clk: Always clamp the rounded rate

The current core while setting the min and max rate properly in the
clk_request structure will not make sure that the requested rate is
within these boundaries, leaving it to each and every driver to make
sure it is.

It's not clear if this was on purpose or not, but this introduces some
inconsistencies within the API.

For example, a user setting a range and then calling clk_round_rate()
with a value outside of that range will get the same value back
(ignoring any driver adjustements), effectively ignoring the range that
was just set.

Another one, arguably worse, is that it also makes clk_round_rate() and
clk_set_rate() behave differently if there's a range and the rate being
used for both is outside that range. As we have seen, the rate will be
returned unchanged by clk_round_rate(), but clk_set_rate() will error
out returning -EINVAL.

Let's make sure the framework will always clamp the rate to the current
range found on the clock, which will fix both these inconsistencies.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220225143534.405820-5-maxime@cerno.tech
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/clk.c

@@ -1348,6 +1348,8 @@ static int clk_core_determine_round_nolock(struct clk_core *core,
 	if (!core)
 		return 0;
 
+	req->rate = clamp(req->rate, req->min_rate, req->max_rate);
+
 	/*
 	 * At this point, core protection will be disabled
 	 * - if the provider is not protected at all

drivers/clk/clk_test.c

@@ -310,8 +310,7 @@ static void clk_range_test_multiple_disjoints_range(struct kunit *test)
 
 /*
  * Test that if our clock has some boundaries and we try to round a rate
- * lower than the minimum, the returned rate won't be affected by the
- * boundaries.
+ * lower than the minimum, the returned rate will be within range.
  */
 static void clk_range_test_set_range_round_rate_lower(struct kunit *test)
 {
@@ -328,34 +327,42 @@ static void clk_range_test_set_range_round_rate_lower(struct kunit *test)
 
 	rate = clk_round_rate(clk, DUMMY_CLOCK_RATE_1 - 1000);
 	KUNIT_ASSERT_GT(test, rate, 0);
-	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_1 - 1000);
+	KUNIT_EXPECT_GE(test, rate, DUMMY_CLOCK_RATE_1);
+	KUNIT_EXPECT_LE(test, rate, DUMMY_CLOCK_RATE_2);
 }
 
 /*
  * Test that if our clock has some boundaries and we try to set a rate
- * lower than the minimum, we'll get an error.
+ * higher than the maximum, the new rate will be within range.
  */
 static void clk_range_test_set_range_set_rate_lower(struct kunit *test)
 {
 	struct clk_dummy_context *ctx = test->priv;
 	struct clk_hw *hw = &ctx->hw;
 	struct clk *clk = hw->clk;
+	unsigned long rate;
 
 	KUNIT_ASSERT_EQ(test,
 			clk_set_rate_range(clk,
 					   DUMMY_CLOCK_RATE_1,
 					   DUMMY_CLOCK_RATE_2),
 			0);
 
-	KUNIT_ASSERT_LT(test,
+	KUNIT_ASSERT_EQ(test,
 			clk_set_rate(clk, DUMMY_CLOCK_RATE_1 - 1000),
 			0);
+
+	rate = clk_get_rate(clk);
+	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 if our clock has some boundaries and we try to round and
- * set a rate lower than the minimum, the values won't be consistent
- * between clk_round_rate() and clk_set_rate().
+ * set a rate lower than the minimum, the rate returned by
+ * clk_round_rate() will be consistent with the new rate set by
+ * clk_set_rate().
  */
 static void clk_range_test_set_range_set_round_rate_consistent_lower(struct kunit *test)
 {
@@ -373,17 +380,16 @@ static void clk_range_test_set_range_set_round_rate_consistent_lower(struct kuni
 	rounded = clk_round_rate(clk, DUMMY_CLOCK_RATE_1 - 1000);
 	KUNIT_ASSERT_GT(test, rounded, 0);
 
-	KUNIT_EXPECT_LT(test,
+	KUNIT_ASSERT_EQ(test,
 			clk_set_rate(clk, DUMMY_CLOCK_RATE_1 - 1000),
 			0);
 
-	KUNIT_EXPECT_NE(test, rounded, clk_get_rate(clk));
+	KUNIT_EXPECT_EQ(test, rounded, clk_get_rate(clk));
 }
 
 /*
  * Test that if our clock has some boundaries and we try to round a rate
- * higher than the maximum, the returned rate won't be affected by the
- * boundaries.
+ * higher than the maximum, the returned rate will be within range.
  */
 static void clk_range_test_set_range_round_rate_higher(struct kunit *test)
 {
@@ -400,34 +406,42 @@ static void clk_range_test_set_range_round_rate_higher(struct kunit *test)
 
 	rate = clk_round_rate(clk, DUMMY_CLOCK_RATE_2 + 1000);
 	KUNIT_ASSERT_GT(test, rate, 0);
-	KUNIT_EXPECT_EQ(test, rate, DUMMY_CLOCK_RATE_2 + 1000);
+	KUNIT_EXPECT_GE(test, rate, DUMMY_CLOCK_RATE_1);
+	KUNIT_EXPECT_LE(test, rate, DUMMY_CLOCK_RATE_2);
 }
 
 /*
  * Test that if our clock has some boundaries and we try to set a rate
- * lower than the maximum, we'll get an error.
+ * higher than the maximum, the new rate will be within range.
  */
 static void clk_range_test_set_range_set_rate_higher(struct kunit *test)
 {
 	struct clk_dummy_context *ctx = test->priv;
 	struct clk_hw *hw = &ctx->hw;
 	struct clk *clk = hw->clk;
+	unsigned long rate;
 
 	KUNIT_ASSERT_EQ(test,
 			clk_set_rate_range(clk,
 					   DUMMY_CLOCK_RATE_1,
 					   DUMMY_CLOCK_RATE_2),
 			0);
 
-	KUNIT_ASSERT_LT(test,
+	KUNIT_ASSERT_EQ(test,
 			clk_set_rate(clk, DUMMY_CLOCK_RATE_2 + 1000),
 			0);
+
+	rate = clk_get_rate(clk);
+	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 if our clock has some boundaries and we try to round and
- * set a rate higher than the maximum, the values won't be consistent
- * between clk_round_rate() and clk_set_rate().
+ * set a rate higher than the maximum, the rate returned by
+ * clk_round_rate() will be consistent with the new rate set by
+ * clk_set_rate().
  */
 static void clk_range_test_set_range_set_round_rate_consistent_higher(struct kunit *test)
 {
@@ -445,11 +459,11 @@ static void clk_range_test_set_range_set_round_rate_consistent_higher(struct kun
 	rounded = clk_round_rate(clk, DUMMY_CLOCK_RATE_2 + 1000);
 	KUNIT_ASSERT_GT(test, rounded, 0);
 
-	KUNIT_EXPECT_LT(test,
+	KUNIT_ASSERT_EQ(test,
 			clk_set_rate(clk, DUMMY_CLOCK_RATE_2 + 1000),
 			0);
 
-	KUNIT_EXPECT_NE(test, rounded, clk_get_rate(clk));
+	KUNIT_EXPECT_EQ(test, rounded, clk_get_rate(clk));
 }
 
 /*