[PATCH 2/4] devicetree: serial: Document msm_serial bindings

[sboyd@codeaurora.org (Stephen Boyd)]

The msm serial device bindings were added to the DTS files but
never documented. Let's document them now and also fix things up
so that it's clearer what hardware is supported. Instead of using
hsuart (for high speed uart), let's use uartdm because that
matches the actual name of the hardware. Also, let's add the
version information in case we need to differentiate between
different versions of the hardware in the future.

Cc: David Brown <davidb@codeaurora.org>
Cc: <devicetree@vger.kernel.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
---
 .../devicetree/bindings/serial/msm_serial.txt      | 82 ++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/msm_serial.txt

diff --git a/Documentation/devicetree/bindings/serial/msm_serial.txt b/Documentation/devicetree/bindings/serial/msm_serial.txt
new file mode 100644
index 0000000..a6efac3
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/msm_serial.txt
@@ -0,0 +1,82 @@
+* MSM Serial UART and UARTDM
+
+There are two MSM serial hardware designs. UARTDM is designed for use with a
+dma engine in high-speed use cases and the non-DM design is for lower speed use
+cases. The two designs are mostly compatible from a software perspective except
+the non-DM design can only read and write one character at a time and so the
+register layout differs slightly.
+
+UART
+----
+Required properties:
+- compatible: Should contain "qcom,msm-uart"
+- reg: Should contain UART register location and length. The first
+       register shall specify the main control registers
+- interrupts: Should contain UART interrupt.
+- clocks: Should contain the core clock.
+- clock-names: Should be "core_clk".
+
+Optional properties:
+- dmas: Should contain dma specifiers for transmit and receive
+- dma-names: Should contain "tx" for transmit and "rx" for receive
+
+Example:
+
+A uart device with dma capabilities.
+
+serial at a9c00000 {
+	compatible = "qcom,msm-uart";
+	reg = <0xa9c00000 0x1000>;
+	interrupts = <11>;
+	clocks = <&uart_cxc>;
+	clock-names = "core_clk";
+	dmas = <&dma0 0>, <&dma0 1>;
+	dma-names = "tx", "rx";
+};
+
+UARTDM
+------
+Required properties:
+- compatible: Should contain at least "qcom,msm-uartdm".
+              A more specific property should be specified as follows depending
+	      on the version:
+		"qcom,msm-uartdm-v1.1"
+		"qcom,msm-uartdm-v1.2"
+		"qcom,msm-uartdm-v1.3"
+		"qcom,msm-uartdm-v1.4"
+- reg: Should contain UART register locations and lengths. The first
+       register shall specify the main control registers. An optional second
+       register location shall specify the GSBI control region.
+- interrupts: Should contain UART interrupt.
+- clocks: Should contain the core clock and the ahb clock.
+- clock-names: Should be "core_clk" for the core clock and "iface_clk" for the
+	       ahb clock.
+
+Optional properties:
+- dmas: Should contain dma specifiers for transmit and receive channels
+- dma-names: Should contain "tx" for transmit and "rx" for receive channels
+
+Examples:
+
+A uartdm v1.4 device with dma capabilities.
+
+serial at f991e000 {
+	compatible = "qcom,msm-uartdm-v1.4", "qcom,msm-uartdm";
+	reg = <0xf991e000 0x1000>;
+	interrupts = <0 108 0x0>;
+	clocks = <&blsp1_uart2_apps_cxc>, <&blsp1_ahb_cxc>;
+	clock-names = "core_clk", "iface_clk";
+	dmas = <&dma0 0>, <&dma0 1>;
+	dma-names = "tx", "rx";
+};
+
+A uartdm v1.3 device without dma capabilities.
+
+serial at 19c40000 {
+	compatible = "qcom,msm-uartdm-v1.3", "qcom,msm-uartdm";
+	reg = <0x19c40000 0x1000>,
+	      <0x19c00000 0x1000>;
+	interrupts = <0 195 0x0>;
+	clocks = <&gsbi5_uart_cxc>, <&gsbi5_ahb_cxc>;
+	clock-names = "core_clk", "iface_clk";
+};
-- 
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