Initial unit test for SFDP

As a starting point, only sfdp_iterate_next_largest_erase_type(),
which the pull request is intended to fix, is tested. More test
cases shall be added in the future.

drivers/tests/UNITTESTS/SFDP/test_sfdp.cpp

@@ -0,0 +1,101 @@
+/* Copyright (c) 2020 ARM Limited
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "gtest/gtest.h"
+#include "gmock/gmock.h"
+#include "drivers/internal/SFDP.h"
+
+class TestSFDP : public testing::Test {
+protected:
+    struct mbed::sfdp_smptbl_info smptbl;
+
+    /**
+     * Construct Mbed OS SFDP info.
+     * Normally this is parsed from the flash-chips's
+     * raw SFDP table bytes, but for unit test we construct
+     * SFDP info manually
+     */
+    virtual void SetUp()
+    {
+        // The mock flash supports 4KB, 32KB and 64KB erase types
+        smptbl.erase_type_size_arr[0] = 4 * 1024;
+        smptbl.erase_type_size_arr[1] = 32 * 1024;
+        smptbl.erase_type_size_arr[2] = 64 * 1024;
+
+        // The mock flash has three regions, with address ranges:
+        // * 0 to 64KB - 1B
+        // * 64KB to 256KB - 1B
+        // * 256KB to 1024KB - 1B
+        smptbl.region_high_boundary[0] = 64 * 1024 - 1;
+        smptbl.region_high_boundary[1] = 256 * 1024 - 1;
+        smptbl.region_high_boundary[2] = 1024 * 1024 - 1;
+
+        // Bitfields indicating which regions support which erase types
+        smptbl.region_erase_types_bitfld[0] = 0b0001;   // 4KB only
+        smptbl.region_erase_types_bitfld[1] = 0b0111;   // 64KB, 32KB, 4KB
+        smptbl.region_erase_types_bitfld[2] = 0b0110;   // 64KB, 32KB
+    }
+};
+
+/**
+ * Test if sfdp_iterate_next_largest_erase_type() returns the most
+ * optimal erase type, whose erase size is as large as possible
+ * while being compatible with both alignment and size requirements.
+ */
+TEST_F(TestSFDP, TestEraseTypeAlgorithm)
+{
+    // Erase 104KB starting at 92KB
+    int address = 92 * 1024;
+    int size = 104 * 1024;
+    int region = 1;
+    int type;
+
+    // Expected outcome:
+    // * The starting position 92KB is 4KB-aligned
+    // * The next position 96KB (92KB + 4KB) is 32KB-aligned
+    // * The next position 128KB (96KB + 32KB) is 64KB-aligned
+    // * At the final position 192KB (128KB + 64KB), we only
+    //   have 4KB (104KB - 4KB - 32KB - 64KB) remaining to erase
+    int expected_erase_KBs[] = {4, 32, 64, 4};
+
+    for (int i = 0; i < sizeof(expected_erase_KBs) / sizeof(int); i++) {
+        type = sfdp_iterate_next_largest_erase_type(
+                    smptbl.region_erase_types_bitfld[region],
+                    size,
+                    address,
+                    region,
+                    smptbl);
+        int erase_size = smptbl.erase_type_size_arr[type];
+        EXPECT_EQ(erase_size, expected_erase_KBs[i] * 1024);
+        address += erase_size;
+        size -= erase_size;
+    }
+
+    EXPECT_EQ(size, 0); // All erased
+
+    // Test unaligned erase
+    // Region 2 only allows at least 32KB-aligned erases
+    address = (512 + 16) * 1024;
+    size = 64 * 1024;
+    region = 2;
+    type = sfdp_iterate_next_largest_erase_type(
+                smptbl.region_erase_types_bitfld[region],
+                size,
+                address,
+                region,
+                smptbl);
+    EXPECT_EQ(type, -1); // Invalid erase
+}

drivers/tests/UNITTESTS/SFDP/unittest.cmake

@@ -0,0 +1,20 @@
+
+####################
+# UNIT TESTS
+####################
+set(TEST_SUITE_NAME "SFDP")
+
+# Source files
+set(unittest-sources
+  ../drivers/source/SFDP.cpp
+)
+
+# Test files
+set(unittest-test-sources
+  ../drivers/tests/UNITTESTS/SFDP/test_sfdp.cpp
+  stubs/mbed_assert_stub.cpp
+)
+
+set(unittest-test-flags
+  -DDEVICE_SPI
+)