Problem: Some of our machines are configured with many NVMe devices and are validated for strict shutdown time requirements. Each NVMe device plugged into the system, typicaly takes about 4.5 secs to shutdown. A system with 16 such NVMe devices will takes approximately 80 secs to shutdown and go through reboot. The current shutdown APIs as defined at bus level is defined to be synchronous. Therefore, more devices are in the system the greater the time it takes to shutdown. This shutdown time significantly contributes the machine reboot time. Solution: This patch set proposes an asynchronous shutdown interface at bus level, modifies the core driver, device shutdown routine to exploit the new interface while maintaining backward compatibility with synchronous implementation already existing (Patch 1 of 3) and exploits new interface to enable all PCI-E based devices to use asynchronous interface semantics if necessary (Patch 2 of 3). The implementation at PCI-E level also works in a backward compatible way, to allow exiting device implementation to work with current synchronous semantics. Only show cases an example implementation for NVMe device to exploit this asynchronous shutdown interface. (Patch 3 of 3). Changelog: v2: - Replaced the shutdown_pre & shutdown_post entry point names with the recommended names (async_shutdown_start and asynch_shutdown_end). - Comment about ordering requirements between bridge shutdown versus leaf/endpoint shutdown was agreed to be different when calling async_shutdown_start and async_shutdown_end. Now this implements the same order of calling both start and end entry points. v3: - This notes clarifies why power management framework was not considered for implementing this shutdown optimization. There is no code change done. This change notes clarfies the reasoning only. This patch is only for shutdown of the system. The shutdown entry points are traditionally have different requirement where all devices are brought to a quiescent state and then system power may be removed (power down request scenarios) and also the same entry point is used to shutdown all devices and re-initialized and restarted (soft shutdown/reboot scenarios). Whereas, the device power management (dpm) allows the device to bring down any device configured in the system that may be idle to various low power states that the device may support in a selective manner and based on transitions that device implementation allows. The power state transitions initiated by the system can be achieved using 'dpm' interfaces already specified. Therefore the request to use the 'dpm' interface to achieve this shutdown optimization is not the right approach as the suggested interface is meant to solve an orthogonal requirement and have historically been kept separate from the shutdown entry points defined and its associated semantics. Tanjore Suresh (3): driver core: Support asynchronous driver shutdown PCI: Support asynchronous shutdown nvme: Add async shutdown support drivers/base/core.c | 38 +++++++++++++++++- drivers/nvme/host/core.c | 28 +++++++++---- drivers/nvme/host/nvme.h | 8 ++++ drivers/nvme/host/pci.c | 80 ++++++++++++++++++++++++-------------- drivers/pci/pci-driver.c | 20 ++++++++-- include/linux/device/bus.h | 12 ++++++ include/linux/pci.h | 4 ++ 7 files changed, 149 insertions(+), 41 deletions(-) -- 2.36.0.550.gb090851708-goog