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I/O Coherence Port (IOCP) provides an AXI interface for connecting external non-caching masters, such as DMA controllers. The accesses from IOCP are coherent with D-Caches and L2 Cache. IOCP is a specification option and is disabled on the Renesas RZ/Five SoC due to this reason IP blocks using DMA will fail. The 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. Below are the memory attributes supported: * Device, Non-bufferable * Device, bufferable * Memory, Non-cacheable, Non-bufferable * Memory, Non-cacheable, Bufferable * Memory, Write-back, No-allocate * Memory, Write-back, Read-allocate * Memory, Write-back, Write-allocate * Memory, Write-back, Read and Write-allocate More info about PMA (section 10.3): Link: http://www.andestech.com/wp-content/uploads/AX45MP-1C-Rev.-5.0.0-Datasheet.pdf As a workaround for SoCs with IOCP disabled CMO needs to be handled by software. Firstly OpenSBI configures the memory region as "Memory, Non-cacheable, Bufferable" and passes this region as a global shared dma pool as a DT node. With DMA_GLOBAL_POOL enabled all DMA allocations happen from this region and synchronization callbacks are implemented to synchronize when doing DMA transactions. Example PMA region passes as a DT node from OpenSBI: reserved-memory { #address-cells = <2>; #size-cells = <2>; ranges; pma_resv0@58000000 { compatible = "shared-dma-pool"; reg = <0x0 0x58000000 0x0 0x08000000>; no-map; linux,dma-default; }; }; Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> Reviewed-by: Conor Dooley <conor.dooley@microchip.com> Tested-by: Conor Dooley <conor.dooley@microchip.com> # tyre-kicking on a d1 Link: https://lore.kernel.org/r/20230818135723.80612-6-prabhakar.mahadev-lad.rj@bp.renesas.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> |
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| char | ||
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