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

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Message-ID: <5700F966.4000802@nvidia.com>
Date:	Sun, 3 Apr 2016 16:37:18 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	Mark Brown <broonie@...nel.org>
CC:	kbuild test robot <lkp@...el.com>, <kbuild-all@...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 Saturday 02 April 2016 10:23 PM, Mark Brown wrote:
> * PGP Signed by an unknown key
>
> On Fri, Apr 01, 2016 at 12:02:19PM +0530, Laxman Dewangan wrote:
>> On Friday 01 April 2016 11:55 AM, kbuild test robot wrote:
>>>>> 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.
> Yes, you're doing a 64 bit divide so that's kind of expected...
>

Is there any way to resolve this issue?

Otherwise, need to divide by 100 first for the req_diff to get 10x of mV 
(instead of uV) and then do calculation with unsigned int only. That way 
I can restrict the number to unsigned int.