linux-kernel - Re: [PATCH v5 08/15] clk: at91: clk-master: check if div or pres is zero

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Date:   Fri, 15 Oct 2021 09:55:35 +0200
From:   Nicolas Ferre <nicolas.ferre@...rochip.com>
To:     Claudiu Beznea <claudiu.beznea@...rochip.com>,
        <mturquette@...libre.com>, <sboyd@...nel.org>,
        <alexandre.belloni@...tlin.com>, <ludovic.desroches@...rochip.com>
CC:     <linux-clk@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 08/15] clk: at91: clk-master: check if div or pres is
 zero

On 11/10/2021 at 13:27, Claudiu Beznea wrote:
> Check if div or pres is zero before using it as argument for ffs().
> In case div is zero ffs() will return 0 and thus substracting from
> zero will lead to invalid values to be setup in registers.
> 
> Fixes: 7a110b9107ed8 ("clk: at91: clk-master: re-factor master clock")
> Fixes: 75c88143f3b87 ("clk: at91: clk-master: add master clock support for SAMA7G5")
> Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>

Acked-by: Nicolas Ferre <nicolas.ferre@...rochip.com>

> ---
>   drivers/clk/at91/clk-master.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/at91/clk-master.c b/drivers/clk/at91/clk-master.c
> index 9a2c8e64cacf..2093e13b5068 100644
> --- a/drivers/clk/at91/clk-master.c
> +++ b/drivers/clk/at91/clk-master.c
> @@ -344,7 +344,7 @@ static int clk_master_pres_set_rate(struct clk_hw *hw, unsigned long rate,
>   
>   	else if (pres == 3)
>   		pres = MASTER_PRES_MAX;
> -	else
> +	else if (pres)
>   		pres = ffs(pres) - 1;
>   
>   	spin_lock_irqsave(master->lock, flags);
> @@ -757,7 +757,7 @@ static int clk_sama7g5_master_set_rate(struct clk_hw *hw, unsigned long rate,
>   
>   	if (div == 3)
>   		div = MASTER_PRES_MAX;
> -	else
> +	else if (div)
>   		div = ffs(div) - 1;
>   
>   	spin_lock_irqsave(master->lock, flags);
> 


-- 
Nicolas Ferre