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
7 title: NVIDIA Tegra20/Tegra30 high speed (DMA based) UART controller driver
8
9 maintainers:
10 - Thierry Reding <thierry.reding@gmail.com>
11 - Jon Hunter <jonathanh@nvidia.com>
12
13 properties:
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
94 required:
95 - compatible
96 - reg
97 - interrupts
98 - clocks
99 - resets
100 - reset-names
101 - dmas
102 - dma-names
103
104 allOf:
105 - $ref: serial.yaml
106
107 unevaluatedProperties: false
108
109 examples:
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 };
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