Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 54 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/spi/icpdas-lp8841-spi-rtc.txt b/Documentation/devicetree/bindings/spi/icpdas-lp8841-spi-rtc.txt
new file mode 100644
index 000000000..852b651f3
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+++ b/Documentation/devicetree/bindings/spi/icpdas-lp8841-spi-rtc.txt
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+* ICP DAS LP-8841 SPI Controller for RTC
+
+ICP DAS LP-8841 contains a DS-1302 RTC. RTC is connected to an IO
+memory register, which acts as an SPI master device.
+
+The device uses the standard MicroWire half-duplex transfer timing.
+Master output is set on low clock and sensed by the RTC on the rising
+edge. Master input is set by the RTC on the trailing edge and is sensed
+by the master on low clock.
+
+Required properties:
+
+- #address-cells: should be 1
+
+- #size-cells: should be 0
+
+- compatible: should be "icpdas,lp8841-spi-rtc"
+
+- reg: should provide IO memory address
+
+Requirements to SPI slave nodes:
+
+- There can be only one slave device.
+
+- The spi slave node should claim the following flags which are
+  required by the spi controller.
+
+  - spi-3wire: The master itself has only 3 wire. It cannor work in
+    full duplex mode.
+
+  - spi-cs-high: DS-1302 has active high chip select line. The master
+    doesn't support active low.
+
+  - spi-lsb-first: DS-1302 requires least significant bit first
+    transfers. The master only support this type of bit ordering.
+
+
+Example:
+
+spi@901c {
+	#address-cells = <1>;
+	#size-cells = <0>;
+	compatible = "icpdas,lp8841-spi-rtc";
+	reg = <0x901c 0x1>;
+
+	rtc@0 {
+		compatible = "maxim,ds1302";
+		reg = <0>;
+		spi-max-frequency = <500000>;
+		spi-3wire;
+		spi-lsb-first;
+		spi-cs-high;
+	};
+};