The ARC HS processor provides an IOC port (I/O coherency bus interface) that allows external devices such as DMA devices to access memory through the cache hierarchy, providing coherency between I/O transactions and the complete memory hierarchy. Some recent SoC with ARC HS (like HSDK) allow to select bus port (IOC or non-IOC port) for connecting DMA devices in runtime. With this patch we can use both HW-coherent and regular DMA peripherals simultaneously. NOTE: This patch series was stress tested on HSDK with iperf3 (ethernet) and bonie++ (usb and sdio) in three configurations: * IOC enabled globaly * IOC disabled globaly * IOC enabled partially (USB & SDIO are connected via IOC AXI port, ethernet is connected to DDR AXI port (non-IOC port) NOTE: If you want to test some device without IOC it is not enough to remove "dma-coherent" property from dts. You had to remap this device to regular DDR AXI port intead of IOC AXI port. You also need to apply 3 following patches firstly: https://www.mail-archive.com/linux-snps-arc@xxxxxxxxxxxxxxxxxxx/msg03865.html https://www.mail-archive.com/linux-snps-arc@xxxxxxxxxxxxxxxxxxx/msg03889.html https://www.mail-archive.com/linux-snps-arc@xxxxxxxxxxxxxxxxxxx/msg03887.html NOTE: We don't touch any aperture configuration in this patch series. So we don't switch any devices between IOC and non-IOC AXI ports on any board. It can be done later if it is required. Changes v1->v2 (Thanks to Christoph): * Don't select DMA_DIRECT_OPS explicitly as it is already selected by DMA_NONCOHERENT_OPS * Remove check for HIGHMEM pages from arch_dma_{alloc, free} Eugeniy Paltsev (4): ARC: DTS: mark DMA devices connected through IOC port as dma-coherent ARC: allow to use IOC and non-IOC DMA devices simultaneously ARC: IOC: panic if both IOC and ZONE_HIGHMEM enabled ARC: don't check for HIGHMEM pages in arch_dma_alloc arch/arc/boot/dts/axc003.dtsi | 26 ++++++++++++++++ arch/arc/boot/dts/axc003_idu.dtsi | 26 ++++++++++++++++ arch/arc/boot/dts/hsdk.dts | 4 +++ arch/arc/include/asm/dma-mapping.h | 13 ++++++++ arch/arc/mm/cache.c | 30 +++++++++--------- arch/arc/mm/dma.c | 62 +++++++++++++++++++------------------- 6 files changed, 115 insertions(+), 46 deletions(-) create mode 100644 arch/arc/include/asm/dma-mapping.h -- 2.14.4
