[PATCH 19/22] clk: Stop forwarding clk_rate_requests to the parent

Maxime Ripard
2022-04-08T09:14:34Z

If the clock cannot modify its rate and has CLK_SET_RATE_PARENT,
clk_mux_determine_rate_flags() and clk_core_round_rate_nolock() will
call clk_core_round_rate_nolock() with its parent clock but use the
request of the child node either directly (clk_core_round_rate_nolock())
or by copying it (clk_mux_determine_rate_flags()).

Both cases are problematic since the parent will now have a request with
the best parent fields of the child (so pointing to itself) and the
boundaries of the child as well.

clk_core_round_rate_nolock() is even worse since we would directly
modify the caller structure if the parent was ever to modify its own
parent or its parent rate, then returning to the caller a best parent
that isn't a parent of the clock we just called clk_determine_rate()
onto.

Let's create a new function that will create a new request to forward to
the parent, clk_core_forward_rate_req() and update the relevant call
sites to that new function.

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

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
drivers/clk/clk.c | 58 ++++++++++++--
drivers/clk/clk_test.c | 176 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 227 insertions(+), 7 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 2bbeeb2f729e..53f5f7434be0 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -543,6 +543,10 @@ static bool mux_is_better_rate(unsigned long rate, unsigned long now,
return now <= rate && now > best;
}

+static void clk_core_init_rate_req(struct clk_core * const core,
+ struct clk_rate_request *req,
+ unsigned long rate);
+
static int clk_core_round_rate_nolock(struct clk_core *core,
struct clk_rate_request *req);

@@ -566,6 +570,24 @@ static bool clk_core_has_parent(struct clk_core *core, struct clk_core *parent)
return false;
}

+static void
+clk_core_forward_rate_req(struct clk_core * const core,
+ struct clk_core * const parent,
+ struct clk_rate_request * const old_req,
+ struct clk_rate_request *req)
+{
+ if (WARN_ON(!clk_core_has_parent(core, parent)))
+ return;
+
+ clk_core_init_rate_req(parent, req, old_req->rate);
+
+ if (req->min_rate < old_req->min_rate)
+ req->min_rate = old_req->min_rate;
+
+ if (req->max_rate > old_req->max_rate)
+ req->max_rate = old_req->max_rate;
+}
+
int clk_mux_determine_rate_flags(struct clk_hw *hw,
struct clk_rate_request *req,
unsigned long flags)
@@ -573,17 +595,19 @@ int clk_mux_determine_rate_flags(struct clk_hw *hw,
struct clk_core *core = hw->core, *parent, *best_parent = NULL;
int i, num_parents, ret;
unsigned long best = 0;
- struct clk_rate_request parent_req = *req;

/* if NO_REPARENT flag set, pass through to current parent */
if (core->flags & CLK_SET_RATE_NO_REPARENT) {
parent = core->parent;
if (core->flags & CLK_SET_RATE_PARENT) {
+ struct clk_rate_request parent_req;
+
if (!parent) {
req->rate = 0;
return 0;
}

+ clk_core_forward_rate_req(core, parent, req, &parent_req);
ret = clk_core_round_rate_nolock(parent, &parent_req);
if (ret)
return ret;
@@ -601,23 +625,29 @@ int clk_mux_determine_rate_flags(struct clk_hw *hw,
/* find the parent that can provide the fastest rate <= rate */
num_parents = core->num_parents;
for (i = 0; i < num_parents; i++) {
+ unsigned long parent_rate;
+
parent = clk_core_get_parent_by_index(core, i);
if (!parent)
continue;

if (core->flags & CLK_SET_RATE_PARENT) {
- parent_req = *req;
+ struct clk_rate_request parent_req;
+
+ clk_core_forward_rate_req(core, parent, req, &parent_req);
ret = clk_core_round_rate_nolock(parent, &parent_req);
if (ret)
continue;
+
+ parent_rate = parent_req.rate;
} else {
- parent_req.rate = clk_core_get_rate_nolock(parent);
+ parent_rate = clk_core_get_rate_nolock(parent);
}

- if (mux_is_better_rate(req->rate, parent_req.rate,
+ if (mux_is_better_rate(req->rate, parent_rate,
best, flags)) {
best_parent = parent;
- best = parent_req.rate;
+ best = parent_rate;
}
}

@@ -1451,6 +1481,8 @@ static bool clk_core_can_round(struct clk_core * const core)
static int clk_core_round_rate_nolock(struct clk_core *core,
struct clk_rate_request *req)
{
+ int ret;
+
lockdep_assert_held(&prepare_lock);

if (!core) {
@@ -1460,8 +1492,20 @@ static int clk_core_round_rate_nolock(struct clk_core *core,

if (clk_core_can_round(core))
return clk_core_determine_round_nolock(core, req);
- else if (core->flags & CLK_SET_RATE_PARENT)
- return clk_core_round_rate_nolock(core->parent, req);
+
+ if (core->flags & CLK_SET_RATE_PARENT) {
+ struct clk_rate_request parent_req;
+
+ clk_core_forward_rate_req(core, core->parent, req, &parent_req);
+ ret = clk_core_round_rate_nolock(core->parent, &parent_req);
+ if (ret)
+ return ret;
+
+ req->best_parent_rate = parent_req.rate;
+ req->rate = parent_req.rate;
+
+ return 0;
+ }

req->rate = core->rate;
return 0;
diff --git a/drivers/clk/clk_test.c b/drivers/clk/clk_test.c
index 0b9088cdb8fe..23e92f2d8445 100644
--- a/drivers/clk/clk_test.c
+++ b/drivers/clk/clk_test.c
@@ -997,6 +997,34 @@ clk_test_single_parent_mux_set_range_disjoint_parent_last(struct kunit *test)
KUNIT_EXPECT_LT(test, ret, 0);
}

+/*
+ * 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 = hw->clk;
+ 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);
+}
+
/*
* 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
@@ -1033,12 +1061,50 @@ clk_test_single_parent_mux_set_range_round_rate_child_smaller(struct kunit *test
KUNIT_EXPECT_LE(test, rate, DUMMY_CLOCK_RATE_2 - 1000);
}

+/*
+ * 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 = hw->clk;
+ 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);
+}
+
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),
{}
};

@@ -1945,7 +2011,117 @@ 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 = hw->clk;
+ 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);
+}
+
+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 are supposed to 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,
--
2.35.1