After updating the firmware for working with the Raspberry Pi 2 V1.2 (a.k.a. 2B+), the PL011 FIQ is mostly unreliable.
It applies for all models. The issue seems to be with the firmware upgrade to support the Raspberry Pi 2 V1.2 and changing the default UART CLOCK speed.
The good scenario :
I set the UART clock to 3MHz using the Set Clock Rate mailbox tag.
Then set the IBRD/FBRD with the correct values to support 31250 baud.
The bad scenario :
I set the UART clock to 4MHz using the Set Clock Rate mailbox tag.
Then set the IBRD=1/FBRD=0 to support 250000 baud.
=> Mostly it does not work. I get it working by switching off/on the Raspberry Pi multiple times.
I am pretty lost here. What could have been changed in the firmware which makes the 4Mhz setting unreliable?
Many thanks in advance,