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PCI: Activate runtime PM on a PCIe port only if it can suspend

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Currently pcie_portdrv_probe() activates runtime PM on a PCIe port even
if it will never actually suspend because the BIOS is too old or the
"pcie_port_pm=off" option was specified on the kernel command line.

A few CPU cycles can be saved by not activating runtime PM at all in these
cases, because rpm_idle() and rpm_suspend() will bail out right at the
beginning when calling rpm_check_suspend_allowed(), instead of carrying out
various locking and assignments, invoking rpm_callback(), getting back
-EBUSY and rolling everything back.

The conditions checked in pci_bridge_d3_possible() are all static, they
never change during uptime of the system, hence it's safe to call this to
determine if runtime PM should be activated.

No functional change intended.

Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Lukas Wunner 2016-10-28 10:52:06 +02:00 committed by Bjorn Helgaas
parent e8559b7100
commit c6a6330706
3 changed files with 5 additions and 3 deletions
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2
drivers/pci/pci.c
View File

@ -2230,7 +2230,7 @@ void pci_config_pm_runtime_put(struct pci_dev *pdev)
* This function checks if it is possible to move the bridge to D3.
* Currently we only allow D3 for recent enough PCIe ports.
*/
static bool pci_bridge_d3_possible(struct pci_dev *bridge)
bool pci_bridge_d3_possible(struct pci_dev *bridge)
{
unsigned int year;

1
drivers/pci/pci.h
View File

@ -85,6 +85,7 @@ void pci_pm_init(struct pci_dev *dev);
void pci_ea_init(struct pci_dev *dev);
void pci_allocate_cap_save_buffers(struct pci_dev *dev);
void pci_free_cap_save_buffers(struct pci_dev *dev);
bool pci_bridge_d3_possible(struct pci_dev *dev);
void pci_bridge_d3_update(struct pci_dev *dev);
static inline void pci_wakeup_event(struct pci_dev *dev)

5
drivers/pci/pcie/portdrv_pci.c
View File

@ -19,6 +19,7 @@
#include <linux/dmi.h>
#include <linux/pci-aspm.h>
#include "../pci.h"
#include "portdrv.h"
#include "aer/aerdrv.h"
@ -157,7 +158,7 @@ static int pcie_portdrv_probe(struct pci_dev *dev,
* subordinate devices). We can't be sure for native PCIe hotplug
* either so prevent that as well.
*/
if (!dev->is_hotplug_bridge) {
if (pci_bridge_d3_possible(dev) && !dev->is_hotplug_bridge) {
/*
* Keep the port resumed 100ms to make sure things like
* config space accesses from userspace (lspci) will not
@ -175,7 +176,7 @@ static int pcie_portdrv_probe(struct pci_dev *dev,
static void pcie_portdrv_remove(struct pci_dev *dev)
{
if (!dev->is_hotplug_bridge) {
if (pci_bridge_d3_possible(dev) && !dev->is_hotplug_bridge) {
pm_runtime_forbid(&dev->dev);
pm_runtime_get_noresume(&dev->dev);
pm_runtime_dont_use_autosuspend(&dev->dev);