I have a SoC-FPGA(DE0-nano-soc) which contains an ARM-Cortex-A9 cpu with a Cyclone V FPGA on a single chip. the CPU has access to 1gb of DDR3 memory but the FPGA can also access this memory so they can share data.
Now I have configured linux to only see 900M of the total RAM using the boot parameter
mem=900M. This way I have some RAM left linux doesn't touch that I can use to communicate with the FPGA. I want to write to that part of the RAM using
/dev/mem. I get a permission denied error when I memory map the appropriate address, I am guessing this is because my kernel has
Now I don't really want to unset this since I really only need to write to adresses which linux doesn't use. Is there a way to tell the linux kernel that it is fine to write to that specific part but the normal memory is still of limits?