Thread (3 messages) 3 messages, 2 authors, 2025-09-18

Re: [PATCH] clk: tegra: super: Fix error handling and resolve unsigned compare warning

From: Mikko Perttunen <mperttunen@nvidia.com>
Date: 2025-09-18 01:55:14
Also in: linux-tegra, lkml

On Friday, August 29, 2025 10:16 AM Pei Xiao wrote:
quoted hunk ↗ jump to hunk
./drivers/clk/tegra/clk-super.c:156:5-9: WARNING:
        Unsigned expression compared with zero: rate < 0

The unsigned long 'rate' variable caused:
- Incorrect handling of negative errors
- Compile warning: "Unsigned expression compared with zero"

Fix by changing to long type and adding req->rate cast.

Signed-off-by: Pei Xiao <redacted>
---
 drivers/clk/tegra/clk-super.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/clk/tegra/clk-super.c b/drivers/clk/tegra/clk-super.c
index 7ec47942720c..643b3cb83cd0 100644
--- a/drivers/clk/tegra/clk-super.c
+++ b/drivers/clk/tegra/clk-super.c
@@ -147,7 +147,7 @@ static int clk_super_determine_rate(struct clk_hw *hw,
 {
 	struct tegra_clk_super_mux *super = to_clk_super_mux(hw);
 	struct clk_hw *div_hw = &super->frac_div.hw;
-	unsigned long rate;
+	long rate;
 
 	__clk_hw_set_clk(div_hw, hw);
 
@@ -156,7 +156,7 @@ static int clk_super_determine_rate(struct clk_hw *hw,
 	if (rate < 0)
 		return rate;
 
-	req->rate = rate;
+	req->rate = (unsigned long)rate;
 	return 0;
 }
 
The proper fix for this would be to implement and call div_ops->determine_rate instead of round_rate. With the cast-to-long approach, rates above 2147MHz will incorrectly show as errors. While for this clock in particular I don't think we can reach those rates, I don't think this improves the situation either, as the round_rate implementation invoked here never returns errors.

Mikko

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