1# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) 2%YAML 1.2 3--- 4$id: http://devicetree.org/schemas/serial/nvidia,tegra20-hsuart.yaml# 5$schema: http://devicetree.org/meta-schemas/core.yaml# 6 7title: NVIDIA Tegra20/Tegra30 high speed (DMA based) UART controller driver 8 9maintainers: 10 - Thierry Reding <thierry.reding@gmail.com> 11 - Jon Hunter <jonathanh@nvidia.com> 12 13properties: 14 compatible: 15 oneOf: 16 - enum: 17 - nvidia,tegra20-hsuart 18 - nvidia,tegra30-hsuart 19 - nvidia,tegra186-hsuart 20 - nvidia,tegra194-hsuart 21 - items: 22 - const: nvidia,tegra124-hsuart 23 - const: nvidia,tegra30-hsuart 24 25 reg: 26 maxItems: 1 27 28 interrupts: 29 maxItems: 1 30 31 clocks: 32 items: 33 - description: module clock 34 35 resets: 36 items: 37 - description: module reset 38 39 reset-names: 40 items: 41 - const: serial 42 43 dmas: 44 items: 45 - description: DMA channel used for reception 46 - description: DMA channel used for transmission 47 48 dma-names: 49 items: 50 - const: rx 51 - const: tx 52 53 nvidia,enable-modem-interrupt: 54 $ref: /schemas/types.yaml#/definitions/flag 55 description: Enable modem interrupts. Should be enable only if all 8 lines of UART controller 56 are pinmuxed. 57 58 nvidia,adjust-baud-rates: 59 $ref: /schemas/types.yaml#/definitions/uint32-matrix 60 description: | 61 List of entries providing percentage of baud rate adjustment within a range. Each entry 62 contains a set of 3 values: range low/high and adjusted rate. When the baud rate set on the 63 controller falls within the range mentioned in this field, the baud rate will be adjusted by 64 percentage mentioned here. 65 66 Example: <9600 115200 200> 67 68 Increase baud rate by 2% when set baud rate falls within range 9600 to 115200. 69 70 Standard UART devices are expected to have tolerance for baud rate error by -4 to +4 %. All 71 Tegra devices till Tegra210 had this support. However, Tegra186 chip has a known hardware 72 issue. UART RX baud rate tolerance level is 0% to +4% in 1-stop config. Otherwise, the 73 received data will have corruption/invalid framing errors. Parker errata suggests adjusting 74 baud rate to be higher than the deviations observed in TX. 75 76 TX deviation of connected device can be captured over scope (or noted from its spec) for 77 valid range and Tegra baud rate has to be set above actual TX baud rate observed. To do this 78 we use nvidia,adjust-baud-rates. 79 80 As an example, consider there is deviation observed in TX for baud rates as listed below. 0 81 to 9600 has 1% deviation 9600 to 115200 2% deviation. This slight deviation is expected and 82 Tegra UART is expected to handle it. Due to the issue stated above, baud rate on Tegra UART 83 should be set equal to or above deviation observed for avoiding frame errors. Property 84 should be set like this: 85 86 nvidia,adjust-baud-rates = <0 9600 100>, 87 <9600 115200 200>; 88 items: 89 items: 90 - description: range lower bound 91 - description: range upper bound 92 - description: adjustment (in permyriad, i.e. 0.01%) 93 94required: 95 - compatible 96 - reg 97 - interrupts 98 - clocks 99 - resets 100 - reset-names 101 - dmas 102 - dma-names 103 104allOf: 105 - $ref: serial.yaml 106 107unevaluatedProperties: false 108 109examples: 110 - | 111 #include <dt-bindings/clock/tegra30-car.h> 112 #include <dt-bindings/interrupt-controller/arm-gic.h> 113 114 serial@70006000 { 115 compatible = "nvidia,tegra30-hsuart"; 116 reg = <0x70006000 0x40>; 117 interrupts = <GIC_SPI 36 IRQ_TYPE_LEVEL_HIGH>; 118 nvidia,enable-modem-interrupt; 119 clocks = <&tegra_car TEGRA30_CLK_UARTA>; 120 resets = <&tegra_car 6>; 121 reset-names = "serial"; 122 dmas = <&apbdma 8>, <&apbdma 8>; 123 dma-names = "rx", "tx"; 124 nvidia,adjust-baud-rates = <1000000 4000000 136>; /* 1.36% shift */ 125 }; 126