1* Atmel Universal Synchronous Asynchronous Receiver/Transmitter (USART)
2
3Required properties:
4- compatible: Should be "atmel,<chip>-usart" or "atmel,<chip>-dbgu"
5  The compatible <chip> indicated will be the first SoC to support an
6  additional mode or an USART new feature.
7  For the dbgu UART, use "atmel,<chip>-dbgu", "atmel,<chip>-usart"
8- reg: Should contain registers location and length
9- interrupts: Should contain interrupt
10- clock-names: tuple listing input clock names.
11	Required elements: "usart"
12- clocks: phandles to input clocks.
13
14Optional properties:
15- atmel,use-dma-rx: use of PDC or DMA for receiving data
16- atmel,use-dma-tx: use of PDC or DMA for transmitting data
17- {rts,cts,dtr,dsr,rng,dcd}-gpios: specify a GPIO for RTS/CTS/DTR/DSR/RI/DCD line respectively.
18  It will use specified PIO instead of the peripheral function pin for the USART feature.
19  If unsure, don't specify this property.
20- add dma bindings for dma transfer:
21	- dmas: DMA specifier, consisting of a phandle to DMA controller node,
22		memory peripheral interface and USART DMA channel ID, FIFO configuration.
23		Refer to dma.txt and atmel-dma.txt for details.
24	- dma-names: "rx" for RX channel, "tx" for TX channel.
25- atmel,fifo-size: maximum number of data the RX and TX FIFOs can store for FIFO
26  capable USARTs.
27- rs485-rts-delay, rs485-rx-during-tx, linux,rs485-enabled-at-boot-time: see rs485.txt
28
29<chip> compatible description:
30- at91rm9200:  legacy USART support
31- at91sam9260: generic USART implementation for SAM9 SoCs
32
33Example:
34- use PDC:
35	usart0: serial@fff8c000 {
36		compatible = "atmel,at91sam9260-usart";
37		reg = <0xfff8c000 0x4000>;
38		interrupts = <7>;
39		clocks = <&usart0_clk>;
40		clock-names = "usart";
41		atmel,use-dma-rx;
42		atmel,use-dma-tx;
43		rts-gpios = <&pioD 15 GPIO_ACTIVE_LOW>;
44		cts-gpios = <&pioD 16 GPIO_ACTIVE_LOW>;
45		dtr-gpios = <&pioD 17 GPIO_ACTIVE_LOW>;
46		dsr-gpios = <&pioD 18 GPIO_ACTIVE_LOW>;
47		dcd-gpios = <&pioD 20 GPIO_ACTIVE_LOW>;
48		rng-gpios = <&pioD 19 GPIO_ACTIVE_LOW>;
49	};
50
51- use DMA:
52	usart0: serial@f001c000 {
53		compatible = "atmel,at91sam9260-usart";
54		reg = <0xf001c000 0x100>;
55		interrupts = <12 4 5>;
56		clocks = <&usart0_clk>;
57		clock-names = "usart";
58		atmel,use-dma-rx;
59		atmel,use-dma-tx;
60		dmas = <&dma0 2 0x3>,
61		       <&dma0 2 0x204>;
62		dma-names = "tx", "rx";
63		atmel,fifo-size = <32>;
64	};
65