74 lines
2.9 KiB
Plaintext
74 lines
2.9 KiB
Plaintext
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NVIDIA Tegra20/Tegra30 high speed (DMA based) UART controller driver.
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Required properties:
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- compatible : should be,
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"nvidia,tegra20-hsuart" for Tegra20,
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"nvidia,tegra30-hsuart" for Tegra30,
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"nvidia,tegra186-hsuart" for Tegra186,
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"nvidia,tegra194-hsuart" for Tegra194.
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- reg: Should contain UART controller registers location and length.
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- interrupts: Should contain UART controller interrupts.
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- clocks: Must contain one entry, for the module clock.
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See ../clocks/clock-bindings.txt for details.
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- resets : Must contain an entry for each entry in reset-names.
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See ../reset/reset.txt for details.
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- reset-names : Must include the following entries:
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- serial
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- dmas : Must contain an entry for each entry in dma-names.
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See ../dma/dma.txt for details.
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- dma-names : Must include the following entries:
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- rx
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- tx
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Optional properties:
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- nvidia,enable-modem-interrupt: Enable modem interrupts. Should be enable
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only if all 8 lines of UART controller are pinmuxed.
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- nvidia,adjust-baud-rates: List of entries providing percentage of baud rate
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adjustment within a range.
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Each entry contains sets of 3 values. Range low/high and adjusted rate.
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<range_low range_high adjusted_rate>
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When baud rate set on controller falls within the range mentioned in this
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field, baud rate will be adjusted by percentage mentioned here.
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Ex: <9600 115200 200>
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Increase baud rate by 2% when set baud rate falls within range 9600 to 115200
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Baud Rate tolerance:
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Standard UART devices are expected to have tolerance for baud rate error by
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-4 to +4 %. All Tegra devices till Tegra210 had this support. However,
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Tegra186 chip has a known hardware issue. UART Rx baud rate tolerance level
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is 0% to +4% in 1-stop config. Otherwise, the received data will have
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corruption/invalid framing errors. Parker errata suggests adjusting baud
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rate to be higher than the deviations observed in Tx.
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Tx deviation of connected device can be captured over scope (or noted from
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its spec) for valid range and Tegra baud rate has to be set above actual
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Tx baud rate observed. To do this we use nvidia,adjust-baud-rates
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As an example, consider there is deviation observed in Tx for baud rates as
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listed below.
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0 to 9600 has 1% deviation
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9600 to 115200 2% deviation
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This slight deviation is expcted and Tegra UART is expected to handle it. Due
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to the issue stated above, baud rate on Tegra UART should be set equal to or
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above deviation observed for avoiding frame errors.
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Property should be set like this
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nvidia,adjust-baud-rates = <0 9600 100>,
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<9600 115200 200>;
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Example:
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serial@70006000 {
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compatible = "nvidia,tegra30-hsuart", "nvidia,tegra20-hsuart";
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reg = <0x70006000 0x40>;
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reg-shift = <2>;
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interrupts = <0 36 0x04>;
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nvidia,enable-modem-interrupt;
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clocks = <&tegra_car 6>;
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resets = <&tegra_car 6>;
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reset-names = "serial";
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dmas = <&apbdma 8>, <&apbdma 8>;
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dma-names = "rx", "tx";
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nvidia,adjust-baud-rates = <1000000 4000000 136>; /* 1.36% shift */
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};
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