clk: Drop the rate range on clk_put()

When clk_put() is called we don't make another clk_set_rate() call to
re-evaluate the rate boundaries. This is unlike clk_set_rate_range()
that evaluates the rate again each time it is called.

However, clk_put() is essentially equivalent to clk_set_rate_range()
since after clk_put() completes the consumer's boundaries shouldn't be
enforced anymore.

Let's add a call to clk_set_rate_range() in clk_put() to make sure those
rate boundaries are dropped and the clock provider drivers can react. In
order to be as non-intrusive as possible, we'll just make that call if
the clock had non-default boundaries.

Also add a few tests to make sure this case is covered.

Fixes: c80ac50 ("clk: Always set the rate on clk_set_range_rate")
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/20220816112530.1837489-3-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.c

@@ -2325,19 +2325,15 @@ int clk_set_rate_exclusive(struct clk *clk, unsigned long rate)
 }
 EXPORT_SYMBOL_GPL(clk_set_rate_exclusive);
 
-/**
- * clk_set_rate_range - set a rate range for a clock source
- * @clk: clock source
- * @min: desired minimum clock rate in Hz, inclusive
- * @max: desired maximum clock rate in Hz, inclusive
- *
- * Returns success (0) or negative errno.
- */
-int clk_set_rate_range(struct clk *clk, unsigned long min, unsigned long max)
+static int clk_set_rate_range_nolock(struct clk *clk,
+				     unsigned long min,
+				     unsigned long max)
 {
 	int ret = 0;
 	unsigned long old_min, old_max, rate;
 
+	lockdep_assert_held(&prepare_lock);
+
 	if (!clk)
 		return 0;
 
@@ -2350,8 +2346,6 @@ int clk_set_rate_range(struct clk *clk, unsigned long min, unsigned long max)
 		return -EINVAL;
 	}
 
-	clk_prepare_lock();
-
 	if (clk->exclusive_count)
 		clk_core_rate_unprotect(clk->core);
 
@@ -2395,6 +2389,28 @@ int clk_set_rate_range(struct clk *clk, unsigned long min, unsigned long max)
 	if (clk->exclusive_count)
 		clk_core_rate_protect(clk->core);
 
+	return ret;
+}
+
+/**
+ * clk_set_rate_range - set a rate range for a clock source
+ * @clk: clock source
+ * @min: desired minimum clock rate in Hz, inclusive
+ * @max: desired maximum clock rate in Hz, inclusive
+ *
+ * Return: 0 for success or negative errno on failure.
+ */
+int clk_set_rate_range(struct clk *clk, unsigned long min, unsigned long max)
+{
+	int ret;
+
+	if (!clk)
+		return 0;
+
+	clk_prepare_lock();
+
+	ret = clk_set_rate_range_nolock(clk, min, max);
+
 	clk_prepare_unlock();
 
 	return ret;
@@ -4348,9 +4364,10 @@ void __clk_put(struct clk *clk)
 	}
 
 	hlist_del(&clk->clks_node);
-	if (clk->min_rate > clk->core->req_rate ||
-	    clk->max_rate < clk->core->req_rate)
-		clk_core_set_rate_nolock(clk->core, clk->core->req_rate);
+
+	/* If we had any boundaries on that clock, let's drop them. */
+	if (clk->min_rate > 0 || clk->max_rate < ULONG_MAX)
+		clk_set_rate_range_nolock(clk, 0, ULONG_MAX);
 
 	owner = clk->core->owner;
 	kref_put(&clk->core->ref, __clk_release);

drivers/clk/clk_test.c

@@ -793,9 +793,66 @@ static void clk_range_test_multiple_set_range_rate_maximized(struct kunit *test)
 	clk_put(clk);
 }
 
