PCI: ZYNQMP PS PCIe Driver: Root DMA dt bindings

Added device tree bindings for enabling root dma

Signed-off-by: Ravi Shankar Jonnalagadda <vjonnal@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

diff --git a/Documentation/devicetree/bindings/dma/xilinx/ps-pcie-dma.txt b/Documentation/devicetree/bindings/dma/xilinx/ps-pcie-dma.txt
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+* Xilinx PS PCIe Root DMA
+
+Required properties:
+- compatible: Should be "xlnx,ps_pcie_dma-1.00.a"
+- reg: Register offset for Root DMA channels
+- reg-names: Name for the register. Should be "ps_pcie_regbase"
+- interrupts: Interrupt pin for Root DMA
+- interrupt-names: Name for the interrupt. Should be "ps_pcie_rootdma_intr"
+- interrupt-parent: Should be gic in case of zynqmp
+- rootdma: Indicates this platform device is root dma.
+       This is required as the same platform driver will be invoked by pcie end points too
+- dma_vendorid: 16 bit PCIe device vendor id.
+       This can be later used by dma client for matching while using dma_request_channel
+- dma_deviceid: 16 bit PCIe device id
+       This can be later used by dma client for matching while using dma_request_channel
+- numchannels: Indicates number of channels to be enabled for the device.
+       Valid values are from 1 to 4 for zynqmp
+- ps_pcie_channel : One for each channel to be enabled.
+       This array contains channel specific properties.
+       Index 0: Direction of channel
+               Direction of channel can be either PCIe Memory to AXI memory i.e., Host to Card or
+               AXI Memory to PCIe memory i.e., Card to Host
+               PCIe to AXI Channel Direction is represented as 0x1
+               AXI to PCIe Channel Direction is represented as 0x0
+       Index 1: Number of Buffer Descriptors
+               This number describes number of buffer descriptors to be allocated for a channel
+       Index 2: Number of Queues
+               Each Channel has four DMA Buffer Descriptor Queues.
+               By default All four Queues will be managed by Root DMA driver.
+               User may choose to have only two queues either Source and it's Status Queue or
+                       Destination and it's Status Queue to be handled by Driver.
+               The other two queues need to be handled by user logic which will not be part of this driver.
+               All Queues on Host is represented by 0x4
+               Two Queues on Host is represented by 0x2
+       Index 3: Coalesce Count
+               This number indicates the number of transfers after which interrupt needs to
+               be raised for the particular channel. The allowed range is from 0 to 255
+       Index 4: Coalesce Count Timer frequency
+               This property is used to control the frequency of poll timer. Poll timer is
+               created for a channel whenever coalesce count value (>= 1) is programmed for the particular
+               channel. This timer is helpful in draining out completed transactions even though interrupt is
+               not generated.
+
+Client Usage:
+       DMA clients can request for these channels using dma_request_channel API
+
+
+Xilinx PS PCIe Root DMA node Example
+++++++++++++++++++++++++++++++++++++
+
+       pci_rootdma: rootdma@fd0f0000 {
+               compatible = "xlnx,ps_pcie_dma-1.00.a";
+               reg = <0x0 0xfd0f0000 0x0 0x1000>;
+               reg-names = "ps_pcie_regbase";
+               interrupts = <0 117 4>;
+               interrupt-names = "ps_pcie_rootdma_intr";
+               interrupt-parent = <&gic>;
+               rootdma;
+               dma_vendorid = /bits/ 16 <0x10EE>;
+               dma_deviceid = /bits/ 16 <0xD021>;
+               numchannels = <0x4>;
+               #size-cells = <0x5>;
+               ps_pcie_channel0 = <0x1 0x7CF 0x4 0x0 0x3E8>;
+               ps_pcie_channel1 = <0x0 0x7CF 0x4 0x0 0x3E8>;
+               ps_pcie_channel2 = <0x1 0x7CF 0x4 0x0 0x3E8>;
+               ps_pcie_channel3 = <0x0 0x7CF 0x4 0x0 0x3E8>;
+    };