Hi Rob, Thanks for the review... > -----Original Message----- > From: Rob Herring [mailto:robh@xxxxxxxxxx] > Sent: Thursday, April 21, 2016 7:12 PM > To: Appana Durga Kedareswara Rao <appanad@xxxxxxxxxx> > Cc: pawel.moll@xxxxxxx; mark.rutland@xxxxxxx; > ijc+devicetree@xxxxxxxxxxxxxx; galak@xxxxxxxxxxxxxx; Michal Simek > <michals@xxxxxxxxxx>; Soren Brinkmann <sorenb@xxxxxxxxxx>; > vinod.koul@xxxxxxxxx; dan.j.williams@xxxxxxxxx; Appana Durga Kedareswara > Rao <appanad@xxxxxxxxxx>; moritz.fischer@xxxxxxxxx; > laurent.pinchart@xxxxxxxxxxxxxxxx; luis@xxxxxxxxxxxxxxxxx; Anirudha > Sarangi <anirudh@xxxxxxxxxx>; Punnaiah Choudary Kalluri > <punnaia@xxxxxxxxxx>; devicetree@xxxxxxxxxxxxxxx; linux-arm- > kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > dmaengine@xxxxxxxxxxxxxxx > Subject: Re: [PATCH v6 1/2] Documentation: DT: dma: Add Xilinx zynqmp dma > device tree binding documentation > > On Fri, Apr 15, 2016 at 02:22:53PM +0530, Kedareswara rao Appana wrote: > > Device-tree binding documentation for Xilinx zynqmp dma engine used in > > Zynq UltraScale+ MPSoC. > > > > Signed-off-by: Punnaiah Choudary Kalluri <punnaia@xxxxxxxxxx> > > Signed-off-by: Kedareswara rao Appana <appanad@xxxxxxxxxx> > > --- > > Changes in v6: > > - Removed desc-axi-cache/dst-axi-cache/src-axi-cache properties > > from the binding doc as it allow broken combinations when dma-coherent > > is set as suggested by Rob. > > - Fixed minor comments given by Rob related coding(lower case DT node > name). > > Changes in v5: > > - Use dma-coherent flag for coherent transfers as suggested by rob. > > - Removed unnecessary properties from binding doc as suggested by Rob. > > Changes in v4: > > - None > > Changes in v3: > > - None > > Changes in v2: > > - None. > > > > .../devicetree/bindings/dma/xilinx/zynqmp_dma.txt | 44 > ++++++++++++++++++++++ > > 1 file changed, 44 insertions(+) > > create mode 100644 > Documentation/devicetree/bindings/dma/xilinx/zynqmp_dma.txt > > > > diff --git a/Documentation/devicetree/bindings/dma/xilinx/zynqmp_dma.txt > b/Documentation/devicetree/bindings/dma/xilinx/zynqmp_dma.txt > > new file mode 100644 > > index 0000000..f0f0b54 > > --- /dev/null > > +++ b/Documentation/devicetree/bindings/dma/xilinx/zynqmp_dma.txt > > @@ -0,0 +1,44 @@ > > +Xilinx ZynqMP DMA engine, it does support memory to memory transfers, > > +memory to device and device to memory transfers. It also has flow > > +control and rate control support for slave/peripheral dma access. > > + > > +Required properties: > > +- compatible : Should be "xlnx,zynqmp-dma-1.0" > > +- reg : Memory map for gdma/adma module access. > > +- interrupt-parent : Interrupt controller the interrupt is routed through > > +- interrupts : Should contain DMA channel interrupt. > > +- xlnx,bus-width : Axi buswidth in bits. Should contain 128 or 64 > > I think how this is getting used by the driver is wrong. > {src,dst}_addr_widths are supposed to be a bitmask of supported slave > device register widths. You aren't doing a bitmask and you are also > saying you only support slaves with 8 or 16 byte data registers which is > somewhat rare. It may happen to work because 128/8 == BIT(4). However, > the documentation for the field is contradictory in that it says 1,2,4 > or 8 byte widths are supported, but the enum has more sizes. The DMA supports an AXI bus width of 128/64 bits only. Please refer IP data sheet. http://www.xilinx.com/support/documentation/user_guides/ug1085-zynq-ultrascale-trm.pdf Page No: 359(DMA Over fetch section). That's why during probe we are making the dma_device supported source and destination address widths accordingly based on the DT property. Snap shot of driver code from the probe: struct dma_device *p; p->dst_addr_widths = zdev->chan->bus_width / 8; p->src_addr_widths = zdev->chan->bus_width / 8; Where bus_width property is read from the probe. err = of_property_read_u32(node, "xlnx,bus-width", &chan->bus_width) Cheers!, Kedar... > > Rob -- 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
