Hi "Aneesh,

I love your patch! Yet something to improve:

[auto build test ERROR on powerpc/next]
[also build test ERROR on linux-nvdimm/libnvdimm-for-next v5.8-rc3 next-20200629]
[cannot apply to scottwood/next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use  as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Aneesh-Kumar-K-V/Support-new-pmem-flush-and-sync-instructions-for-POWER/20200629-223649
base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: arc-allyesconfig (attached as .config)
compiler: arc-elf-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        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
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=arc 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>

All errors (new ones prefixed by >>):

   drivers/nvdimm/region_devs.c: In function 'generic_nvdimm_flush':

quoted

drivers/nvdimm/region_devs.c:1215:2: error: implicit declaration of function 'arch_pmem_flush_barrier' [-Werror=implicit-function-declaration]

    1215 |  arch_pmem_flush_barrier();
         |  ^~~~~~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors

vim +/arch_pmem_flush_barrier +1215 drivers/nvdimm/region_devs.c

  1178	
  1179	int nvdimm_flush(struct nd_region *nd_region, struct bio *bio)
  1180	{
  1181		int rc = 0;
  1182	
  1183		if (!nd_region->flush)
  1184			rc = generic_nvdimm_flush(nd_region);
  1185		else {
  1186			if (nd_region->flush(nd_region, bio))
  1187				rc = -EIO;
  1188		}
  1189	
  1190		return rc;
  1191	}
  1192	/**
  1193	 * nvdimm_flush - flush any posted write queues between the cpu and pmem media
  1194	 * @nd_region: blk or interleaved pmem region
  1195	 */
  1196	int generic_nvdimm_flush(struct nd_region *nd_region)
  1197	{
  1198		struct nd_region_data *ndrd = dev_get_drvdata(&nd_region->dev);
  1199		int i, idx;
  1200	
  1201		/*
  1202		 * Try to encourage some diversity in flush hint addresses
  1203		 * across cpus assuming a limited number of flush hints.
  1204		 */
  1205		idx = this_cpu_read(flush_idx);
  1206		idx = this_cpu_add_return(flush_idx, hash_32(current->pid + idx, 8));
  1207	
  1208		/*
  1209		 * The first arch_pmem_flush_barrier() is needed to 'sfence' all
  1210		 * previous writes such that they are architecturally visible for
  1211		 * the platform buffer flush. Note that we've already arranged for pmem
  1212		 * writes to avoid the cache via memcpy_flushcache().  The final
  1213		 * wmb() ensures ordering for the NVDIMM flush write.
  1214		 */

1215		arch_pmem_flush_barrier();

  1216		for (i = 0; i < nd_region->ndr_mappings; i++)
  1217			if (ndrd_get_flush_wpq(ndrd, i, 0))
  1218				writeq(1, ndrd_get_flush_wpq(ndrd, i, idx));
  1219		wmb();
  1220	
  1221		return 0;
  1222	}
  1223	EXPORT_SYMBOL_GPL(nvdimm_flush);
  1224	

---
0-DAY CI Kernel Test Service, Intel Corporation
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