Commit a0d2a959 authored Sep 18, 2016 by Lukas Wunner Committed by Bjorn Helgaas Sep 28, 2016

PCI: Avoid unnecessary resume after direct-complete



Commit 58a1fbbb ("PM / PCI / ACPI: Kick devices that might have been
reset by firmware") added a runtime resume for devices that were runtime
suspended when the system entered sleep.

The motivation was that devices might be in a reset-power-on state after
waking from system sleep, so their power state as perceived by Linux
(stored in pci_dev->current_state) would no longer reflect reality.  By
resuming such devices, we allow them to return to a low-power state via
autosuspend and also bring their current_state in sync with reality.

However for devices that are *not* in a reset-power-on state, doing an
unconditional resume wastes energy.  A more refined approach is called for
which issues a runtime resume only if the power state after direct-complete
is shallower than it was before. To achieve this, update the device's
current_state and compare it to its pre-sleep value.

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent a6a64026

drivers/pci/pci-driver.c

+13 −2

Original line number	Diff line number	Diff line
		@@ -684,8 +684,19 @@ static int pci_pm_prepare(struct device *dev)

		static void pci_pm_complete(struct device *dev)
		{
		pci_dev_complete_resume(to_pci_dev(dev));
		pm_complete_with_resume_check(dev);
		struct pci_dev *pci_dev = to_pci_dev(dev);

		pci_dev_complete_resume(pci_dev);
		pm_generic_complete(dev);

		/* Resume device if platform firmware has put it in reset-power-on */
		if (dev->power.direct_complete && pm_resume_via_firmware()) {
		pci_power_t pre_sleep_state = pci_dev->current_state;

		pci_update_current_state(pci_dev, pci_dev->current_state);
		if (pci_dev->current_state < pre_sleep_state)
		pm_request_resume(dev);
		}
		}

		#else /* !CONFIG_PM_SLEEP */

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