| # 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 expcted 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%) |
| |
| allOf: |
| - $ref: serial.yaml |
| |
| unevaluatedProperties: false |
| |
| required: |
| - compatible |
| - reg |
| - interrupts |
| - clocks |
| - resets |
| - reset-names |
| - dmas |
| - dma-names |
| |
| 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 */ |
| }; |
