xref: /linux/Documentation/devicetree/bindings/serial/nvidia,tegra20-hsuart.yaml (revision 3a39d672e7f48b8d6b91a09afa4b55352773b4b5)

# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
%YAML 1.2
---
$id: http://devicetree.org/schemas/serial/nvidia,tegra20-hsuart.yaml#
$schema: http://devicetree.org/meta-schemas/core.yaml#

title: NVIDIA Tegra20/Tegra30 high speed (DMA based) UART controller driver

maintainers:
  - Thierry Reding <thierry.reding@gmail.com>
  - Jon Hunter <jonathanh@nvidia.com>

properties:
  compatible:
    oneOf:
      - enum:
          - nvidia,tegra20-hsuart
          - nvidia,tegra30-hsuart
          - nvidia,tegra186-hsuart
          - nvidia,tegra194-hsuart
      - items:
          - const: nvidia,tegra124-hsuart
          - const: nvidia,tegra30-hsuart

  reg:
    maxItems: 1

  interrupts:
    maxItems: 1

  clocks:
    items:
      - description: module clock

  resets:
    items:
      - description: module reset

  reset-names:
    items:
      - const: serial

  dmas:
    items:
      - description: DMA channel used for reception
      - description: DMA channel used for transmission

  dma-names:
    items:
      - const: rx
      - const: tx

  nvidia,enable-modem-interrupt:
    $ref: /schemas/types.yaml#/definitions/flag
    description: Enable modem interrupts. Should be enable only if all 8 lines of UART controller
      are pinmuxed.

  nvidia,adjust-baud-rates:
    $ref: /schemas/types.yaml#/definitions/uint32-matrix
    description: |
      List of entries providing percentage of baud rate adjustment within a range. Each entry
      contains a set of 3 values: range low/high and adjusted rate. When the baud rate set on the
      controller falls within the range mentioned in this field, the baud rate will be adjusted by
      percentage mentioned here.

      Example: <9600 115200 200>

      Increase baud rate by 2% when set baud rate falls within range 9600 to 115200.

      Standard UART devices are expected to have tolerance for baud rate error by -4 to +4 %. All
      Tegra devices till Tegra210 had this support. However, Tegra186 chip has a known hardware
      issue. UART RX baud rate tolerance level is 0% to +4% in 1-stop config. Otherwise, the
      received data will have corruption/invalid framing errors. Parker errata suggests adjusting
      baud rate to be higher than the deviations observed in TX.

      TX deviation of connected device can be captured over scope (or noted from its spec) for
      valid range and Tegra baud rate has to be set above actual TX baud rate observed. To do this
      we use nvidia,adjust-baud-rates.

      As an example, consider there is deviation observed in TX for baud rates as listed below. 0
      to 9600 has 1% deviation 9600 to 115200 2% deviation. This slight deviation is expected and
      Tegra UART is expected to handle it. Due to the issue stated above, baud rate on Tegra UART
      should be set equal to or above deviation observed for avoiding frame errors. Property
      should be set like this:

        nvidia,adjust-baud-rates = <0 9600 100>,
                                   <9600 115200 200>;
    items:
      items:
        - description: range lower bound
        - description: range upper bound
        - description: adjustment (in permyriad, i.e. 0.01%)

required:
  - compatible
  - reg
  - interrupts
  - clocks
  - resets
  - reset-names
  - dmas
  - dma-names

allOf:
  - $ref: serial.yaml

unevaluatedProperties: false

examples:
  - |
    #include <dt-bindings/clock/tegra30-car.h>
    #include <dt-bindings/interrupt-controller/arm-gic.h>

    serial@70006000 {
        compatible = "nvidia,tegra30-hsuart";
        reg = <0x70006000 0x40>;
        interrupts = <GIC_SPI 36 IRQ_TYPE_LEVEL_HIGH>;
        nvidia,enable-modem-interrupt;
        clocks = <&tegra_car TEGRA30_CLK_UARTA>;
        resets = <&tegra_car 6>;
        reset-names = "serial";
        dmas = <&apbdma 8>, <&apbdma 8>;
        dma-names = "rx", "tx";
        nvidia,adjust-baud-rates = <1000000 4000000 136>; /* 1.36% shift */
    };