linux-kernel - Re: [PATCH v2 5/5] devicetree: zynqmp_ps_pcie: Devicetree binding for Root DMA

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Message-ID: <20170913202534.vf4r7dmuyfectbmv@rob-hp-laptop>
Date:   Wed, 13 Sep 2017 15:25:34 -0500
From:   Rob Herring <robh@...nel.org>
To:     Ravi Shankar Jonnalagadda <venkata.ravi.jonnalagadda@...inx.com>
Cc:     vinod.koul@...el.com, mark.rutland@....com,
        michal.simek@...inx.com, soren.brinkmann@...inx.com,
        dan.j.williams@...el.com, bhelgaas@...gle.com, vjonnal@...inx.com,
        lorenzo.pieralisi@....com, bharat.kumar.gogada@...inx.com,
        dmaengine@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, rgummal@...inx.com
Subject: Re: [PATCH v2 5/5] devicetree: zynqmp_ps_pcie: Devicetree binding
 for Root DMA

On Fri, Sep 08, 2017 at 05:53:08PM +0530, Ravi Shankar Jonnalagadda wrote:
> Binding explaining devicetree usage for enabling Root DMA capability
> 
> Signed-off-by: Ravi Shankar Jonnalagadda <vjonnal@...inx.com>
> Signed-off-by: RaviKiran Gummaluri <rgummal@...inx.com>
> ---
>  .../devicetree/bindings/dma/xilinx/ps-pcie-dma.txt | 67 ++++++++++++++++++++++
>  1 file changed, 67 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/dma/xilinx/ps-pcie-dma.txt
> 
> diff --git a/Documentation/devicetree/bindings/dma/xilinx/ps-pcie-dma.txt b/Documentation/devicetree/bindings/dma/xilinx/ps-pcie-dma.txt
> new file mode 100644
> index 0000000..1522a49
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/dma/xilinx/ps-pcie-dma.txt
> @@ -0,0 +1,67 @@
> +* 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 "xlnx,ps_pcie_regbase"

*-names for a single entry is pointless.

> +- interrupts: Interrupt pin for Root DMA
> +- interrupt-names: Name for the interrupt. Should be "xlnx,ps_pcie_rootdma_intr"

ditto

> +- interrupt-parent: Should be gic in case of zynqmp
> +- xlnx,rootdma: Indicates this platform device is root dma.
> +	This is required as the same platform driver will be invoked by pcie end points too

platform device and driver are Linux terms.

> +- xlnx,dma_vendorid: 16 bit PCIe device vendor id.
> +	This can be later used by dma client for matching while using dma_request_channel
> +- xlnx,dma_deviceid: 16 bit PCIe device id
> +	This can be later used by dma client for matching while using dma_request_channel

This is the id's of the client? Sounds like you should use the DMA 
binding.

> +- xlnx,numchannels: Indicates number of channels to be enabled for the device.
> +	Valid values are from 1 to 4 for zynqmp

DMA binding has a similar property.

> +- xlnx,ps_pcie_channel : One for each channel to be enabled.

s/_/-/

> +	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: Coaelse 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: Coaelse 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@...f0000 {

dma-controller@...

> +		compatible = "xlnx,ps_pcie_dma-1.00.a";
> +		reg = <0x0 0xfd0f0000 0x0 0x1000>;
> +		reg-names = "xlnx,ps_pcie_regbase";
> +		interrupts = <0 117 4>;
> +		interrupt-names = "xlnx,ps_pcie_rootdma_intr";
> +		interrupt-parent = <&gic>;
> +		xlnx,rootdma;
> +		xlnx,dma_vendorid = /bits/ 16 <0x10EE>;
> +		xlnx,dma_deviceid = /bits/ 16 <0xD021>;
> +		xlnx,numchannels = <0x4>;
> +		#size-cells = <0x5>;
> +		xlnx,ps_pcie_channel0 = <0x1 0x7CF 0x4 0x0 0x3E8>;
> +		xlnx,ps_pcie_channel1 = <0x0 0x7CF 0x4 0x0 0x3E8>;
> +		xlnx,ps_pcie_channel2 = <0x1 0x7CF 0x4 0x0 0x3E8>;
> +		xlnx,ps_pcie_channel3 = <0x0 0x7CF 0x4 0x0 0x3E8>;
> +    };
> -- 
> 2.7.4
> 
> --
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