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PCI: Avoid unnecessary resume after direct-complete

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Commit 58a1fbbb2e ("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>
This commit is contained in:
Lukas Wunner 2016-09-18 05:39:20 +02:00 committed by Bjorn Helgaas
parent a6a64026c0
commit a0d2a959d3
1 changed files with 13 additions and 2 deletions
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15
drivers/pci/pci-driver.c
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@ -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 */