On Sun, Apr 17, 2016 at 03:14:34PM +0200, Arnd Bergmann wrote: > On Tuesday 12 April 2016 09:03:38 Rob Herring wrote: > > On Mon, Apr 11, 2016 at 01:11:46PM +0530, Nava kishore Manne wrote: > > > This patch updates the driver to support 64-bit DMA > > > addressing. > > > > > > Signed-off-by: Nava kishore Manne <navam@xxxxxxxxxx> > > > --- > > > .../devicetree/bindings/usb/udc-xilinx.txt | 3 +- > > > drivers/usb/gadget/udc/udc-xilinx.c | 38 ++++++++++++++++++++-- > > > 2 files changed, 37 insertions(+), 4 deletions(-) > > > > > > diff --git a/Documentation/devicetree/bindings/usb/udc-xilinx.txt b/Documentation/devicetree/bindings/usb/udc-xilinx.txt > > > index 47b4e39..d417872 100644 > > > --- a/Documentation/devicetree/bindings/usb/udc-xilinx.txt > > > +++ b/Documentation/devicetree/bindings/usb/udc-xilinx.txt > > > @@ -7,12 +7,13 @@ Required properties: > > > - interrupts : Should contain single irq line of USB2 device > > > controller > > > - xlnx,has-builtin-dma : if DMA is included > > > - > > > +- xlnx,addrwidth : Should be the dma addressing size in bits(ex: 40 bits). > > > > Now this property shows up in a 2nd device. Now I'm more convinced this > > is the wrong approach and should use dma-ranges. > > Not necessarily: We need to be careful not to mix up two different things here: > > * dma-ranges describes the address width of a bus, along with possible offsets. > In order to do wider than 32-bit addressing, all upstream busses must be > capable of supporting this, and AXI can have either 64-bit or 32-bit addressing. > > * A device may have a register set that allows wider DMA. This is normally > identified through the 'compatible' property, and you can have all > combinations with bus addressing: a device with 32-bit DMA can be connected > to a 64-bit AXI bus, and a device with 64-bit DMA can have an upstream parent > or grandparent that is limited to 32 bits (or any other width really). > > The patch here is almost certainly wrong. For one thing, it never sets the > DMA mask to the correct value, and it also infers the presence of the > 0x308..0x317 register range from an arbitrary DT property that describes > something else (the supported width of the DMA). Right, you don't need to know the exact bus width for determining the register/descriptor set is 32 or 64 bit addesses. I'm fine with a property for that, but if limiting the actual connected address bits is needed, then dma-ranges should be used. 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
