clk: Always set the rate on clk_set_range_rate

When we change a clock minimum or maximum using clk_set_rate_range(),
clk_set_min_rate() or clk_set_max_rate(), the current code will only
trigger a new rate change if the rate is outside of the new boundaries.

However, a clock driver might want to always keep the clock rate to
one of its boundary, for example the minimum to keep the power
consumption as low as possible.

Since they don't always get called though, clock providers don't have the
opportunity to implement this behaviour.

Let's trigger a clk_set_rate() on the previous requested rate every time
clk_set_rate_range() is called. That way, providers that care about the
new boundaries have a chance to adjust the rate, while providers that
don't care about those new boundaries will return the same rate than
before, which will be ignored by clk_set_rate() and won't result in a
new rate change.

Suggested-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220225143534.405820-7-maxime@cerno.tech
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

1 files changed, 24 insertions, 30 deletions

diff --git a/drivers/clk/clk_test.c b/drivers/clk/clk_test.c
index bc8d856f0ee8..8924a5ac56d8 100644
--- a/drivers/clk/clk_test.c
+++ b/drivers/clk/clk_test.c
@@ -549,13 +549,12 @@ static struct kunit_suite clk_range_test_suite = {
 };
 
 /*
- * Test that if:
- * - we have several subsequent calls to clk_set_rate_range();
- * - and we have a round_rate ops that always return the maximum
- *   frequency allowed;
+ * Test that if we have several subsequent calls to
+ * clk_set_rate_range(), the core will reevaluate whether a new rate is
+ * needed each and every time.
  *
- * The clock will run at the minimum of all maximum boundaries
- * requested, even if those boundaries aren't there anymore.
+ * With clk_dummy_maximize_rate_ops, this means that the rate will
+ * trail along the maximum as it evolves.
  */
 static void clk_range_test_set_range_rate_maximized(struct kunit *test)
 {
@@ -596,18 +595,16 @@ static void clk_range_test_set_range_rate_maximized(struct kunit *test)
 
 	rate = clk_get_rate(clk);
 	KUNIT_ASSERT_GT(test, rate, 0);
-	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_2 - 1000);
+	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_2);
 }
 
 /*
- * Test that if:
- * - we have several subsequent calls to clk_set_rate_range(), across
- *   multiple users;
- * - and we have a round_rate ops that always return the maximum
- *   frequency allowed;
+ * 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 each and every time.
  *
- * The clock will run at the minimum of all maximum boundaries
- * requested, even if those boundaries aren't there anymore.
+ * 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_maximized(struct kunit *test)
 {
@@ -653,7 +650,7 @@ static void clk_range_test_multiple_set_range_rate_maximized(struct kunit *test)
 
 	rate = clk_get_rate(clk);
 	KUNIT_ASSERT_GT(test, rate, 0);
-	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_1);
+	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_2);
 
 	clk_put(user2);
 	clk_put(user1);
@@ -673,13 +670,12 @@ static struct kunit_suite clk_range_maximize_test_suite = {
 };
 
 /*
- * Test that if:
- * - we have several subsequent calls to clk_set_rate_range()
- * - and we have a round_rate ops that always return the minimum
- *   frequency allowed;
+ * Test that if we have several subsequent calls to
+ * clk_set_rate_range(), the core will reevaluate whether a new rate is
+ * needed each and every time.
  *
- * The clock will run at the maximum of all minimum boundaries
- * requested, even if those boundaries aren't there anymore.
+ * With clk_dummy_minimize_rate_ops, this means that the rate will
+ * trail along the minimum as it evolves.
  */
 static void clk_range_test_set_range_rate_minimized(struct kunit *test)
 {
@@ -720,18 +716,16 @@ static void clk_range_test_set_range_rate_minimized(struct kunit *test)
 
 	rate = clk_get_rate(clk);
 	KUNIT_ASSERT_GT(test, rate, 0);
-	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_1 + 1000);
+	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_1);
 }
 
 /*
- * Test that if:
- * - we have several subsequent calls to clk_set_rate_range(), across
- *   multiple users;
- * - and we have a round_rate ops that always return the minimum
- *   frequency allowed;
+ * 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 each and every time.
  *
- * The clock will run at the maximum of all minimum boundaries
- * requested, even if those boundaries aren't there anymore.
+ * 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_minimized(struct kunit *test)
 {
@@ -773,7 +767,7 @@ static void clk_range_test_multiple_set_range_rate_minimized(struct kunit *test)
 
 	rate = clk_get_rate(clk);
 	KUNIT_ASSERT_GT(test, rate, 0);
-	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_2);
+	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_1);
 
 	clk_put(user2);
 	clk_put(user1);