include: riscv: add RISC-V arch atomic instructions

Add RISC-V architecture specific atomic instructions, not present in
atomic_builtin.h

Signed-off-by: Aleksandar Cecaric <aleksandar.cecaric@nextsilicon.com>

tests/arch/riscv/atomic/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(riscv_atomic)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

tests/arch/riscv/atomic/prj.conf

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+CONFIG_ZTEST=y
+CONFIG_MP_MAX_NUM_CPUS=1

tests/arch/riscv/atomic/src/main.c

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+/*
+ * Copyright (c) 2024 NextSilicon LTD
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/ztest.h>
+#include <zephyr/sys/atomic.h>
+#include <zephyr/arch/riscv/atomic.h>
+
+/**
+ * @brief Verify RISC-V specific atomic functionalities
+ * @details
+ * Test Objective:
+ * - Test if the RISC-V atomic instructions API is correct.
+ *
+ * Test Procedure:
+ * - Call the API interface of the following atomic operations in turn,
+ * decision is based on function return value and target operands.
+ * - atomic_swap()
+ * - atomic_max()
+ * - atomic_min()
+ *
+ * Expected Test Result:
+ * - The function return value and target operands are correct.
+ *
+ * Pass/Fail Criteria:
+ * - Successful if all check points in the test procedure have passed, failure otherwise.
+ */
+
+#define ATOMIC_WORD(val_if_64, val_if_32)                                                          \
+	((atomic_t)((sizeof(void *) == sizeof(uint64_t)) ? (val_if_64) : (val_if_32)))
+
+ZTEST_USER(riscv_atomic, test_atomic)
+{
+	atomic_t target;
+	atomic_val_t value;
+	unsigned long utarget, uvalue;
+
+	zassert_equal(sizeof(atomic_t), ATOMIC_WORD(sizeof(uint64_t), sizeof(uint32_t)),
+		      "sizeof(atomic_t)");
+
+	/* atomic_swap */
+	target = 21;
+	value = 7;
+	zassert_true((atomic_swap(&target, value) == 21), "atomic_swap");
+	zassert_true((target == 7), "atomic_swap");
+
+	/* atomic_max */
+	target = 5;
+	value = -8;
+	zassert_true((atomic_max(&target, value) == 5), "atomic_max");
+	zassert_true((target == 5), "atomic_max");
+
+	/* atomic_min */
+	target = 5;
+	value = -8;
+	zassert_true((atomic_min(&target, value) == 5), "atomic_min");
+	zassert_true((target == -8), "atomic_min");
+
+	/* atomic_max unsigned */
+	utarget = 5;
+	uvalue = ATOMIC_WORD(0xffffffff00000000, 0xffff0000);
+	zassert_true((atomic_maxu(&utarget, uvalue) == 5), "atomic_maxu");
+	zassert_true((utarget == ATOMIC_WORD(0xffffffff00000000, 0xffff0000)), "atomic_maxu");
+
+	/* atomic_min unsigned */
+	utarget = 5;
+	uvalue = ATOMIC_WORD(0xffffffff00000000, 0xffff0000);
+	zassert_true((atomic_minu(&utarget, uvalue) == 5), "atomic_minu");
+	zassert_true((utarget == 5), "atomic_minu");
+}
+
+ZTEST_SUITE(riscv_atomic, NULL, NULL, NULL, NULL, NULL);

tests/arch/riscv/atomic/testcase.yaml

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+tests:
+  arch.riscv.atomic:
+    arch_allow: riscv
+    filter: CONFIG_RISCV_ISA_EXT_A and not CONFIG_SOC_OPENISA_RV32M1