On 18 May 2012 01:02, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote: > > Now, the DMA node for an on-SoC DMAC would be in soc.dtsi. Typically, > the DMAC is connected to many on-SoC devices, and hence soc.dtsi would > need to specify the routing information for all those devices to avoid > duplicating it in every board.dts. Now, if you have some DMA requests > that go off-SoC, the board.dts file might want to add to the routing > table to indicate what clients connect to those DMA requests. However, > there's no way in the device tree compiler right now to add to a > property; you can only completely replace it. That would entail > duplicating the entire routing information from soc.dtsi into each > board.dts that wanted to add to it - a bad situation. Splitting the > routing information into chunks in the client nodes avoids this issue > entirely. > As already noted by Russell, the dma setup is different than irq or gpio which deliberately lend to off-SoC attachments. Without fpga'ing, I find it hard to imagine request-signals going off-SoC. I only see the issue of different boards sporting a different sub-sets of clients i.e, a map entry may or may exist for a board but it would be same for two boards that have it. Maybe we could somehow separate out the chan-map and private-data into board.dts ? Even if it has to stay in soc.dts, we still have the benefit of having dmac agnostic client nodes. cheers! -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
