Hi all, this series attempts to address some issues we found while bringing up the new Raspberry Pi 4 in arm64 and it's intended to serve as a follow up of this discussion: https://lkml.org/lkml/2019/7/17/476 The new Raspberry Pi 4 has up to 4GB of memory but most peripherals can only address the first GB: their DMA address range is 0xc0000000-0xfc000000 which is aliased to the first GB of physical memory 0x00000000-0x3c000000. Note that only some peripherals have these limitations: the ARM cores, PCIe, V3D, GENET, and 40-bit DMA channels have a wider view of the address space. Part of this is solved in arm32 by setting up the machine specific '.dma_zone_size = SZ_1G', which takes care of the allocating the coherent memory area at the right spot. Yet no buffer bouncing (needed for dma streaming) is available at the moment, but that's a story for another series. Unfortunately there is no such thing as '.dma_zone_size' in arm64 also only ZONE_DMA32 is created which is interpreted by dma-direct and the arm64 code as if all peripherals where be able to address the first 4GB of memory. In the light of this, the series implements the following changes: - Add code that parses the device-tree in oder to find the SoC's common DMA area. - Create a ZONE_DMA whenever that area is needed and add the rest of the lower 4 GB of memory to ZONE_DMA32*. - Create the CMA area in a place suitable for all peripherals. - Inform dma-direct of the new runtime calculated min_mask*. That's all. Regards, Nicolas * These solutions where already discussed on the previous RFC (see link above). --- Nicolas Saenz Julienne (8): arm64: mm: use arm64_dma_phys_limit instead of calling max_zone_dma_phys() arm64: rename variables used to calculate ZONE_DMA32's size of/fdt: add function to get the SoC wide DMA addressable memory size arm64: re-introduce max_zone_dma_phys() arm64: use ZONE_DMA on DMA addressing limited devices dma-direct: turn ARCH_ZONE_DMA_BITS into a variable arm64: update arch_zone_dma_bits to fine tune dma-direct min mask mm: comment arm64's usage of 'enum zone_type' arch/arm64/Kconfig | 4 ++ arch/arm64/mm/init.c | 78 ++++++++++++++++++++++++++------- arch/powerpc/include/asm/page.h | 9 ---- arch/powerpc/mm/mem.c | 14 +++++- arch/s390/include/asm/page.h | 2 - arch/s390/mm/init.c | 1 + drivers/of/fdt.c | 72 ++++++++++++++++++++++++++++++ include/linux/dma-direct.h | 2 + include/linux/mmzone.h | 21 ++++----- include/linux/of_fdt.h | 2 + kernel/dma/direct.c | 8 ++-- 11 files changed, 168 insertions(+), 45 deletions(-) -- 2.22.0