+/*
+ * Test that if we have several subsequent calls to
+ * clk_set_rate_range(), across multiple users, the core will reevaluate
+ * whether a new rate is needed, including when a user drop its clock.
+ *
+ * With clk_dummy_maximize_rate_ops, this means that the rate will
+ * trail along the maximum as it evolves.
+ */
+static void clk_range_test_multiple_set_range_rate_put_maximized(struct kunit *test)
+{
+	struct clk_dummy_context *ctx = test->priv;
+	struct clk_hw *hw = &ctx->hw;
+	struct clk *clk = clk_hw_get_clk(hw, NULL);
+	struct clk *user1, *user2;
+	unsigned long rate;
+
+	user1 = clk_hw_get_clk(hw, NULL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, user1);
+
+	user2 = clk_hw_get_clk(hw, NULL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, user2);
+
+	KUNIT_ASSERT_EQ(test,
+			clk_set_rate(clk, DUMMY_CLOCK_RATE_2 + 1000),
+			0);
+
+	KUNIT_ASSERT_EQ(test,
+			clk_set_rate_range(user1,
+					   0,
+					   DUMMY_CLOCK_RATE_2),
+			0);
+
+	rate = clk_get_rate(clk);
+	KUNIT_ASSERT_GT(test, rate, 0);
+	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_2);
+
+	KUNIT_ASSERT_EQ(test,
+			clk_set_rate_range(user2,
+					   0,
+					   DUMMY_CLOCK_RATE_1),
+			0);
+
+	rate = clk_get_rate(clk);
+	KUNIT_ASSERT_GT(test, rate, 0);
+	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_1);
+
+	clk_put(user2);
+
+	rate = clk_get_rate(clk);
+	KUNIT_ASSERT_GT(test, rate, 0);
+	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_2);
+
+	clk_put(user1);
+	clk_put(clk);
+}
+
 static struct kunit_case clk_range_maximize_test_cases[] = {
 	KUNIT_CASE(clk_range_test_set_range_rate_maximized),
 	KUNIT_CASE(clk_range_test_multiple_set_range_rate_maximized),
+	KUNIT_CASE(clk_range_test_multiple_set_range_rate_put_maximized),
 	{}
 };
 
@@ -913,9 +970,62 @@ static void clk_range_test_multiple_set_range_rate_minimized(struct kunit *test)
 	clk_put(clk);
 }
 
+/*
+ * Test that if we have several subsequent calls to
+ * clk_set_rate_range(), across multiple users, the core will reevaluate
+ * whether a new rate is needed, including when a user drop its clock.
+ *
+ * With clk_dummy_minimize_rate_ops, this means that the rate will
+ * trail along the minimum as it evolves.
+ */
+static void clk_range_test_multiple_set_range_rate_put_minimized(struct kunit *test)
+{
+	struct clk_dummy_context *ctx = test->priv;
+	struct clk_hw *hw = &ctx->hw;
+	struct clk *clk = clk_hw_get_clk(hw, NULL);
+	struct clk *user1, *user2;
+	unsigned long rate;
+
+	user1 = clk_hw_get_clk(hw, NULL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, user1);
+
+	user2 = clk_hw_get_clk(hw, NULL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, user2);
+
+	KUNIT_ASSERT_EQ(test,
+			clk_set_rate_range(user1,
+					   DUMMY_CLOCK_RATE_1,
+					   ULONG_MAX),
+			0);
+
+	rate = clk_get_rate(clk);
+	KUNIT_ASSERT_GT(test, rate, 0);
+	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_1);
+
+	KUNIT_ASSERT_EQ(test,
+			clk_set_rate_range(user2,
+					   DUMMY_CLOCK_RATE_2,
+					   ULONG_MAX),
+			0);
+
+	rate = clk_get_rate(clk);
+	KUNIT_ASSERT_GT(test, rate, 0);
+	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_2);
+
+	clk_put(user2);
+
+	rate = clk_get_rate(clk);
+	KUNIT_ASSERT_GT(test, rate, 0);
+	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_1);
+
+	clk_put(user1);
+	clk_put(clk);
+}
+
 static struct kunit_case clk_range_minimize_test_cases[] = {
 	KUNIT_CASE(clk_range_test_set_range_rate_minimized),
 	KUNIT_CASE(clk_range_test_multiple_set_range_rate_minimized),
+	KUNIT_CASE(clk_range_test_multiple_set_range_rate_put_minimized),
 	{}
 };