[PATCH v2 0/2] clk: fix corner case of clk_mux_determine_rate_flags()

[PATCH v2 0/2] clk: fix corner case of clk_mux_determine_rate_flags()

[Yang Xiwen via B4 Relay]

Signed-off-by: Yang Xiwen <forbidden405@outlook.com>
---
Changes in v2:
- Add a unit test to clk_test.c
- Link to v1: https://lore.kernel.org/r/20230421-clk-v1-1-bb503f2f2cf3@outlook.com

---
Yang Xiwen (2):
      clk: use ULONG_MAX as the initial value for the iteration in clk_mux_determine_rate_flags()
      clk: tests: Add missing test case for mux determine_rate

 drivers/clk/clk.c      | 5 ++++-
 drivers/clk/clk_test.c | 9 +++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)
---
base-commit: 76f598ba7d8e2bfb4855b5298caedd5af0c374a8
change-id: 20230421-clk-64c6b6e21cdb

Best regards,
-- 
Yang Xiwen <forbidden405@outlook.com>

[PATCH v2 1/2] clk: use ULONG_MAX as the initial value for the iteration in clk_mux_determine_rate_flags()

[Yang Xiwen via B4 Relay]

From: Yang Xiwen <forbidden405@outlook.com>

Currently, clk_mux_determine_rate_flags() use 0 as the initial value for
selecting the best matching parent. However, this will choose a
non-existant rate(0) if the requested rate is closer to 0 than the
minimum rate the parents have.

Fix that by initializing the initial value to ULONG_MAX and treat it as a
magic number.

Signed-off-by: Yang Xiwen <forbidden405@outlook.com>
---
 drivers/clk/clk.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index ae07685c7588b..ab8a2acfac8f3 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -541,6 +541,9 @@ EXPORT_SYMBOL_GPL(__clk_is_enabled);
 static bool mux_is_better_rate(unsigned long rate, unsigned long now,
 			   unsigned long best, unsigned long flags)
 {
+	if (best == ULONG_MAX)
+		return true;
+
 	if (flags & CLK_MUX_ROUND_CLOSEST)
 		return abs(now - rate) < abs(best - rate);
 
@@ -600,7 +603,7 @@ 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;
+	unsigned long best = ULONG_MAX;
 
 	/* if NO_REPARENT flag set, pass through to current parent */
 	if (core->flags & CLK_SET_RATE_NO_REPARENT) {

-- 
2.39.2

[PATCH v2 2/2] clk: tests: Add missing test case for mux determine_rate

[Yang Xiwen via B4 Relay]

From: Yang Xiwen <forbidden405@outlook.com>

Add a missing test case for determine_rate implemented by mux. It tests
the behavior of determine_rate when requesting a rate that none of the
parents could give.

Signed-off-by: Yang Xiwen <forbidden405@outlook.com>
---
 drivers/clk/clk_test.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/clk/clk_test.c b/drivers/clk/clk_test.c
index f9a5c2964c65d..9b1c90de90454 100644
--- a/drivers/clk/clk_test.c
+++ b/drivers/clk/clk_test.c
@@ -2215,6 +2215,15 @@ static void clk_leaf_mux_set_rate_parent_determine_rate(struct kunit *test)
 	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);
 
+	// Test a non-existant rate which none of the parents could give
+	clk_hw_init_rate_request(hw, &req, DUMMY_CLOCK_INIT_RATE);
+
+	ret = __clk_determine_rate(hw, &req);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	KUNIT_EXPECT_EQ(test, req.rate, DUMMY_CLOCK_RATE_1);
+	KUNIT_EXPECT_EQ(test, req.best_parent_rate, DUMMY_CLOCK_RATE_1);
+	KUNIT_EXPECT_PTR_EQ(test, req.best_parent_hw, &ctx->mux_ctx.hw);
 	clk_put(clk);
 }
 

-- 
2.39.2

Re: [PATCH v2 2/2] clk: tests: Add missing test case for mux determine_rate

[Stephen Boyd]

Quoting Yang Xiwen via B4 Relay (2023-04-25 00:46:40)
> From: Yang Xiwen <forbidden405@outlook.com>
> 
> Add a missing test case for determine_rate implemented by mux. It tests
> the behavior of determine_rate when requesting a rate that none of the
> parents could give.
> 
> Signed-off-by: Yang Xiwen <forbidden405@outlook.com>
> ---
>  drivers/clk/clk_test.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/clk/clk_test.c b/drivers/clk/clk_test.c
> index f9a5c2964c65d..9b1c90de90454 100644
> --- a/drivers/clk/clk_test.c
> +++ b/drivers/clk/clk_test.c
> @@ -2215,6 +2215,15 @@ static void clk_leaf_mux_set_rate_parent_determine_rate(struct kunit *test)
>         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);
>  
> +       // Test a non-existant rate which none of the parents could give
> +       clk_hw_init_rate_request(hw, &req, DUMMY_CLOCK_INIT_RATE);
> +
> +       ret = __clk_determine_rate(hw, &req);
> +       KUNIT_ASSERT_EQ(test, ret, 0);
> +
> +       KUNIT_EXPECT_EQ(test, req.rate, DUMMY_CLOCK_RATE_1);
> +       KUNIT_EXPECT_EQ(test, req.best_parent_rate, DUMMY_CLOCK_RATE_1);
> +       KUNIT_EXPECT_PTR_EQ(test, req.best_parent_hw, &ctx->mux_ctx.hw);

Please make an entire test case instead of modifying an existing test
case.