I finally got UEFI flashed onto the Gigabyte board so now it is SBSA/SBBR compliant [edit: see note at end] and will just work with RHEL. Instructions here: https://lists.centos.org/pipermail/arm-dev/2016-March/001743.html
Here are the boot messages from TianoCore:
TianoCore 1.20.03 UEFI 2.4.0 Jan 26 2016 18:09:04 CPU: APM ARM 64-bit Potenza Rev B0 2400MHz PCP 2400MHz 32 KB ICACHE, 32 KB DCACHE SOC 2000MHz IOBAXI 400MHz AXI 250MHz AHB 200MHz GFC 125MHz Board: X-Gene Mp30ar0 Board Slimpro FW: Ver: 2.4 (build 01.15.01.00 2015/05/22) TPC: disable AVS: support PMD: 970 mV SOC: 950 mV The default boot selection will start in 1 second
Note: A few people have pointed out that the Gigabyte isn’t SBSA compliant because it lacks the right serial port, RTC and WDT. However it still boots RHELSA fine if you add console=ttyS0,115200
.