samples: reserved_memory: Introduce sample application

Introduce sample application to test reserved-memory helpers.

Signed-off-by: Carlo Caione <ccaione@baylibre.com>

samples/boards/qemu_cortex_a53/reserved_memory/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.13.1)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(reserved_memory)
+
+target_sources(app PRIVATE src/main.c)

samples/boards/qemu_cortex_a53/reserved_memory/boards/qemu_cortex_a53.overlay

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+/*
+ * Copyright (c) 2021 Carlo Caione <ccaione@baylibre.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	reserved-memory {
+		compatible = "reserved-memory";
+		#address-cells = <1>;
+		#size-cells = <1>;
+		status = "okay";
+		ranges;
+
+		res0: res0@42000000 {
+			reg = <0x42000000 0x1000>;
+			label = "res0";
+		};
+
+		res1: res1@43000000 {
+			reg = <0x43000000 0x2000>;
+			compatible = "sample_driver";
+			label = "res1";
+		};
+	};
+
+
+	sample_driver_outer: sample_driver {
+		compatible = "sample_driver";
+		label = "sample_driver_outer";
+		memory-region = <&res0>;
+	};
+};

samples/boards/qemu_cortex_a53/reserved_memory/dts/bindings/sample_driver.yaml

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+description: Sample Driver
+
+compatible: "sample_driver"
+
+include:
+  - name: base.yaml
+    property-allowlist: ['reg', 'label']
+
+properties:
+    memory-region:
+      type: phandle
+      required: false
+      description: phandle to the reserved memory child node

samples/boards/qemu_cortex_a53/reserved_memory/linker_arm64_reserved.ld

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+/*
+ * Copyright (c) Carlo Caione <ccaione@baylibre.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <autoconf.h>
+#include <linker/sections.h>
+#include <devicetree.h>
+
+#include <linker/linker-defs.h>
+#include <linker/linker-tool.h>
+
+MEMORY
+{
+    DT_RESERVED_MEM_REGIONS()
+}
+
+SECTIONS
+{
+    DT_RESERVED_MEM_SECTIONS()
+}
+
+#include <arch/arm64/scripts/linker.ld>

samples/boards/qemu_cortex_a53/reserved_memory/prj.conf

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+CONFIG_HAVE_CUSTOM_LINKER_SCRIPT=y
+CONFIG_CUSTOM_LINKER_SCRIPT="linker_arm64_reserved.ld"

samples/boards/qemu_cortex_a53/reserved_memory/sample.yaml

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+sample:
+  description: Reserved memory sample application
+  name: reserved memory
+tests:
+  sample.board.qemu_cortex_a53.reserved_memory:
+    platform_allow: qemu_cortex_a53
+    tags: sample board reserved_memory
+    build_only: true

samples/boards/qemu_cortex_a53/reserved_memory/src/main.c

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+/*
+ * Copyright (c) 2021 Carlo Caione <ccaione@baylibre.com>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr.h>
+#include <devicetree/memory.h>
+#include <linker/linker-defs.h>
+
+/* Variables placed in reserved sections */
+uint32_t var_in_res0 __attribute((__section__(".res0"))) = 0xaabbccdd;
+uint32_t var_in_res1 __attribute((__section__(".res1"))) = 0xddccbbaa;
+
+void main(void)
+{
+	uint8_t *res_ptr_outer, *res_ptr_inner;
+	uint32_t res_size_outer, res_size_inner;
+
+	res_ptr_outer =
+		DT_RESERVED_MEM_GET_PTR_BY_PHANDLE(DT_NODELABEL(sample_driver_outer),
+						   memory_region);
+	res_size_outer =
+		DT_RESERVED_MEM_GET_SIZE_BY_PHANDLE(DT_NODELABEL(sample_driver_outer),
+						    memory_region);
+
+	printk("Reserved memory address for the outer driver: %p\n", res_ptr_outer);
+	printk("Reserved memory size for the outer driver: %d\n", res_size_outer);
+
+	res_ptr_inner = DT_RESERVED_MEM_GET_PTR(DT_NODELABEL(res1));
+	res_size_inner = DT_RESERVED_MEM_GET_SIZE(DT_NODELABEL(res1));
+
+	printk("Reserved memory address for the inner driver: %p\n", res_ptr_inner);
+	printk("Reserved memory size for the inner driver: %d\n", res_size_inner);
+
+	printk("Address of var_in_res0: %p\n", &var_in_res0);
+	printk("Address of var_in_res1: %p\n", &var_in_res1);
+}