0001 NVIDIA Tegra20/Tegra30 high speed (DMA based) UART controller driver.
0002
0003 Required properties:
0004 - compatible : should be,
0005 "nvidia,tegra20-hsuart" for Tegra20,
0006 "nvidia,tegra30-hsuart" for Tegra30,
0007 "nvidia,tegra186-hsuart" for Tegra186,
0008 "nvidia,tegra194-hsuart" for Tegra194.
0009
0010 - reg: Should contain UART controller registers location and length.
0011 - interrupts: Should contain UART controller interrupts.
0012 - clocks: Must contain one entry, for the module clock.
0013 See ../clocks/clock-bindings.txt for details.
0014 - resets : Must contain an entry for each entry in reset-names.
0015 See ../reset/reset.txt for details.
0016 - reset-names : Must include the following entries:
0017 - serial
0018 - dmas : Must contain an entry for each entry in dma-names.
0019 See ../dma/dma.txt for details.
0020 - dma-names : Must include the following entries:
0021 - rx
0022 - tx
0023
0024 Optional properties:
0025 - nvidia,enable-modem-interrupt: Enable modem interrupts. Should be enable
0026 only if all 8 lines of UART controller are pinmuxed.
0027 - nvidia,adjust-baud-rates: List of entries providing percentage of baud rate
0028 adjustment within a range.
0029 Each entry contains sets of 3 values. Range low/high and adjusted rate.
0030 <range_low range_high adjusted_rate>
0031 When baud rate set on controller falls within the range mentioned in this
0032 field, baud rate will be adjusted by percentage mentioned here.
0033 Ex: <9600 115200 200>
0034 Increase baud rate by 2% when set baud rate falls within range 9600 to 115200
0035
0036 Baud Rate tolerance:
0037 Standard UART devices are expected to have tolerance for baud rate error by
0038 -4 to +4 %. All Tegra devices till Tegra210 had this support. However,
0039 Tegra186 chip has a known hardware issue. UART Rx baud rate tolerance level
0040 is 0% to +4% in 1-stop config. Otherwise, the received data will have
0041 corruption/invalid framing errors. Parker errata suggests adjusting baud
0042 rate to be higher than the deviations observed in Tx.
0043
0044 Tx deviation of connected device can be captured over scope (or noted from
0045 its spec) for valid range and Tegra baud rate has to be set above actual
0046 Tx baud rate observed. To do this we use nvidia,adjust-baud-rates
0047
0048 As an example, consider there is deviation observed in Tx for baud rates as
0049 listed below.
0050 0 to 9600 has 1% deviation
0051 9600 to 115200 2% deviation
0052 This slight deviation is expcted and Tegra UART is expected to handle it. Due
0053 to the issue stated above, baud rate on Tegra UART should be set equal to or
0054 above deviation observed for avoiding frame errors.
0055 Property should be set like this
0056 nvidia,adjust-baud-rates = <0 9600 100>,
0057 <9600 115200 200>;
0058
0059 Example:
0060
0061 serial@70006000 {
0062 compatible = "nvidia,tegra30-hsuart", "nvidia,tegra20-hsuart";
0063 reg = <0x70006000 0x40>;
0064 reg-shift = <2>;
0065 interrupts = <0 36 0x04>;
0066 nvidia,enable-modem-interrupt;
0067 clocks = <&tegra_car 6>;
0068 resets = <&tegra_car 6>;
0069 reset-names = "serial";
0070 dmas = <&apbdma 8>, <&apbdma 8>;
0071 dma-names = "rx", "tx";
0072 nvidia,adjust-baud-rates = <1000000 4000000 136>; /* 1.36% shift */
0073 };
