linux-kernel - Re: [PATCH 1/5] clk: correct clk_div_mask() return value for width == 32

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Message-ID: <261F7D53235844E5+aNIOtLYG1NcypGqr@LT-Guozexi>
Date: Tue, 23 Sep 2025 11:06:28 +0800
From: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
To: Junhui Liu <junhui.liu@...moral.tech>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>
Cc: linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-riscv@...ts.infradead.org,
	"fushan.zeng" <fushan.zeng@...ogic.com>,
	Troy Mitchell <troy.mitchell@...ux.spacemit.com>
Subject: Re: [PATCH 1/5] clk: correct clk_div_mask() return value for width
 == 32

On Mon, Sep 22, 2025 at 10:51:47PM +0800, Junhui Liu wrote:
> The macro clk_div_mask() currently wraps to zero when width is 32 due to
> 1 << 32 being undefined behavior. This leads to incorrect mask generation
> and prevents correct retrieval of register field values for 32-bit-wide
> dividers.
> 
> Although it is unlikely to exhaust all U32_MAX div, some clock IPs may rely
> on a 32-bit val entry in their div_table to match a div, so providing a
> full 32-bit mask is necessary.
> 
> Fix this by casting 1 to long, ensuring proper behavior for valid widths up
> to 32.
> 
> Signed-off-by: Junhui Liu <junhui.liu@...moral.tech>
> ---
>  include/linux/clk-provider.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index 630705a47129453c241f1b1755f2c2f2a7ed8f77..a651ccaf1b44ff905c2bd4b9a7043f9e2169d27f 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -720,7 +720,7 @@ struct clk_divider {
>  	spinlock_t	*lock;
>  };
>  
> -#define clk_div_mask(width)	((1 << (width)) - 1)
> +#define clk_div_mask(width)	((1L << (width)) - 1)
Reviewed-by: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
>  #define to_clk_divider(_hw) container_of(_hw, struct clk_divider, hw)
>  
>  #define CLK_DIVIDER_ONE_BASED		BIT(0)
> 
> -- 
> 2.51.0
> 
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

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