I'm a few months late, but if anyone is interested I got it working: https://github.com/Pikrass/pios (see sd.c and dma.c)
I figured the bits for the DMA block thanks to the Linux source.

I pass the destination buffer as the actual (non-cached) physical address.

You need to declare the mailbox addresses (and, in fact, all peripheral addresses) as volatile, so that the optimizer don't turn this: while(*mailboxStatus & MAILBOX_FULL); into this: unsigned int val = *mailboxStatus & MAILBOX_FULL; while(val); The volatile keyword tells the compiler that that addr...

Hi! I'm trying to fetch the available RAM for the ARM. I have a Model B Pi. However, no matter what I put in config.txt, it always appear I have 128 MB of memory (starting from 0, size 0x8000000). I tried getting the result with both ATAGS and the mailbox property interface, but I get the same thing...