clk: Stop forwarding clk_rate_requests to the parent

If the clock cannot modify its rate and has CLK_SET_RATE_PARENT,
clk_mux_determine_rate_flags(), clk_core_round_rate_nolock() and a
number of drivers will forward the clk_rate_request to the parent clock.

clk_core_round_rate_nolock() will pass the pointer directly, which means
that we pass a clk_rate_request to the parent that has the rate,
min_rate and max_rate of the child, and the best_parent_rate and
best_parent_hw fields will be relative to the child as well, so will
point to our current clock and its rate. The most common case for
CLK_SET_RATE_PARENT is that the child and parent clock rates will be
equal, so the rate field isn't a worry, but the other fields are.

Similarly, if the parent clock driver ever modifies the best_parent_rate
or best_parent_hw, this will be applied to the child once the call to
clk_core_round_rate_nolock() is done. best_parent_hw is probably not
going to be a valid parent, and best_parent_rate might lead to a parent
rate change different to the one that was initially computed.

clk_mux_determine_rate_flags() and the affected drivers will copy the
request before forwarding it to the parents, so they won't be affected
by the latter issue, but the former is still going to be there and will
lead to erroneous data and context being passed to the various clock
drivers in the same sub-tree.

Let's create two new functions, clk_core_forward_rate_req() and
clk_hw_forward_rate_request() for the framework and the clock providers
that will copy a request from a child clock and update the context to
match the parent's. We also update the relevant call sites in the
framework and drivers to use that new function.

Let's also add a test to make sure we avoid regressions there.

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/20220816112530.1837489-22-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>

1 files changed, 182 insertions, 0 deletions

diff --git a/drivers/clk/clk_test.c b/drivers/clk/clk_test.c
index 7068517428e2..3004ef368bd7 100644
--- a/drivers/clk/clk_test.c
+++ b/drivers/clk/clk_test.c
@@ -1026,6 +1026,36 @@ clk_test_single_parent_mux_set_range_disjoint_parent_last(struct kunit *test)
 
 /*
  * Test that for a clock that can't modify its rate and with a single
+ * parent, if we set a range on the parent and then call
+ * clk_round_rate(), the boundaries of the parent are taken into
+ * account.
+ */
+static void
+clk_test_single_parent_mux_set_range_round_rate_parent_only(struct kunit *test)
+{
+	struct clk_single_parent_ctx *ctx = test->priv;
+	struct clk_hw *hw = &ctx->hw;
+	struct clk *clk = clk_hw_get_clk(hw, NULL);
+	struct clk *parent;
+	unsigned long rate;
+	int ret;
+
+	parent = clk_get_parent(clk);
+	KUNIT_ASSERT_PTR_NE(test, parent, NULL);
+
+	ret = clk_set_rate_range(parent, DUMMY_CLOCK_RATE_1, DUMMY_CLOCK_RATE_2);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	rate = clk_round_rate(clk, DUMMY_CLOCK_RATE_1 - 1000);
+	KUNIT_ASSERT_GT(test, rate, 0);
+	KUNIT_EXPECT_GE(test, rate, DUMMY_CLOCK_RATE_1);
+	KUNIT_EXPECT_LE(test, rate, DUMMY_CLOCK_RATE_2);
+
+	clk_put(clk);
+}
+
+/*
+ * Test that for a clock that can't modify its rate and with a single
  * parent, if we set a range on the parent and a more restrictive one on
  * the child, and then call clk_round_rate(), the boundaries of the
  * two clocks are taken into account.
@@ -1062,12 +1092,52 @@ clk_test_single_parent_mux_set_range_round_rate_child_smaller(struct kunit *test
 	clk_put(clk);
 }
 
+/*
+ * Test that for a clock that can't modify its rate and with a single
+ * parent, if we set a range on the child and a more restrictive one on
+ * the parent, and then call clk_round_rate(), the boundaries of the
+ * two clocks are taken into account.
+ */
+static void
+clk_test_single_parent_mux_set_range_round_rate_parent_smaller(struct kunit *test)
+{
+	struct clk_single_parent_ctx *ctx = test->priv;
+	struct clk_hw *hw = &ctx->hw;
+	struct clk *clk = clk_hw_get_clk(hw, NULL);
+	struct clk *parent;
+	unsigned long rate;
+	int ret;
+
+	parent = clk_get_parent(clk);
+	KUNIT_ASSERT_PTR_NE(test, parent, NULL);
+
+	ret = clk_set_rate_range(parent, DUMMY_CLOCK_RATE_1 + 1000, DUMMY_CLOCK_RATE_2 - 1000);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	ret = clk_set_rate_range(clk, DUMMY_CLOCK_RATE_1, DUMMY_CLOCK_RATE_2);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	rate = clk_round_rate(clk, DUMMY_CLOCK_RATE_1 - 1000);
+	KUNIT_ASSERT_GT(test, rate, 0);
+	KUNIT_EXPECT_GE(test, rate, DUMMY_CLOCK_RATE_1 + 1000);
+	KUNIT_EXPECT_LE(test, rate, DUMMY_CLOCK_RATE_2 - 1000);
+
+	rate = clk_round_rate(clk, DUMMY_CLOCK_RATE_2 + 1000);
+	KUNIT_ASSERT_GT(test, rate, 0);
+	KUNIT_EXPECT_GE(test, rate, DUMMY_CLOCK_RATE_1 + 1000);
+	KUNIT_EXPECT_LE(test, rate, DUMMY_CLOCK_RATE_2 - 1000);
+
+	clk_put(clk);
+}
+
 static struct kunit_case clk_single_parent_mux_test_cases[] = {
 	KUNIT_CASE(clk_test_single_parent_mux_get_parent),
 	KUNIT_CASE(clk_test_single_parent_mux_has_parent),
 	KUNIT_CASE(clk_test_single_parent_mux_set_range_disjoint_child_last),
 	KUNIT_CASE(clk_test_single_parent_mux_set_range_disjoint_parent_last),
 	KUNIT_CASE(clk_test_single_parent_mux_set_range_round_rate_child_smaller),
+	KUNIT_CASE(clk_test_single_parent_mux_set_range_round_rate_parent_only),
+	KUNIT_CASE(clk_test_single_parent_mux_set_range_round_rate_parent_smaller),
 	{}
 };
 
