tests: drivers: pwm: add PWM loopback test

Add test cases for the PWM capture API using PWM signal loopback.

Signed-off-by: Henrik Brix Andersen <hebad@vestas.com>

tests/drivers/pwm/pwm_loopback/CMakeLists.txt

@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.13.1)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(pwm_loopback)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

tests/drivers/pwm/pwm_loopback/boards/frdm_k64f.overlay

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+/*
+ * Copyright (c) 2020-2021 Vestas Wind Systems A/S
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <dt-bindings/pwm/pwm.h>
+
+/ {
+	pwm_loopback_0 {
+		compatible = "test,pwm_loopback";
+		pwms = <&ftm0 0 0 PWM_POLARITY_NORMAL>, /* PTC1, J1 pin 5 */
+		       <&ftm3 4 0 PWM_POLARITY_NORMAL>; /* PTC8, J1 pin 7 */
+	};
+};

tests/drivers/pwm/pwm_loopback/dts/bindings/test,pwm_loopback.yaml

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+#
+# Copyright (c) 2020-2021 Vestas Wind Systems A/S
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+description: |
+    This binding provides resources required to build and run the
+    tests/drivers/pwm/pwm_loopback test in Zephyr.
+
+compatible: "test,pwm_loopback"
+
+properties:
+    pwms:
+        type: phandle-array
+        required: true
+        description: |
+          PWM pins that will be used for generating and capturing a pulse-width
+          modulated signal. The pin at the first index will be used for signal
+          generation while the pin at the second index will be used for capuring
+          the generated signal. The two pins must be physically connected to
+          each other.

tests/drivers/pwm/pwm_loopback/prj.conf

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+CONFIG_ZTEST=y
+CONFIG_TEST_USERSPACE=y
+
+CONFIG_PWM=y
+CONFIG_PWM_CAPTURE=y

tests/drivers/pwm/pwm_loopback/src/main.c

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+/*
+ * Copyright (c) 2020-2021 Vestas Wind Systems A/S
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr.h>
+#include <ztest.h>
+
+#include "test_pwm_loopback.h"
+
+void test_main(void)
+{
+	struct test_pwm in;
+	struct test_pwm out;
+
+	get_test_pwms(&in, &out);
+
+	k_object_access_grant(out.dev, k_current_get());
+	k_object_access_grant(in.dev, k_current_get());
+
+	ztest_test_suite(pwm_loopback_test,
+			 ztest_user_unit_test(test_pulse_capture),
+			 ztest_user_unit_test(test_pulse_capture_inverted),
+			 ztest_user_unit_test(test_period_capture),
+			 ztest_user_unit_test(test_period_capture_inverted),
+			 ztest_user_unit_test(test_pulse_and_period_capture),
+			 ztest_user_unit_test(test_capture_timeout),
+			 ztest_unit_test(test_continuous_capture),
+			 ztest_unit_test(test_capture_busy));
+	ztest_run_test_suite(pwm_loopback_test);
+}