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Subject[PATCH v2 2/6] PCI / PM: Support for LEAVE_SUSPENDED driver flag
Date
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Add support for DPM_FLAG_LEAVE_SUSPENDED to the PCI bus type by
making it (a) set the power.may_skip_resume status bit for devices
that, from its perspective, may be left in suspend after system
wakeup from sleep and (b) return early from pci_pm_resume_noirq()
for devices whose remaining resume callbacks during the transition
under way are going to be skipped by the PM core.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
Documentation/power/pci.txt | 11 +++++++++++
drivers/pci/pci-driver.c | 19 +++++++++++++++++--
2 files changed, 28 insertions(+), 2 deletions(-)

Index: linux-pm/drivers/pci/pci-driver.c
===================================================================
--- linux-pm.orig/drivers/pci/pci-driver.c
+++ linux-pm/drivers/pci/pci-driver.c
@@ -699,7 +699,7 @@ static void pci_pm_complete(struct devic
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()) {
+ if (pm_runtime_suspended(dev) && pm_resume_via_firmware()) {
pci_power_t pre_sleep_state = pci_dev->current_state;

pci_update_current_state(pci_dev, pci_dev->current_state);
@@ -783,8 +783,10 @@ static int pci_pm_suspend_noirq(struct d
struct pci_dev *pci_dev = to_pci_dev(dev);
const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

- if (dev_pm_smart_suspend_and_suspended(dev))
+ if (dev_pm_smart_suspend_and_suspended(dev)) {
+ dev->power.may_skip_resume = true;
return 0;
+ }

if (pci_has_legacy_pm_support(pci_dev))
return pci_legacy_suspend_late(dev, PMSG_SUSPEND);
@@ -838,6 +840,16 @@ static int pci_pm_suspend_noirq(struct d
Fixup:
pci_fixup_device(pci_fixup_suspend_late, pci_dev);

+ /*
+ * If the target system sleep state is suspend-to-idle, it is sufficient
+ * to check whether or not the device's wakeup settings are good for
+ * runtime PM. Otherwise, the pm_resume_via_firmware() check will cause
+ * pci_pm_complete() to take care of fixing up the device's state
+ * anyway, if need be.
+ */
+ dev->power.may_skip_resume = device_may_wakeup(dev) ||
+ !device_can_wakeup(dev);
+
return 0;
}

@@ -847,6 +859,9 @@ static int pci_pm_resume_noirq(struct de
struct device_driver *drv = dev->driver;
int error = 0;

+ if (dev_pm_may_skip_resume(dev))
+ return 0;
+
/*
* Devices with DPM_FLAG_SMART_SUSPEND may be left in runtime suspend
* during system suspend, so update their runtime PM status to "active"
Index: linux-pm/Documentation/power/pci.txt
===================================================================
--- linux-pm.orig/Documentation/power/pci.txt
+++ linux-pm/Documentation/power/pci.txt
@@ -994,6 +994,17 @@ into D0 going forward), but if it is in
the function will set the power.direct_complete flag for it (to make the PM core
skip the subsequent "thaw" callbacks for it) and return.

+Setting the DPM_FLAG_LEAVE_SUSPENDED flag means that the driver prefers the
+device to be left in suspend after system-wide transitions to the working state.
+This flag is checked by the PM core, but the PCI bus type informs the PM core
+which devices may be left in suspend from its perspective (that happens during
+the "noirq" phase of system-wide suspend and analogous transitions) and next it
+uses the dev_pm_may_skip_resume() helper to decide whether or not to return from
+pci_pm_resume_noirq() early, as the PM core will skip the remaining resume
+callbacks for the device during the transition under way and will set its
+runtime PM status to "suspended" if dev_pm_may_skip_resume() returns "true" for
+it.
+
3.2. Device Runtime Power Management
------------------------------------
In addition to providing device power management callbacks PCI device drivers
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