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| author | Baruch Siach <baruch@tkos.co.il> | 2018-06-28 10:25:32 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-06-28 15:02:38 +0300 |
| commit | e51e597d9f692cd7d205e3b44bb35ea3b97e7329 (patch) | |
| tree | 314792571aa41514184f9f098b4513ce4f64980a /Documentation | |
| parent | 728e74a46fd4166935f2079b619007eaad98c9a5 (diff) | |
| download | linux-e51e597d9f692cd7d205e3b44bb35ea3b97e7329.tar.xz | |
dt-bindings: serial: imx: clarify rs485 support usage
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>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/devicetree/bindings/serial/fsl-imx-uart.txt | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/Documentation/devicetree/bindings/serial/fsl-imx-uart.txt b/Documentation/devicetree/bindings/serial/fsl-imx-uart.txt index afcfbc34e243..35957cbf1571 100644 --- a/Documentation/devicetree/bindings/serial/fsl-imx-uart.txt +++ b/Documentation/devicetree/bindings/serial/fsl-imx-uart.txt @@ -9,7 +9,11 @@ Optional properties: - fsl,dte-mode : Indicate the uart works in DTE mode. The uart works in DCE mode by default. - rs485-rts-delay, rs485-rts-active-low, rs485-rx-during-tx, - linux,rs485-enabled-at-boot-time: see rs485.txt + linux,rs485-enabled-at-boot-time: see rs485.txt. Note that for RS485 + you must enable either the "uart-has-rtscts" or the "rts-gpios" + properties. In case you use "uart-has-rtscts" the signal that controls + the transceiver is actually CTS_B, not RTS_B. CTS_B is always output, + and RTS_B is input, regardless of dte-mode. Please check Documentation/devicetree/bindings/serial/serial.txt for the complete list of generic properties. |