dt-bindings: spi_qsd: Add documentation of SPI BLSP driver

Qualcomm Technologies, Inc. Serial Peripheral Interface (SPI)

Required properties:

- compatible : Should be "qcom,spi-qup-v2".

- reg : Offset and length of the register regions for the device

- reg-names : Register region names referenced in reg above.

	Required register resource entries are:

	"spi_physical" : Physical address of controller register blocks.

- interrupts : Interrupt numbers used by this controller

- interrupt-names : Interrupt resource names referenced in interrupts above.

	Required interrupt resource entries are:

	"spi_irq" : QUP-core interrupt.

- spi-max-frequency : Specifies maximum SPI clock frequency, Units - Hz.

Required alias:

- The desired bus-number is specified via an alias with the following format

	'spi{n}' where n is the bus number.

Optional properties:

- qcom,gpio-mosi : GPIO pin number of the MOSI bus line.

- qcom,gpio-miso : GPIO pin number of the MISO bus line.

- qcom,gpio-clk  : GPIO pin number of the CLK  bus line.

- qcom,gpio-cs0  : GPIO pin number of the chipselect0 bus line.

- qcom,gpio-cs1  : GPIO pin number of the chipselect1 bus line.

- qcom,gpio-cs2  : GPIO pin number of the chipselect2 bus line.

- qcom,gpio-cs3  : GPIO pin number of the chipselect3 bus line.

- qcom,infinite-mode: When missing or set to zero, QUP uses infinite-mode. When

  value is non-zero, the value is the number of words in maximum transfer

  length.

 - qcom,active-only : Vote for core clock when the application processor goes

  to active state and remove that vote when it goes to idle state. This flag may

  improve service time of first spi request at the expense of power consumption.

  When this entry is not present, voting is done by the runtime-pm callbacks.

 - qcom,master-id : Master endpoint number used for voting on clocks using the

  bus-scaling driver.

 - qcom,rt-priority : whether spi message queue is set to run as a realtime task.

  With this spi transaction message pump with high (realtime) priority to reduce

  the transfer latency on the bus by minimising the delay between a transfer request

 - qcom,shared : whether this qup is shared with other ee's

Optional properties which are required for support of BAM-mode:

- qcom,ver-reg-exists : Boolean. When present, allows driver to verify if HW

  version support latest features (e.g. BAM) and then enable them. Should be

  removed for legacy HW.

- qcom,use-bam : Boolean. When present, enables BAM-mode.

- qcom,use-pinctrl : Boolean. When present, enables pinctrl frame work to configure GPIO's

  instead of existing gpio mux hence gpio entries are no more required if present.

- pinctrl-names : Property must contain "spi_default" and "spi_sleep" if

  pinctrl is to be used.

  instead of existing gpio mux hence gpio entries are no more required if present.

- qcom,bam-consumer-pipe-index : BAM consumer-pipe index.

- qcom,bam-producer-pipe-index : BAM producer-pipe index.

- reg-names : register region names referenced in reg.

	Required register resource for BAM are:

	"spi_bam_physical" : Physical address of BAM for this controller.

- interrupt-names : interrupt resource names referenced in interrupts.

	Required interrupt resource from BAM are:

	"spi_bam_irq" : BAM interrupt used by the controller.

Optional SPI slave nodes must be children of the SPI master node and contain

the following properties.

- reg: (required) chip-select address of the device.

- compatible : (required) Name of SPI device following generic names.

- spi-max-frequency : (required) Maximum SPI clocking speed of device in Hz

- interrupts : (recommended) Should contain the SPI slave interrupt number

  encoded depending on the type of the interrupt controller.

- interrupt-parent : (recommended) The phandle for the interrupt controller

  that services interrupts for this device.

- spi-cpol : (optional) Empty property indicating device requires inverse

  clock polarity (CPOL) mode

- spi-cpha : (optional) Empty property indicating device requires shifted

  clock phase (CPHA) mode

- spi-cs-high : (optional) Empty property indicating device requires

  chip select active high

Example:

	aliases {

		spi0 = &spi_0;

	};

	spi_0: spi@f9923000 {

		compatible = "qcom,spi-qup-v2";

		reg-names = "spi_physical", "spi_bam_physical";

		reg = <0xf9923000 0x1000>,

			<0xf9904000 0x10000>;

		interrupt-names = "spi_irq", "spi_bam_irq";

		interrupts = <0 95 0>, <0 238 0>;

		spi-max-frequency = <19200000>;

		#address-cells = <1>;

		#size-cells = <0>;

		qcom,gpio-mosi = <&msmgpio 0 0>;

		qcom,gpio-miso = <&msmgpio 1 0>;

		qcom,gpio-clk  = <&msmgpio 3 0>;

		qcom,gpio-cs2  = <&msmgpio 9 0>;

		qcom,infinite-mode = <0>;

		qcom,use-bam;

		qcom,use-pinctrl;

		qcom,bam-consumer-pipe-index = <12>;

		qcom,bam-producer-pipe-index = <13>;

		qcom,ver-reg-exists;

		qcom,master-id = <86>;

		qcom,rt-priority;

	};