linux-kernel - Re: [PATCH] regulator: pwm: Try to avoid voltage error in duty cycle calculation

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Date:	Fri, 1 Apr 2016 12:02:19 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	kbuild test robot <lkp@...el.com>
CC:	<kbuild-all@...org>, <broonie@...nel.org>, <lgirdwood@...il.com>,
	<linux-kernel@...r.kernel.org>, Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH] regulator: pwm: Try to avoid voltage error in duty cycle
 calculation


On Friday 01 April 2016 11:55 AM, kbuild test robot wrote:
> Hi Laxman,
>
> [auto build test ERROR on regulator/for-next]
> [also build test ERROR on v4.6-rc1 next-20160401]
> [if your patch is applied to the wrong git tree, please drop us a note to help improving the system]
>
> url:    https://github.com/0day-ci/linux/commits/Laxman-Dewangan/regulator-pwm-Try-to-avoid-voltage-error-in-duty-cycle-calculation/20160331-220703
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator.git for-next
> config: i386-randconfig-a0-04010940 (attached as .config)
> reproduce:
>          # save the attached .config to linux build tree
>          make ARCH=i386
>
> All errors (new ones prefixed by >>):
>
>     drivers/built-in.o: In function `pwm_regulator_set_voltage':
>>> pwm-regulator.c:(.text+0x1728d4): undefined reference to `__umoddi3'
>>> pwm-regulator.c:(.text+0x1728fd): undefined reference to `__udivdi3'
>


Seems build error is coming from logic

u64 req_period
unsigned int diff;
unsigned int period
unsigned int req_diff


req_period = req_diff * period;
if (req_period % diff == 0)


used u64 to avoid overflow in multiplication.