add draft dts for LTC2947 on SPI1

- use BB-SPIDEV1-00A0.dts as template

- revise according to examples on the [Analog Devices wiki][1]

[1]: https://wiki.analog.com/resources/tools-software/linux-drivers/hwmon/ltc2947#example_i2c_spi_device_initialization

1 files changed, 99 insertions, 0 deletions

diff --git a/src/arm/BB-SPI1-LTC2947-00A0.dts b/src/arm/BB-SPI1-LTC2947-00A0.dts
new file mode 100644
index 0000000..717a37a
--- /dev/null
+++ b/src/arm/BB-SPI1-LTC2947-00A0.dts
@@ -0,0 +1,99 @@
+/*
+ * Copyright (C) 2020 Otter Works
+ *
+ * LTC2947 on SPI1
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+/dts-v1/;
+/plugin/;
+
+#include <dt-bindings/board/am335x-bbw-bbb-base.h>
+#include <dt-bindings/pinctrl/am33xx.h>
+
+/ {
+	compatible = "ti,beaglebone", "ti,beaglebone-black", "ti,beaglebone-green";
+
+	/* identification */
+	part-number = "BB-SPI1-LTC2947";
+	version = "00A0";
+
+	/* state the resources this cape uses */
+	exclusive-use =
+		/* the pin header uses */
+		"P9.31",	/* spi1_sclk */
+		"P9.29",	/* spi1_d0 */
+		"P9.30",	/* spi1_d1 */
+		"P9.28",	/* spi1_cs0 */
+		/* the hardware ip uses */
+		"spi1";
+
+	/*
+	 * Helper to show loaded overlays under: /proc/device-tree/chosen/overlays/
+	 */
+	fragment@0 {
+		target-path="/";
+		__overlay__ {
+
+			chosen {
+				overlays {
+					BB-SPI1-LTC2947-00A0 = __TIMESTAMP__;
+				};
+			};
+		};
+	};
+
+	/*
+	 * Free up the pins used by the cape from the pinmux helpers.
+	 */
+	fragment@1 {
+		target = <&ocp>;
+		__overlay__ {
+			P9_28_pinmux { status = "disabled"; };	/* spi1_cs0 */
+			P9_30_pinmux { status = "disabled"; };	/* spi1_d1 */
+			P9_29_pinmux { status = "disabled"; };	/* spi1_d0 */
+			P9_31_pinmux { status = "disabled"; };	/* spi1_sclk */
+		};
+	};
+
+	fragment@2 {
+		target = <&am33xx_pinmux>;
+		__overlay__ {
+			/* default state has all gpios released and mode set to uart1 */
+			bb_spi1_pins: pinmux_bb_spi1_pins {
+				pinctrl-single,pins = <
+					0x190 0x33	/* mcasp0_aclkx.spi1_sclk, INPUT_PULLUP | MODE3 */
+					0x194 0x33	/* mcasp0_fsx.spi1_d0, INPUT_PULLUP | MODE3 */
+					0x198 0x13	/* mcasp0_axr0.spi1_d1, OUTPUT_PULLUP | MODE3 */
+					0x19c 0x13	/* mcasp0_ahclkr.spi1_cs0, OUTPUT_PULLUP | MODE3 */
+				>;
+			};
+		};
+	};
+
+	fragment@3 {
+		target = <&spi1>;
+		__overlay__ {
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			status = "okay";
+			pinctrl-names = "default";
+			pinctrl-0 = <&bb_spi1_pins>;
+			ti,pio-mode; /* disable dma when used as an overlay, dma gets stuck at 160 bits... */
+
+			ltc2947_spi: ltc2947@0 {
+				#address-cells = <1>;
+				#size-cells = <0>;
+
+				compatible = "adi,ltc2947";
+
+				reg = <0>;
+				spi-max-frequency = <1000000>;
+			};
+		};
+	};
+};