From 48001ea50d17f3eb06a552e9ecf21f7fc01b25da Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Mon, 20 Jul 2020 15:08:18 -0700 Subject: PM, libnvdimm: Add runtime firmware activation support Abstract platform specific mechanics for nvdimm firmware activation behind a handful of generic ops. At the bus level ->activate_state() indicates the unified state (idle, busy, armed) of all DIMMs on the bus, and ->capability() indicates the system state expectations for activate. At the DIMM level ->activate_state() indicates the per-DIMM state, ->activate_result() indicates the outcome of the last activation attempt, and ->arm() attempts to transition the DIMM from 'idle' to 'armed'. A new hibernate_quiet_exec() facility is added to support firmware activation in an OS defined system quiesce state. It leverages the fact that the hibernate-freeze state wants to assert that a memory hibernation snapshot can be taken. This is in contrast to a platform firmware defined quiesce state that may forcefully quiet the memory controller independent of whether an individual device-driver properly supports hibernate-freeze. The libnvdimm sysfs interface is extended to support detection of a firmware activate capability. The mechanism supports enumeration and triggering of firmware activate, optionally in the hibernate_quiet_exec() context. [rafael: hibernate_quiet_exec() proposal] [vishal: fix up sparse warning, grammar in Documentation/] Cc: Pavel Machek Cc: Ira Weiny Cc: Len Brown Cc: Jonathan Corbet Cc: Dave Jiang Cc: Vishal Verma Reported-by: kernel test robot Co-developed-by: "Rafael J. Wysocki" Signed-off-by: "Rafael J. Wysocki" Signed-off-by: Dan Williams Signed-off-by: Vishal Verma --- .../driver-api/nvdimm/firmware-activate.rst | 86 ++++++++++++++++++++++ 1 file changed, 86 insertions(+) create mode 100644 Documentation/driver-api/nvdimm/firmware-activate.rst (limited to 'Documentation/driver-api') diff --git a/Documentation/driver-api/nvdimm/firmware-activate.rst b/Documentation/driver-api/nvdimm/firmware-activate.rst new file mode 100644 index 000000000000..7ee7decbbdc3 --- /dev/null +++ b/Documentation/driver-api/nvdimm/firmware-activate.rst @@ -0,0 +1,86 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================================== +NVDIMM Runtime Firmware Activation +================================== + +Some persistent memory devices run a firmware locally on the device / +"DIMM" to perform tasks like media management, capacity provisioning, +and health monitoring. The process of updating that firmware typically +involves a reboot because it has implications for in-flight memory +transactions. However, reboots are disruptive and at least the Intel +persistent memory platform implementation, described by the Intel ACPI +DSM specification [1], has added support for activating firmware at +runtime. + +A native sysfs interface is implemented in libnvdimm to allow platform +to advertise and control their local runtime firmware activation +capability. + +The libnvdimm bus object, ndbusX, implements an ndbusX/firmware/activate +attribute that shows the state of the firmware activation as one of 'idle', +'armed', 'overflow', and 'busy'. + +- idle: + No devices are set / armed to activate firmware + +- armed: + At least one device is armed + +- busy: + In the busy state armed devices are in the process of transitioning + back to idle and completing an activation cycle. + +- overflow: + If the platform has a concept of incremental work needed to perform + the activation it could be the case that too many DIMMs are armed for + activation. In that scenario the potential for firmware activation to + timeout is indicated by the 'overflow' state. + +The 'ndbusX/firmware/activate' property can be written with a value of +either 'live', or 'quiesce'. A value of 'quiesce' triggers the kernel to +run firmware activation from within the equivalent of the hibernation +'freeze' state where drivers and applications are notified to stop their +modifications of system memory. A value of 'live' attempts +firmware activation without this hibernation cycle. The +'ndbusX/firmware/activate' property will be elided completely if no +firmware activation capability is detected. + +Another property 'ndbusX/firmware/capability' indicates a value of +'live' or 'quiesce', where 'live' indicates that the firmware +does not require or inflict any quiesce period on the system to update +firmware. A capability value of 'quiesce' indicates that firmware does +expect and injects a quiet period for the memory controller, but 'live' +may still be written to 'ndbusX/firmware/activate' as an override to +assume the risk of racing firmware update with in-flight device and +application activity. The 'ndbusX/firmware/capability' property will be +elided completely if no firmware activation capability is detected. + +The libnvdimm memory-device / DIMM object, nmemX, implements +'nmemX/firmware/activate' and 'nmemX/firmware/result' attributes to +communicate the per-device firmware activation state. Similar to the +'ndbusX/firmware/activate' attribute, the 'nmemX/firmware/activate' +attribute indicates 'idle', 'armed', or 'busy'. The state transitions +from 'armed' to 'idle' when the system is prepared to activate firmware, +firmware staged + state set to armed, and 'ndbusX/firmware/activate' is +triggered. After that activation event the nmemX/firmware/result +attribute reflects the state of the last activation as one of: + +- none: + No runtime activation triggered since the last time the device was reset + +- success: + The last runtime activation completed successfully. + +- fail: + The last runtime activation failed for device-specific reasons. + +- not_staged: + The last runtime activation failed due to a sequencing error of the + firmware image not being staged. + +- need_reset: + Runtime firmware activation failed, but the firmware can still be + activated via the legacy method of power-cycling the system. + +[1]: https://docs.pmem.io/persistent-memory/ -- cgit v1.2.3