linux-kernel - Re: [PATCH v4 1/1] i2c: designware: use casting of u64 in clock multiplication to avoid overflow

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Message-ID: <Y6IMhZsbOk/J9xZB@smile.fi.intel.com>
Date:   Tue, 20 Dec 2022 21:27:01 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     "Hawa, Hanna" <hhhawa@...zon.com>
Cc:     wsa@...nel.org, jarkko.nikula@...ux.intel.com,
        mika.westerberg@...ux.intel.com, jsd@...ihalf.com,
        linus.walleij@...aro.org, ben-linux@...ff.org,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        dwmw@...zon.co.uk, benh@...zon.com, ronenk@...zon.com,
        talel@...zon.com, jonnyc@...zon.com, hanochu@...zon.com,
        farbere@...zon.com, itamark@...zon.com,
        Lareine Khawaly <lareine@...zon.com>
Subject: Re: [PATCH v4 1/1] i2c: designware: use casting of u64 in clock
 multiplication to avoid overflow

On Tue, Dec 20, 2022 at 09:23:53PM +0200, Andy Shevchenko wrote:
> On Tue, Dec 20, 2022 at 07:43:06PM +0200, Hawa, Hanna wrote:

...

> 		return DIV_ROUND_CLOSEST_ULL((u64)ic_clk * tSYMBOL, MICRO) -
> 		       8 + offset;
> 
> 		return DIV_ROUND_CLOSEST_ULL((u64)ic_clk * (tSYMBOL + tf), MICRO) -
> 		       3 + offset;
> 
> 	return DIV_ROUND_CLOSEST_ULL((u64)ic_clk * (tLOW + tf), MICRO) -
> 	       1 + offset;

Thinking more on this, I would probably replace the order of arguments to make
it ' + offset - N' in each case. Since plus will be on the previous line and
become first it will be easier to parse the arithmetical expression.

-- 
With Best Regards,
Andy Shevchenko