FreeRTOS + Zynq 7000: nested interrupts do not work

jimbuteau wrote on Wednesday, June 13, 2018:

soc: XC7Z020 with dual cortexA9 (Trenz TE0720)
sdk: 2017.2
os: FreeRTOS 9.0
interrupt driver: scugic_v3_7

My system is running well (single core) with several interrupts but without interrupt nesting (pre-emption). My two highest priority interrupts are running at priority 18 (TTC) and 19 (axidma). I would very much like nested interrupt handling to work so that the timer interrupt could pre-empt the dma interrupt (as well as all the other lower priority interrupts).

In searching for a solution the closest I’ve come is from 2014:

Unfortunately this solution does not work for me and leads to problems.

First of all, the addition of the following line (as instructed):

XScuGic_CPUWriteReg(InstancePtr, XSCUGIC_BIN_PT_OFFSET, 0x03);

results in an ASSERT fail at:


Secondly, if I skip the XSCUGIC_BIN_PT_OFFSET write and just insert the two functions, Xil_EnableNestInterrupts() and Xil_DisableNestInterrupts() in my interrupt handler(s) as instructed my program crashes at taskEXIT_CRITICAL() in xTaskResumeAll() after the very first interrupt handler call.

Note the the scugic driver html doc contains the comment: Nested interrupts are not supported by this driver

Am I going about this the right way? I would VERY MUCH like to have this feature working and would greatly appreciate any help at all.

rtel wrote on Wednesday, June 13, 2018:

Sorry for brief reply at this time - but FreeRTOS manages the interrupts
so I shouldn’t get too distracted by Xilinx docs unless they are
specific to their FreeRTOS BSP. The Zynq demo in the FreeRTOS kernel
download includes interrupt nesting tests so perhaps you could use those
as a reference for how to set this up. Look at the “IntQTimer” files
which configures different timers at different interrupt priorities.