Hi Zhenzhong,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on pm/linux-next]
[cannot apply to v5.4-rc2 next-20191011]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Zhenzhong-Duan/cpuidle-cpu-hotplug-support/20191014-000932
base:   https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git linux-next
config: mips-allmodconfig (attached as .config)
compiler: mips-linux-gcc (GCC) 7.4.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.4.0 make.cross ARCH=mips 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/cpuidle/cpuidle.c: In function 'cpuidle_cpu_online':
>> drivers/cpuidle/cpuidle.c:580:6: error: 'coupled_cpus' undeclared (first use in this function); did you mean 'total_cpus'?
     if (coupled_cpus)
         ^~~~~~~~~~~~
         total_cpus
   drivers/cpuidle/cpuidle.c:580:6: note: each undeclared identifier is reported only once for each function it appears in

vim +580 drivers/cpuidle/cpuidle.c

   560	
   561	static int cpuidle_cpu_online(unsigned int cpu)
   562	{
   563		int ret;
   564		struct cpuidle_device *device;
   565		struct cpuidle_driver *drv;
   566	
   567		device = &per_cpu(cpuidle_dev, cpu);
   568		device->cpu = cpu;
   569	
   570		drv = cpuidle_get_cpu_driver(device);
   571		if (!drv || !cpumask_test_cpu(cpu, drv->cpumask))
   572			return 0;
   573	
   574	#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
   575		/*
   576		 * On multiplatform for ARM, the coupled idle states could be
   577		 * enabled in the kernel even if the cpuidle driver does not
   578		 * use it. Note, coupled_cpus is a struct copy.
   579		 */
 > 580		if (coupled_cpus)
   581			device->coupled_cpus = *coupled_cpus;
   582	#endif
   583		ret = cpuidle_register_device(device);
   584		if (ret)
   585			pr_err("Failed to register cpuidle device for cpu%d\n", cpu);
   586	
   587		return ret;
   588	}
   589	

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