linux-kernel - Re: [PATCH v2] clk: hisilicon: Remove unnecessary local variable

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Message-ID: <bod2xxpj6xdutfiqq6zykcaxt3xyqor5qxiyi23g7oek3ndgpm@njl5h5ax5y2a>
Date: Thu, 1 Aug 2024 19:18:04 +0200
From: Uwe Kleine-König <u.kleine-koenig@...libre.com>
To: Thorsten Blum <thorsten.blum@...lux.com>
Cc: mturquette@...libre.com, sboyd@...nel.org, erick.archer@....com, 
	gustavoars@...nel.org, christophe.jaillet@...adoo.fr, linux-clk@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] clk: hisilicon: Remove unnecessary local variable

Hello,

On Thu, Aug 01, 2024 at 12:36:16PM +0200, Thorsten Blum wrote:
> The local u64 variable refdiv_val has the same value as the local u32
> variable val and can be removed. Remove it and use val directly as the
> divisor to also remove the following Coccinelle/coccicheck warning
> reported by do_div.cocci:
> 
>   WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead
> 
> Use the preferred div_u64() function instead of the do_div() macro.
> 
> Signed-off-by: Thorsten Blum <thorsten.blum@...lux.com>
> ---
> Changes in v2:
> - Use div_u64() instead of do_div() as suggested by Stephen Boyd
> - Link to v1: https://lore.kernel.org/linux-kernel/20240710201844.710365-2-thorsten.blum@toblux.com/
> ---
>  drivers/clk/hisilicon/clk-hi3559a.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/clk/hisilicon/clk-hi3559a.c b/drivers/clk/hisilicon/clk-hi3559a.c
> index c79a94f6d9d2..8646e9d352ed 100644
> --- a/drivers/clk/hisilicon/clk-hi3559a.c
> +++ b/drivers/clk/hisilicon/clk-hi3559a.c
> @@ -407,7 +407,7 @@ static unsigned long clk_pll_recalc_rate(struct clk_hw *hw,
>  		unsigned long parent_rate)
>  {
>  	struct hi3559av100_clk_pll *clk = to_pll_clk(hw);
> -	u64 frac_val, fbdiv_val, refdiv_val;
> +	u64 frac_val, fbdiv_val;
>  	u32 postdiv1_val, postdiv2_val;
>  	u32 val;
>  	u64 tmp, rate;
> @@ -435,14 +435,13 @@ static unsigned long clk_pll_recalc_rate(struct clk_hw *hw,
>  	val = readl_relaxed(clk->ctrl_reg2);
>  	val = val >> clk->refdiv_shift;
>  	val &= ((1 << clk->refdiv_width) - 1);
> -	refdiv_val = val;
>  
>  	/* rate = 24000000 * (fbdiv + frac / (1<<24) ) / refdiv  */
>  	rate = 0;
>  	tmp = 24000000 * fbdiv_val + (24000000 * frac_val) / (1 << 24);
>  	rate += tmp;
> -	do_div(rate, refdiv_val);
> -	do_div(rate, postdiv1_val * postdiv2_val);
> +	rate = div_u64(rate, val);
> +	rate = div_u64(rate, postdiv1_val * postdiv2_val);

Without looking at the bigger context: Can postdiv1_val * postdiv2_val
overflow? (If this is a problem, fixing it justifies another patch, so
this concern shouldn't stop this patch from being accepted.)

Otherwise looks fine,
Acked-by: Uwe Kleine-König <u.kleine-koenig@...libre.com>

Best regards
Uwe

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