Hi Arnd, On Fri, Jan 17, 2014 at 9:43 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Thursday 16 January 2014, Srikanth Thokala wrote: >> @@ -0,0 +1,71 @@ >> +Xilinx AXI VDMA engine, it does transfers between memory and video devices. >> +It can be configured to have one channel or two channels. If configured >> +as two channels, one is to transmit to the video device and another is >> +to receive from the video device. >> + >> +Required properties: >> +- compatible: Should be "xlnx,axi-vdma-1.00.a" >> +- #dma-cells: Should be <1>, see "dmas" property below >> +- reg: Should contain VDMA registers location and length. >> +- interrupts: Should contain per channel VDMA interrupts. >> +- compatible (child node): It should be either "xlnx,axi-vdma-mm2s-channel" or >> + "xlnx,axi-vdma-s2mm-channel". It depends on the hardware design and it >> + can also have both channels. >> +- xlnx,device-id: Should contain device number in each channel. It should be >> + {0,1,2...so on} to the number of VDMA devices configured in hardware. >> +- xlnx,num-fstores: Should be the number of framebuffers as configured in h/w. >> +- xlnx,data-width: Should contain the stream data width, takes {32,64...so on}. >> +- xlnx,flush-fsync: (Optional) Tells whether which channel to Flush on Fsync. >> + It takes following values: >> + {1}, flush both channels >> + {2}, flush mm2s channel >> + {3}, flush s2mm channel >> +- xlnx,include-sg: (Optional) Tells whether configured for Scatter-mode in >> + the hardware. >> +- xlnx,include-dre: (Optional) Tells whether hardware is configured for Data >> + Realignment Engine. >> +- xlnx,genlock-mode: (Optional) Tells whether Genlock synchornisation is >> + enabled/disabled in hardware. > > The documentation doesn't seem to match the example, since you don't mention > the fact that the channels have separate nodes here, or which properties > are meant for the parent or the child node. Also, some of the "required" > properties are absent in the example, which makes no sense. > I will fix this ambiguity in my v2. > I also assume that some of the properties should just go away: > > * xlnx,device-id should be the argument in the handle from the slave device We can have multiple instances of this VDMA IP configured in the FPGA and we need a unique identifier for each VDMA device that is present in the FPGA. This device-id dt parameter forms the filter mask for the slave devices. As an example, this can be used to get a channel of specific VDMA device (assuming multiple instances) using the API dma_request_channel(). Please note this is an example of a slave device that doesnt have dt node. > * data width should be a property of the slave driver that is configured > through dma_slave_config(), unless you can have dma engines that only > support certain a width. Yes, this VDMA engine soft IP support only certain widths, which is configurable during IP synthesis. Srikanth > > Arnd > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html