linux-kernel - Re: [PATCH v2 1/1] i2c: designware: use u64 for clock freq to avoid u32 multiplication overflow

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Message-ID: <Y5n3hDsbbcnHaDHt@smile.fi.intel.com>
Date:   Wed, 14 Dec 2022 18:19:16 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Hanna Hawa <hhhawa@...zon.com>
Cc:     jarkko.nikula@...ux.intel.com, mika.westerberg@...ux.intel.com,
        jsd@...ihalf.com, 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@...zon.com
Subject: Re: [PATCH v2 1/1] i2c: designware: use u64 for clock freq to avoid
 u32 multiplication overflow

On Wed, Dec 14, 2022 at 06:18:07PM +0200, Andy Shevchenko wrote:
> On Wed, Dec 14, 2022 at 06:12:12PM +0200, Andy Shevchenko wrote:
> > On Wed, Dec 14, 2022 at 03:41:17PM +0000, Hanna Hawa wrote:
> > > From: Lareine Khawaly <lareine@...zon.com>
> > > 
> > > In functions i2c_dw_scl_lcnt() and i2c_dw_scl_hcnt() may have overflow
> > > by depending on the values of the given parameters including the ic_clk.
> > > For example in our use case where ic_clk is larger than one million,
> > > multiplication of ic_clk * 4700 will result in 32 bit overflow.
> > > 
> > > Make the ic_clk to be u64 parameter to avoid the overflow.
> > 
> > Below my comment, after addressing it,
> > Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> 
> Sorry, was too quick. I have to withdraw my tag since this patch obviously
> breaks a compilation for Intel Quark chip.

ld: drivers/i2c/busses/i2c-designware-common.o: in function `i2c_dw_scl_hcnt':
i2c-designware-common.c:(.text+0x5fe): undefined reference to `__udivdi3'
ld: i2c-designware-common.c:(.text+0x634): undefined reference to `__udivdi3'
ld: drivers/i2c/busses/i2c-designware-common.o: in function `i2c_dw_scl_lcnt':
i2c-designware-common.c:(.text+0x679): undefined reference to `__udivdi3'

> Please, test it carefully and submit new version when it will be ready.

-- 
With Best Regards,
Andy Shevchenko