Commit c6a63307 authored by Lukas Wunner's avatar Lukas Wunner Committed by Bjorn Helgaas
Browse files

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



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: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: default avatarLukas Wunner <lukas@wunner.de>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent e8559b71

drivers/pci/pci.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

drivers/pci/pci.h

+1 −0
Original line number Diff line number Diff line
@@ -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)

drivers/pci/pcie/portdrv_pci.c

+3 −2
Original line number Diff line number Diff line
@@ -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);

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