Kernel-4.18.0-80.el8_atmel-usart

• Atmel Universal Synchronous Asynchronous Receiver/Transmitter (USART)

Required properties:

• compatible: Should be “atmel,-usart” or “atmel,-dbgu”
  The compatible indicated will be the first SoC to support an
  additional mode or an USART new feature.
  For the dbgu UART, use “atmel,-dbgu”, “atmel,-usart”
• reg: Should contain registers location and length
• interrupts: Should contain interrupt
• clock-names: tuple listing input clock names.
  Required elements: “usart”
• clocks: phandles to input clocks.

Optional properties:

• atmel,use-dma-rx: use of PDC or DMA for receiving data
• atmel,use-dma-tx: use of PDC or DMA for transmitting data
• {rts,cts,dtr,dsr,rng,dcd}-gpios: specify a GPIO for RTS/CTS/DTR/DSR/RI/DCD line respectively.
  It will use specified PIO instead of the peripheral function pin for the USART feature.
  If unsure, don’t specify this property.
• add dma bindings for dma transfer:
  • dmas: DMA specifier, consisting of a phandle to DMA controller node,
    memory peripheral interface and USART DMA channel ID, FIFO configuration.
    Refer to dma.txt and atmel-dma.txt for details.
  • dma-names: “rx” for RX channel, “tx” for TX channel.
• atmel,fifo-size: maximum number of data the RX and TX FIFOs can store for FIFO
  capable USARTs.
• rs485-rts-delay, rs485-rx-during-tx, linux,rs485-enabled-at-boot-time: see rs485.txt

compatible description:

• at91rm9200: legacy USART support
• at91sam9260: generic USART implementation for SAM9 SoCs

Example:

• use PDC:
  usart0: serial@fff8c000 {

    compatible = "atmel,at91sam9260-usart";
    reg = <0xfff8c000 0x4000>;
    interrupts = <7>;
    clocks = <&usart0_clk>;
    clock-names = "usart";
    atmel,use-dma-rx;
    atmel,use-dma-tx;
    rts-gpios = <&pioD 15 GPIO_ACTIVE_LOW>;
    cts-gpios = <&pioD 16 GPIO_ACTIVE_LOW>;
    dtr-gpios = <&pioD 17 GPIO_ACTIVE_LOW>;
    dsr-gpios = <&pioD 18 GPIO_ACTIVE_LOW>;
    dcd-gpios = <&pioD 20 GPIO_ACTIVE_LOW>;
    rng-gpios = <&pioD 19 GPIO_ACTIVE_LOW>;
  

  };

• use DMA:
  usart0: serial@f001c000 {

    compatible = "atmel,at91sam9260-usart";
    reg = <0xf001c000 0x100>;
    interrupts = <12 4 5>;
    clocks = <&usart0_clk>;
    clock-names = "usart";
    atmel,use-dma-rx;
    atmel,use-dma-tx;
    dmas = <&dma0 2 0x3>,
           <&dma0 2 0x204>;
    dma-names = "tx", "rx";
    atmel,fifo-size = <32>;
  

  };