On Thu, Jun 24, 2021 at 1:07 AM Vaibhav Jain <vaib...@linux.ibm.com> wrote: > > Persistent memory devices like NVDIMMs can loose cached writes in case > something prevents flush on power-fail. Such situations are termed as > dirty shutdown and are exposed to applications as > last-shutdown-state (LSS) flag and a dirty-shutdown-counter(DSC) as > described at [1]. The latter being useful in conditions where multiple > applications want to detect a dirty shutdown event without racing with > one another. > > PAPR-NVDIMMs have so far only exposed LSS style flags to indicate a > dirty-shutdown-state. This patch further adds support for DSC via the > "ibm,persistence-failed-count" device tree property of an NVDIMM. This > property is a monotonic increasing 64-bit counter thats an indication > of number of times an NVDIMM has encountered a dirty-shutdown event > causing persistence loss. > > Since this value is not expected to change after system-boot hence > papr_scm reads & caches its value during NVDIMM probe and exposes it > as a PAPR sysfs attributed named 'dirty_shutdown' to match the name of > similarly named NFIT sysfs attribute. Also this value is available to > libnvdimm via PAPR_PDSM_HEALTH payload. 'struct nd_papr_pdsm_health' > has been extended to add a new member called 'dimm_dsc' presence of > which is indicated by the newly introduced PDSM_DIMM_DSC_VALID flag. > > References: > [1] https://pmem.io/documents/Dirty_Shutdown_Handling-V1.0.pdf > > Signed-off-by: Vaibhav Jain <vaib...@linux.ibm.com> > Reviewed-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
Belated: Acked-by: Dan Williams <dan.j.willi...@intel.com> It's looking like CXL will add one of these as well. Might be time to add a unified location when that happens and deprecate these bus-specific locations.