@@ -2005,7 +2075,119 @@ static struct kunit_suite clk_range_minimize_test_suite = {
 	.test_cases = clk_range_minimize_test_cases,
 };
 
+struct clk_leaf_mux_ctx {
+	struct clk_multiple_parent_ctx mux_ctx;
+	struct clk_hw hw;
+};
+
+static int
+clk_leaf_mux_set_rate_parent_test_init(struct kunit *test)
+{
+	struct clk_leaf_mux_ctx *ctx;
+	const char *top_parents[2] = { "parent-0", "parent-1" };
+	int ret;
+
+	ctx = kunit_kzalloc(test, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+	test->priv = ctx;
+
+	ctx->mux_ctx.parents_ctx[0].hw.init = CLK_HW_INIT_NO_PARENT("parent-0",
+								    &clk_dummy_rate_ops,
+								    0);
+	ctx->mux_ctx.parents_ctx[0].rate = DUMMY_CLOCK_RATE_1;
+	ret = clk_hw_register(NULL, &ctx->mux_ctx.parents_ctx[0].hw);
+	if (ret)
+		return ret;
+
+	ctx->mux_ctx.parents_ctx[1].hw.init = CLK_HW_INIT_NO_PARENT("parent-1",
+								    &clk_dummy_rate_ops,
+								    0);
+	ctx->mux_ctx.parents_ctx[1].rate = DUMMY_CLOCK_RATE_2;
+	ret = clk_hw_register(NULL, &ctx->mux_ctx.parents_ctx[1].hw);
+	if (ret)
+		return ret;
+
+	ctx->mux_ctx.current_parent = 0;
+	ctx->mux_ctx.hw.init = CLK_HW_INIT_PARENTS("test-mux", top_parents,
+						   &clk_multiple_parents_mux_ops,
+						   0);
+	ret = clk_hw_register(NULL, &ctx->mux_ctx.hw);
+	if (ret)
+		return ret;
+
+	ctx->hw.init = CLK_HW_INIT_HW("test-clock", &ctx->mux_ctx.hw,
+				      &clk_dummy_single_parent_ops,
+				      CLK_SET_RATE_PARENT);
+	ret = clk_hw_register(NULL, &ctx->hw);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static void clk_leaf_mux_set_rate_parent_test_exit(struct kunit *test)
+{
+	struct clk_leaf_mux_ctx *ctx = test->priv;
+
+	clk_hw_unregister(&ctx->hw);
+	clk_hw_unregister(&ctx->mux_ctx.hw);
+	clk_hw_unregister(&ctx->mux_ctx.parents_ctx[0].hw);
+	clk_hw_unregister(&ctx->mux_ctx.parents_ctx[1].hw);
+}
+
+/*
+ * Test that, for a clock that will forward any rate request to its
+ * parent, the rate request structure returned by __clk_determine_rate
+ * is sane and will be what we expect.
+ */
+static void clk_leaf_mux_set_rate_parent_determine_rate(struct kunit *test)
+{
+	struct clk_leaf_mux_ctx *ctx = test->priv;
+	struct clk_hw *hw = &ctx->hw;
+	struct clk *clk = clk_hw_get_clk(hw, NULL);
+	struct clk_rate_request req;
+	unsigned long rate;
+	int ret;
+
+	rate = clk_get_rate(clk);
+	KUNIT_ASSERT_EQ(test, rate, DUMMY_CLOCK_RATE_1);
+
+	clk_hw_init_rate_request(hw, &req, DUMMY_CLOCK_RATE_2);
+
+	ret = __clk_determine_rate(hw, &req);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	KUNIT_EXPECT_EQ(test, req.rate, DUMMY_CLOCK_RATE_2);
+	KUNIT_EXPECT_EQ(test, req.best_parent_rate, DUMMY_CLOCK_RATE_2);
+	KUNIT_EXPECT_PTR_EQ(test, req.best_parent_hw, &ctx->mux_ctx.hw);
+
+	clk_put(clk);
+}
+
+static struct kunit_case clk_leaf_mux_set_rate_parent_test_cases[] = {
+	KUNIT_CASE(clk_leaf_mux_set_rate_parent_determine_rate),
+	{}
+};
+
+/*
+ * Test suite for a clock whose parent is a mux with multiple parents.
+ * The leaf clock has CLK_SET_RATE_PARENT, and will forward rate
+ * requests to the mux, which will then select which parent is the best
+ * fit for a given rate.
+ *
+ * These tests exercise the behaviour of muxes, and the proper selection
+ * of parents.
+ */
+static struct kunit_suite clk_leaf_mux_set_rate_parent_test_suite = {
+	.name = "clk-leaf-mux-set-rate-parent",
+	.init = clk_leaf_mux_set_rate_parent_test_init,
+	.exit = clk_leaf_mux_set_rate_parent_test_exit,
+	.test_cases = clk_leaf_mux_set_rate_parent_test_cases,
+};
+
 kunit_test_suites(
+	&clk_leaf_mux_set_rate_parent_test_suite,
 	&clk_test_suite,
 	&clk_multiple_parents_mux_test_suite,
 	&clk_orphan_transparent_multiple_parent_mux_test_suite,