On Mon, Jun 7, 2021 at 2:51 PM Christoph Hellwig <hch@xxxxxx> wrote: > > On Mon, Jun 07, 2021 at 02:41:14PM +0800, Guo Ren wrote: > > Double/Triple the size of physical memory regions can't be accepted by > > SOC vendors, because it wastes HW resources. > > Some cost-down soc interconnects only have 32bit~34bit width of > > physical address, are you sure you could force them to expand it? (I > > can't) > > > > > or somewhat dynamic. > > How can HW implement with dynamic modifying PMA? What's the granularity? > > I'm just stating the requirements from the Linux DMA perspective. You > also do not need tripple the address space, just double. With double, you only got "strong order + non-cache" for the DMA descriptor. How about write-combine scenario? Even, double physical memory address space also wastes HW resources. -- Best Regards Guo Ren ML: https://lore.kernel.org/linux-csky/
