On Wed, Jul 17, 2019 at 05:31:33PM +0200, Nicolas Saenz Julienne wrote: > The dma physical limit has so far been calculated based on the memory > size and the assumption that dma would be at least able to address the > first 4 GB. This turned out no to be true with the Raspberry Pi 4 > which, on it's main interconnect, can only address the first GB of > memory, even though it might have up to 4 GB. > > With the current miscalculated dma physical limit the contiguous memory > reserve is located in an inaccessible area for most of the board's > devices. > > To solve this we now scan the device tree for the 'dma-ranges' property > on the root or interconnect nodes, which allows us to calculate the > lowest common denominator dma physical limit. If no dma-ranges is > available, we'll default to the old scheme. > > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulie...@suse.de> > --- > arch/arm64/mm/init.c | 61 +++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 57 insertions(+), 4 deletions(-)
I'd rather have this parsing in the core code, returning setting the minimum DMA mask (or range, address etc.) that covers all devices/buses described. -- Catalin
