel makeconfig and there doesn't appear to be any interrupt# define listed in the <boardname>_fpga.h configuration file that is generated from the sopc2dts utility by processing the qsys .sopcinfo file. 

 

using the "cat /proc/interrupts" command doesn't provide any useful information other than to tell me that ttyj0 is assigned to the nios interrupt controller. 

 

is this assignment made directly in the jtag uart driver code for the kernel? 

 

any feedback would be appreciated. 

 

- brad
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