clk: tests: Add test suites description

We start to have a few test suites, and we'll add more, so it will get
pretty confusing to figure out what is supposed to be tested in what
suite.

Let's add some comments to explain what setup they create, and what we
should be testing in every suite.

Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com> # imx8mp
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> # exynos4210, meson g12b
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220816112530.1837489-7-maxime@cerno.tech
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/clk_test.c

@@ -258,6 +258,11 @@ static struct kunit_case clk_test_cases[] = {
 	{}
 };
 
+/*
+ * Test suite for a basic rate clock, without any parent.
+ *
+ * These tests exercise the rate API with simple scenarios
+ */
 static struct kunit_suite clk_test_suite = {
 	.name = "clk-test",
 	.init = clk_test_init,
@@ -346,6 +351,14 @@ static struct kunit_case clk_orphan_transparent_single_parent_mux_test_cases[] =
 	{}
 };
 
+/*
+ * Test suite for a basic mux clock with one parent. The parent is
+ * registered after its child. The clock will thus be an orphan when
+ * registered, but will no longer be when the tests run.
+ *
+ * These tests make sure a clock that used to be orphan has a sane,
+ * consistent, behaviour.
+ */
 static struct kunit_suite clk_orphan_transparent_single_parent_test_suite = {
 	.name = "clk-orphan-transparent-single-parent-test",
 	.init = clk_orphan_transparent_single_parent_mux_test_init,
@@ -675,6 +688,12 @@ static struct kunit_case clk_range_test_cases[] = {
 	{}
 };
 
+/*
+ * Test suite for a basic rate clock, without any parent.
+ *
+ * These tests exercise the rate range API: clk_set_rate_range(),
+ * clk_set_min_rate(), clk_set_max_rate(), clk_drop_range().
+ */
 static struct kunit_suite clk_range_test_suite = {
 	.name = "clk-range-test",
 	.init = clk_test_init,
@@ -856,6 +875,13 @@ static struct kunit_case clk_range_maximize_test_cases[] = {
 	{}
 };
 
+/*
+ * Test suite for a basic rate clock, without any parent.
+ *
+ * These tests exercise the rate range API: clk_set_rate_range(),
+ * clk_set_min_rate(), clk_set_max_rate(), clk_drop_range(), with a
+ * driver that will always try to run at the highest possible rate.
+ */
 static struct kunit_suite clk_range_maximize_test_suite = {
 	.name = "clk-range-maximize-test",
 	.init = clk_maximize_test_init,
@@ -1029,6 +1055,13 @@ static struct kunit_case clk_range_minimize_test_cases[] = {
 	{}
 };
 
+/*
+ * Test suite for a basic rate clock, without any parent.
+ *
+ * These tests exercise the rate range API: clk_set_rate_range(),
+ * clk_set_min_rate(), clk_set_max_rate(), clk_drop_range(), with a
+ * driver that will always try to run at the lowest possible rate.
+ */
 static struct kunit_suite clk_range_minimize_test_suite = {
 	.name = "clk-range-minimize-test",
 	.init = clk_minimize_test_init,