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The i.MX UART peripheral uses the RST_B signal as input, and CTS_B as output. This is just like the DCE role in RS-232. This is true regardless of the "DTE mode" setting of this peripheral. As a result, rs485 support hardware must use the CTS_B signal to control the RS-485 transceiver. This is in contrast to generic rs485 kernel code, documentation, and DT property names that consistently refer to the RTS as transceiver control signal. Add a note in the DT binding document about that, to reduce the confusion somewhat. Signed-off-by: Baruch Siach <baruch@tkos.co.il> Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
37 lines
1.1 KiB
Plaintext
37 lines
1.1 KiB
Plaintext
* Freescale i.MX Universal Asynchronous Receiver/Transmitter (UART)
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Required properties:
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- compatible : Should be "fsl,<soc>-uart"
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- reg : Address and length of the register set for the device
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- interrupts : Should contain uart interrupt
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Optional properties:
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- fsl,dte-mode : Indicate the uart works in DTE mode. The uart works
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in DCE mode by default.
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- rs485-rts-delay, rs485-rts-active-low, rs485-rx-during-tx,
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linux,rs485-enabled-at-boot-time: see rs485.txt. Note that for RS485
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you must enable either the "uart-has-rtscts" or the "rts-gpios"
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properties. In case you use "uart-has-rtscts" the signal that controls
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the transceiver is actually CTS_B, not RTS_B. CTS_B is always output,
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and RTS_B is input, regardless of dte-mode.
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Please check Documentation/devicetree/bindings/serial/serial.txt
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for the complete list of generic properties.
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Note: Each uart controller should have an alias correctly numbered
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in "aliases" node.
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Example:
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aliases {
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serial0 = &uart1;
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};
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uart1: serial@73fbc000 {
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compatible = "fsl,imx51-uart", "fsl,imx21-uart";
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reg = <0x73fbc000 0x4000>;
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interrupts = <31>;
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uart-has-rtscts;
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fsl,dte-mode;
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};
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