Hi All, On the Andes AX45MP core, cache coherency is a specification option so it may not be supported. In this case DMA will fail. To get around with this issue this patch series does the below: Andes AX45MP core has a Programmable Physical Memory Attributes (PMA) block that allows dynamic adjustment of memory attributes in the runtime. It contains a configurable amount of PMA entries implemented as CSR registers to control the attributes of memory locations in interest. PMA regions are passed from the cpu core node which are configured as non-cacheable and non-bufferable with the SBI call. ax45mp: cpu@0 { compatible = "andestech,ax45mp", "riscv"; device_type = "cpu"; .... pma-regions = <0x0 0x00000000 0x0 0x14000000>, <0x0 0x20000000 0x0 0x10000000>, <0x0 0x58000000 0x0 0x08000000>; .... }; We provide callbacks to synchronize specific content between memory and cache. We allocate a global DMA coherent pool (which is marked as non-cached using PMA) so that DMA memory allocations happens from this pool and we implement the below callbacks: - arch_sync_dma_for_device() - arch_sync_dma_for_cpu() - arch_dma_alloc() - arch_dma_free() Below are the configs that are enabled: - DMA_GLOBAL_POOL - ARCH_HAS_SYNC_DMA_FOR_CPU - ARCH_HAS_SYNC_DMA_FOR_DEVICE l2cache: cache-controller@13400000 { compatible = "andestech,ax45mp-cache", "cache"; cache-size = <0x40000>; cache-line-size = <64>; cache-sets = <1024>; cache-unified; reg = <0x0 0x13400000 0x0 0x100000>; }; Due to the above approach custom SBI calls have been implemented. The above implementation is in preparation for adding support for Renesas RZ/Five SoC which uses the AX45MP core. As with the above approach the kernel image might not be generic so that it can be used on other platforms, so sending it as an RFC (without DT binding patches). OpenSBI implementation isn't upstreamed yet, public repo for access is available at [0]. [0] https://github.com/renesas-rz/rz_opensbi/tree/work/OpenSBI-PMA Cheers, Prabhakar Lad Prabhakar (2): riscv: vendors: andes: Add support to configure the PMA regions riscv: vendors: andes: Add support for non-cohernet dma arch/riscv/Kbuild | 2 + arch/riscv/include/asm/sbi.h | 1 + arch/riscv/vendors/Makefile | 3 + arch/riscv/vendors/andes/Makefile | 4 + arch/riscv/vendors/andes/ax45mp.c | 93 ++++++ arch/riscv/vendors/andes/ax45mp_cache.c | 296 ++++++++++++++++++ arch/riscv/vendors/andes/ax45mp_nocache_dma.c | 65 ++++ arch/riscv/vendors/andes/include/proc.h | 9 + arch/riscv/vendors/andes/include/sbi.h | 27 ++ 9 files changed, 500 insertions(+) create mode 100644 arch/riscv/vendors/Makefile create mode 100644 arch/riscv/vendors/andes/Makefile create mode 100644 arch/riscv/vendors/andes/ax45mp.c create mode 100644 arch/riscv/vendors/andes/ax45mp_cache.c create mode 100644 arch/riscv/vendors/andes/ax45mp_nocache_dma.c create mode 100644 arch/riscv/vendors/andes/include/proc.h create mode 100644 arch/riscv/vendors/andes/include/sbi.h -- 2.25.1