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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-10-25 14:12:29 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-11-06 13:55:30 +0100
commit08810a4119aaebf6318f209ec5dd9828e969cba4 (patch)
tree9ee6db2759e7005c5a2bdc3e1b1c33cf11d9dd12 /Documentation/power
parent69a10ca747c2d2d7c0354a883335e097c067ed35 (diff)
PM / core: Add NEVER_SKIP and SMART_PREPARE driver flags
The motivation for this change is to provide a way to work around a problem with the direct-complete mechanism used for avoiding system suspend/resume handling for devices in runtime suspend. The problem is that some middle layer code (the PCI bus type and the ACPI PM domain in particular) returns positive values from its system suspend ->prepare callbacks regardless of whether the driver's ->prepare returns a positive value or 0, which effectively prevents drivers from being able to control the direct-complete feature. Some drivers need that control, however, and the PCI bus type has grown its own flag to deal with this issue, but since it is not limited to PCI, it is better to address it by adding driver flags at the core level. To that end, add a driver_flags field to struct dev_pm_info for flags that can be set by device drivers at the probe time to inform the PM core and/or bus types, PM domains and so on on the capabilities and/or preferences of device drivers. Also add two static inline helpers for setting that field and testing it against a given set of flags and make the driver core clear it automatically on driver remove and probe failures. Define and document two PM driver flags related to the direct- complete feature: NEVER_SKIP and SMART_PREPARE that can be used, respectively, to indicate to the PM core that the direct-complete mechanism should never be used for the device and to inform the middle layer code (bus types, PM domains etc) that it can only request the PM core to use the direct-complete mechanism for the device (by returning a positive value from its ->prepare callback) if it also has been requested by the driver. While at it, make the core check pm_runtime_suspended() when setting power.direct_complete so that it doesn't need to be checked by ->prepare callbacks. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Diffstat (limited to 'Documentation/power')
-rw-r--r--Documentation/power/pci.txt19
1 files changed, 19 insertions, 0 deletions
diff --git a/Documentation/power/pci.txt b/Documentation/power/pci.txt
index a1b7f7158930..ab4e7d0540c1 100644
--- a/Documentation/power/pci.txt
+++ b/Documentation/power/pci.txt
@@ -961,6 +961,25 @@ dev_pm_ops to indicate that one suspend routine is to be pointed to by the
.suspend(), .freeze(), and .poweroff() members and one resume routine is to
be pointed to by the .resume(), .thaw(), and .restore() members.
+3.1.19. Driver Flags for Power Management
+
+The PM core allows device drivers to set flags that influence the handling of
+power management for the devices by the core itself and by middle layer code
+including the PCI bus type. The flags should be set once at the driver probe
+time with the help of the dev_pm_set_driver_flags() function and they should not
+be updated directly afterwards.
+
+The DPM_FLAG_NEVER_SKIP flag prevents the PM core from using the direct-complete
+mechanism allowing device suspend/resume callbacks to be skipped if the device
+is in runtime suspend when the system suspend starts. That also affects all of
+the ancestors of the device, so this flag should only be used if absolutely
+necessary.
+
+The DPM_FLAG_SMART_PREPARE flag instructs the PCI bus type to only return a
+positive value from pci_pm_prepare() if the ->prepare callback provided by the
+driver of the device returns a positive value. That allows the driver to opt
+out from using the direct-complete mechanism dynamically.
+
3.2. Device Runtime Power Management
------------------------------------
In addition to providing device power management callbacks PCI device drivers