linux-kernel - Re: [PATCH] dma: dmatest: Use div64

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Message-ID: <2023081654-dormitory-vocally-02f7@gregkh>
Date:   Wed, 16 Aug 2023 17:16:43 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     coolrrsh@...il.com
Cc:     vkoul@...nel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] dma: dmatest: Use div64_s64

On Wed, Aug 16, 2023 at 11:34:00AM +0530, coolrrsh@...il.com wrote:
> From: Rajeshwar R Shinde <coolrrsh@...il.com>
> 
> In the function do_div, the dividend is evaluated multiple times
> so it can cause side effects. Therefore replace it with div64_s64.
> 
> This fixes warning such as:
> drivers/dma/dmatest.c:496:1-7:
> WARNING: do_div() does a 64-by-32 division,
> please consider using div64_s64 instead.
> 
> Signed-off-by: Rajeshwar R Shinde <coolrrsh@...il.com>
> ---
>  drivers/dma/dmatest.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
> index ffe621695e47..07042f239db8 100644
> --- a/drivers/dma/dmatest.c
> +++ b/drivers/dma/dmatest.c
> @@ -9,6 +9,7 @@
>  
>  #include <linux/err.h>
>  #include <linux/delay.h>
> +#include <linux/math64.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/dmaengine.h>
>  #include <linux/freezer.h>
> @@ -493,7 +494,7 @@ static unsigned long long dmatest_persec(s64 runtime, unsigned int val)
>  
>  	per_sec *= val;
>  	per_sec = INT_TO_FIXPT(per_sec);
> -	do_div(per_sec, runtime);
> +	per_sec=div64_s64(per_sec, runtime);

Please always run checkpatch.pl on your changes before submitting them
for others to review.

thanks,

greg k-h