I am running a userspace UART driver for UART1, on top of a microkernel. The whole thing is running in secure mode. The UART driver is executed in userspace. The kernel can send logs through the UART alright but my userspace driver is triggering external aborts when trying to do the same. At first I thought there was something wrong with CSL21 in the CSU but it looks like the reset value works for this configuration. I tried to change it to 0xff just to be sure and it didn't change a thing. Am I missing something? Are there any other reasons why a secure user access to a peripheral would fail?