[2/5] dmaengine: dmatest: Use fixed point div to calculate iops

[kbuild test robot <lkp@intel.com>]

Hi Seraj,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v4.18 next-20180824]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Seraj-Alijan/dmaengine-dmatest-Add-multi-chan-and-new-params/20180824-231828
config: i386-randconfig-n0-201833 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   drivers/dma/dmatest.o: In function `dmatest_persec':
>> drivers/dma/dmatest.c:457: undefined reference to `__udivdi3'
>> drivers/dma/dmatest.c:457: undefined reference to `__udivdi3'
>> drivers/dma/dmatest.c:457: undefined reference to `__udivdi3'

vim +457 drivers/dma/dmatest.c

   442	
   443	static unsigned long long dmatest_persec(s64 runtime, unsigned int val)
   444	{
   445		unsigned long long per_sec = 1000000;
   446	
   447		if (runtime <= 0)
   448			return 0;
   449	
   450		/* drop precision until runtime is 32-bits */
   451		while (runtime > UINT_MAX) {
   452			runtime >>= 1;
   453			per_sec <<= 1;
   454		}
   455	
   456		per_sec *= val;
 > 457		per_sec = FIXPT_DIV(per_sec, runtime);
   458	
   459		return per_sec;
   460	}
   461
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