Rafael J. Wysocki 4eaefe8c62 nvme-pci: Allow PCI bus-level PM to be used if ASPM is disabled ... One of the modifications made by commit d916b1be94 ("nvme-pci: use host managed power state for suspend") was adding a pci_save_state() call to nvme_suspend() so as to instruct the PCI bus type to leave devices handled by the nvme driver in D0 during suspend-to-idle. That was done with the assumption that ASPM would transition the device's PCIe link into a low-power state when the device became inactive. However, if ASPM is disabled for the device, its PCIe link will stay in L0 and in that case commit d916b1be94 is likely to cause the energy used by the system while suspended to increase. Namely, if the device in question works in accordance with the PCIe specification, putting it into D3hot causes its PCIe link to go to L1 or L2/L3 Ready, which is lower-power than L0. Since the energy used by the system while suspended depends on the state of its PCIe link (as a general rule, the lower-power the state of the link, the less energy the system will use), putting the device into D3hot during suspend-to-idle should be more energy-efficient that leaving it in D0 with disabled ASPM. For this reason, avoid leaving NVMe devices with disabled ASPM in D0 during suspend-to-idle. Instead, shut them down entirely and let the PCI bus type put them into D3. Fixes: d916b1be94 ("nvme-pci: use host managed power state for suspend") Link: https://lore.kernel.org/linux-pm/2763495.NmdaWeg79L@kreacher/T/#t Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reviewed-by: Keith Busch <keith.busch@intel.com>		2019-08-12 10:47:55 +02:00
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host	nvme-pci: Allow PCI bus-level PM to be used if ASPM is disabled	2019-08-12 10:47:55 +02:00
target	for-linus-20190715	2019-07-15 21:20:52 -07:00
Kconfig	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
Makefile	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00