[PATCH v2] clk: imx: pll14xx: Fix potential integer overflow

[PATCH v2] clk: imx: pll14xx: Fix potential integer overflow

[Stefan Ghetu]

From: Florin Pavelescu <florin.pavelescu@nxp.com>

Cast to u64, so that multiplications and additions will be done
in 64-bit arithmetic and the possibility of integer overflow is eliminated.

Fixes: 53990cf9d5b48 ("clk: imx: pll14xx: consolidate rate calculation")
Signed-off-by: Florin Pavelescu <florin.pavelescu@nxp.com>
Signed-off-by: Stefan Ghetu <stefan.ghetu@nxp.com>
---
Changes in v2:
- Drop the redundant (u64) cast on kdiv, as suggested by Frank Li.
  Adding a 32-bit value to a u64 already promotes it to u64.

 drivers/clk/imx/clk-pll14xx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/imx/clk-pll14xx.c b/drivers/clk/imx/clk-pll14xx.c
index c6438144e507..ee9a9e4c392a 100644
--- a/drivers/clk/imx/clk-pll14xx.c
+++ b/drivers/clk/imx/clk-pll14xx.c
@@ -124,7 +124,7 @@ static long pll14xx_calc_rate(struct clk_pll14xx *pll, int mdiv, int pdiv,
 	u64 fout = prate;
 
 	/* fout = (m * 65536 + k) * Fin / (p * 65536) / (1 << sdiv) */
-	fout *= (mdiv * 65536 + kdiv);
+	fout *= ((u64)mdiv * 65536 + kdiv);
 	pdiv *= 65536;
 
 	do_div(fout, pdiv << sdiv);
-- 
2.34.1

Re: [PATCH v2] clk: imx: pll14xx: Fix potential integer overflow

[Daniel Baluta]

On 11/9/26 13:31, Stefan Ghetu wrote:
> [You don't often get email from stefan.ghetu@nxp.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> From: Florin Pavelescu <florin.pavelescu@nxp.com>
> 
> Cast to u64, so that multiplications and additions will be done
> in 64-bit arithmetic and the possibility of integer overflow is eliminated.
> 
> Fixes: 53990cf9d5b48 ("clk: imx: pll14xx: consolidate rate calculation")
> Signed-off-by: Florin Pavelescu <florin.pavelescu@nxp.com>
> Signed-off-by: Stefan Ghetu <stefan.ghetu@nxp.com>

Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>

Re: [PATCH v2] clk: imx: pll14xx: Fix potential integer overflow

[Peng Fan]

On Mon, Nov 09, 2026 at 01:31:38PM +0200, Stefan Ghetu wrote:
>From: Florin Pavelescu <florin.pavelescu@nxp.com>
>
>Cast to u64, so that multiplications and additions will be done
>in 64-bit arithmetic and the possibility of integer overflow is eliminated.
>
>Fixes: 53990cf9d5b48 ("clk: imx: pll14xx: consolidate rate calculation")
>Signed-off-by: Florin Pavelescu <florin.pavelescu@nxp.com>
>Signed-off-by: Stefan Ghetu <stefan.ghetu@nxp.com>

It will not overflow. See this:
https://lore.kernel.org/all/6181060a-ae36-4d0f-bfe0-c1e5c8a8ab3c@gmail.com/

If we do want to silence some warnings from tools, drop the Fixes tag,
and update to commit message accordingly.

Regards
Peng