test/py: memtest: Add tests for mtest command

Add the following memory tests:
memtest_negative - To test mtest command by providing incorrect inputs
memtest_ddr - To test memory write-read-comparision for DDR memory

Signed-off-by: Love Kumar <love.kumar@amd.com>

test/py/tests/test_memtest.py

@@ -0,0 +1,68 @@
+# SPDX-License-Identifier: GPL-2.0
+# (C) Copyright 2023, Advanced Micro Devices, Inc.
+
+import pytest
+
+"""
+Note: This test relies on boardenv_* containing configuration values to define
+the memory test parameters such as start address, memory size, pattern,
+iterations and timeout. This test will be automatically skipped without this.
+
+For example:
+
+# Setup env__memtest to set the start address of the memory range, size of the
+# memory range to test from starting address, pattern to be written to memory,
+# number of test iterations, and expected time to complete the test of mtest
+# command. start address, size, and pattern parameters value should be in hex
+# and rest of the params value should be integer.
+env__memtest = {
+    'start_addr': 0x0,
+    'size': 0x1000,
+    'pattern': 0x0,
+    'iteration': 16,
+    'timeout': 50000,
+}
+"""
+
+def get_memtest_env(u_boot_console):
+    f = u_boot_console.config.env.get("env__memtest", None)
+    if not f:
+        pytest.skip("memtest is not enabled!")
+    else:
+        start = f.get("start_addr", 0x0)
+        size = f.get("size", 0x1000)
+        pattern = f.get("pattern", 0x0)
+        iteration = f.get("iteration", 2)
+        timeout = f.get("timeout", 50000)
+        end = hex(int(start) + int(size))
+        return start, end, pattern, iteration, timeout
+
+@pytest.mark.buildconfigspec("cmd_memtest")
+def test_memtest_negative(u_boot_console):
+    """Negative testcase where end address is smaller than starting address and
+    pattern is invalid."""
+    start, end, pattern, iteration, timeout = get_memtest_env(u_boot_console)
+    expected_response = "Refusing to do empty test"
+    response = u_boot_console.run_command(
+        f"mtest 2000 1000 {pattern} {hex(iteration)}"
+    )
+    assert expected_response in response
+    output = u_boot_console.run_command("echo $?")
+    assert not output.endswith("0")
+    u_boot_console.run_command(f"mtest {start} {end} 'xyz' {hex(iteration)}")
+    output = u_boot_console.run_command("echo $?")
+    assert not output.endswith("0")
+
+@pytest.mark.buildconfigspec("cmd_memtest")
+def test_memtest_ddr(u_boot_console):
+    """Test that md reads memory as expected, and that memory can be modified
+    using the mw command."""
+    start, end, pattern, iteration, timeout = get_memtest_env(u_boot_console)
+    expected_response = f"Tested {str(iteration)} iteration(s) with 0 errors."
+    with u_boot_console.temporary_timeout(timeout):
+        response = u_boot_console.run_command(
+            f"mtest {start} {end} {pattern} {hex(iteration)}"
+        )
+        assert expected_response in response
+    output = u_boot_console.run_command("echo $?")
+    assert output.endswith("0")