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Diffstat (limited to 'Documentation/devicetree/bindings/serial/nvidia,tegra20-hsuart.txt')
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1 files changed, 73 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/serial/nvidia,tegra20-hsuart.txt b/Documentation/devicetree/bindings/serial/nvidia,tegra20-hsuart.txt new file mode 100644 index 000000000..f70930403 --- /dev/null +++ b/Documentation/devicetree/bindings/serial/nvidia,tegra20-hsuart.txt @@ -0,0 +1,73 @@ +NVIDIA Tegra20/Tegra30 high speed (DMA based) UART controller driver. + +Required properties: +- compatible : should be, + "nvidia,tegra20-hsuart" for Tegra20, + "nvidia,tegra30-hsuart" for Tegra30, + "nvidia,tegra186-hsuart" for Tegra186, + "nvidia,tegra194-hsuart" for Tegra194. + +- reg: Should contain UART controller registers location and length. +- interrupts: Should contain UART controller interrupts. +- clocks: Must contain one entry, for the module clock. + See ../clocks/clock-bindings.txt for details. +- resets : Must contain an entry for each entry in reset-names. + See ../reset/reset.txt for details. +- reset-names : Must include the following entries: + - serial +- dmas : Must contain an entry for each entry in dma-names. + See ../dma/dma.txt for details. +- dma-names : Must include the following entries: + - rx + - tx + +Optional properties: +- nvidia,enable-modem-interrupt: Enable modem interrupts. Should be enable + only if all 8 lines of UART controller are pinmuxed. +- nvidia,adjust-baud-rates: List of entries providing percentage of baud rate + adjustment within a range. + Each entry contains sets of 3 values. Range low/high and adjusted rate. + <range_low range_high adjusted_rate> + When baud rate set on controller falls within the range mentioned in this + field, baud rate will be adjusted by percentage mentioned here. + Ex: <9600 115200 200> + Increase baud rate by 2% when set baud rate falls within range 9600 to 115200 + +Baud Rate tolerance: + 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>; + +Example: + +serial@70006000 { + compatible = "nvidia,tegra30-hsuart", "nvidia,tegra20-hsuart"; + reg = <0x70006000 0x40>; + reg-shift = <2>; + interrupts = <0 36 0x04>; + nvidia,enable-modem-interrupt; + clocks = <&tegra_car 6>; + 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 */ +}; |