Hi all, Various Marvell chips (ARM SoCs, MIPS/PPC northbridges, standalone PCI/PCIe SATA/etc. controllers) use an on-chip bus called MBUS. An MBUS bus address consists of not only a 32/64-bit address, but also of a target/attribute ID, which identify which of the connected MBUS peripherals the access is intended for. I.e., transactions are routed explicitly, rather than implicitly based on their address. Peripherals map DMA addresses (as handed to them via e.g. TX/RX descriptors) to MBUS bus addresses via a set of programmable per-peripheral address map windows. In the typical ARM/PPC case, each DMA-capable MBUS peripheral is programmed such that its entire DMA address range points to the on-chip DRAM controller. (But if you wanted, you could also map a peripheral's entire DMA address range to e.g. the PCI MEM address range of some on-chip PCI/PCIe controller.) For things like PCIe SATA controllers, you don't need to worry about setting these address windows, but on most of the ARM/PPC/MIPS stuff, the mapping windows don't contain valid values after reset, and the programming has to be done by the bootloader or the kernel. While the MBUS address map registers are an integral part of each peripheral's own register set, these MBUS address map windows are currently programmed directly by platform code, leading to such gems as arch/arm/mach-orion/addr-map.c and arch/powerpc/platforms/chrp/pegasos_eth.c. This patch set is an initial attempt at moving programming of the MBUS register windows for the set of MBUS peripherals that we currently have in-tree drivers for from platform code into drivers. With these patches, info about DRAM target/attribute IDs is prepared by the platform code as usual, but then passed into platform drivers via platform device data, instead of programming that data into the peripherals directly. This avoids duplicating the window programming code across each platform that wants to use these peripherals, and avoids exposing internal peripheral register set details outside of their drivers. Comments appreciated. thanks, Lennert -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
