On 6/9/23 15:48, Adam Ford wrote:
I was wondering if anyone has ever attempted to build a 32-bit kernel to run on an RZ/G2 or RCAR3 SoC.
Not me
I have a variant with than 2GB of RAM, and I want to run some experiments to measure RAM utilization and performance to see if it's worth trying to run in 32-bit mode to save a little RAM.
It might be worth looking at arm64 ilp32 too, that retains you the armv8a instructions, i.e. you get the 32bit pointers without the armv7a opcodes downsides.
It looks like U-Boot supports AARCH32, but most of the stuff I can find when searching has people building applications in 32-bit space running on a 64-bit kernel, but I am hoping to try everything in 32-bit mode. I have build the multi_v7 kernel with an ARMv7 compiler, but attempts to boot that kernel cause a crash. I am guessing I need to enable some additional flag somewhere, or somehow tell U-Boot it's a 32-bit kernel.
Maybe look at what RPi does, I think they run 32bit OR 64bit kernel on RPi3 built from the same source and using the same DT .
