1d4dd7091SDan WilliamsWhat: /sys/bus/nd/devices/regionX/nfit/ecc_unit_size 2d4dd7091SDan WilliamsDate: Aug, 2017 3d4dd7091SDan WilliamsKernelVersion: v4.14 (Removed v4.18) 4*3dd4fe4bSDan WilliamsContact: nvdimm@lists.linux.dev 5d4dd7091SDan WilliamsDescription: 6d4dd7091SDan Williams (RO) Size of a write request to a DIMM that will not incur a 7d4dd7091SDan Williams read-modify-write cycle at the memory controller. 8d4dd7091SDan Williams 9d4dd7091SDan Williams When the nfit driver initializes it runs an ARS (Address Range 10d4dd7091SDan Williams Scrub) operation across every pmem range. Part of that process 11d4dd7091SDan Williams involves determining the ARS capabilities of a given address 12d4dd7091SDan Williams range. One of the capabilities that is reported is the 'Clear 13d4dd7091SDan Williams Uncorrectable Error Range Length Unit Size' (see: ACPI 6.2 14d4dd7091SDan Williams section 9.20.7.4 Function Index 1 - Query ARS Capabilities). 15d4dd7091SDan Williams This property indicates the boundary at which the NVDIMM may 16d4dd7091SDan Williams need to perform read-modify-write cycles to maintain ECC (Error 17d4dd7091SDan Williams Correcting Code) blocks. 18