DART nodes for dcp and disp0 have pre-allocated L1 and L2 tables which
are annotated in the ADT. The pre-allocated memory is specified in
"pt-region-${DEVICE}". The first page is used as L1 table and the
following pages are used as L2 tables. The number of valid L2 tables is
specified in "l2-tt-${DEVICE}". The first entry identifies the region
and the second entry is the number of valid L2 tables.
iboot (macOS 12.3) inits just 2 L2 tables. Larger framebuffers require
more. By using the pre-allocated page tables we do not have worry about
keeping the memory mapped after m1n1 executes the next target.
Signed-off-by: Janne Grunau <j@jannau.net>
This allows payloads to use DMA for anything that's not PCIe
even without a DART driver. It also restores the DART registers
the state the were left by iBoot.
Signed-off-by: Sven Peter <sven@svenpeter.dev>
