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:
reset-names = "serial";
dmas = <&apbdma 8>, <&apbdma 8>;
dma-names = "rx", "tx";
+ nvidia,adjust-baud-rates = <1000000 4000000 136>; /* 1.36% shift */
};