Hi Rob, > -----Original Message----- > From: [email protected] [mailto:dmaengine- > [email protected]] On Behalf Of Rob Herring > Sent: Friday, April 22, 2016 9:43 PM > To: Appana Durga Kedareswara Rao <[email protected]> > Cc: [email protected]; [email protected]; > [email protected]; [email protected]; Michal Simek > <[email protected]>; Soren Brinkmann <[email protected]>; > [email protected]; [email protected]; [email protected]; > [email protected]; [email protected]; Anirudha > Sarangi <[email protected]>; Punnaiah Choudary Kalluri > <[email protected]>; [email protected]; linux-arm- > [email protected]; [email protected]; > [email protected] > Subject: Re: [PATCH v6 1/2] Documentation: DT: dma: Add Xilinx zynqmp dma > device tree binding documentation > > On Fri, Apr 22, 2016 at 12:36 AM, Appana Durga Kedareswara Rao > <[email protected]> wrote: > > Hi Rob, > > > > Thanks for the review... > > > >> -----Original Message----- > >> From: Rob Herring [mailto:[email protected]] > >> Sent: Thursday, April 21, 2016 7:12 PM > >> To: Appana Durga Kedareswara Rao <[email protected]> > >> Cc: [email protected]; [email protected]; > >> [email protected]; [email protected]; Michal Simek > >> <[email protected]>; Soren Brinkmann <[email protected]>; > >> [email protected]; [email protected]; Appana Durga > >> Kedareswara Rao <[email protected]>; [email protected]; > >> [email protected]; [email protected]; Anirudha > >> Sarangi <[email protected]>; Punnaiah Choudary Kalluri > >> <[email protected]>; [email protected]; linux-arm- > >> [email protected]; [email protected]; > >> [email protected] > >> 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 <[email protected]> > >> > Signed-off-by: Kedareswara rao Appana <[email protected]> > >> > --- > >> > 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). > > I understand that. That should not really matter if the AXI master properly > sets > byte lane strobes other than defining max burst length which you already have > defined elsewhere. > > > 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; > > Read what I wrote before and read the documentation for these fields. > They are bitmasks.
I misunderstood the question that you asked yesterday. Now I got clarified. Will fix it in the next version of the patch... Thanks for the detailed explanation. Regards, Kedar. > > Rob > -- > To unsubscribe from this list: send the line "unsubscribe dmaengine" in the > body > of a message to [email protected] More majordomo info at > http://vger.kernel.org/majordomo-info.html
