Commit 58a1fbbb2ee8 ("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 by querying the platform firmware and reading
its PMCSR.
Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
---
drivers/pci/pci-driver.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index e39a67c..fd4b9c4 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -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 */
--
2.8.1
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