7d715a6c1a
PCI Express ASPM defines a protocol for PCI Express components in the D0
state to reduce Link power by placing their Links into a low power state
and instructing the other end of the Link to do likewise. This
capability allows hardware-autonomous, dynamic Link power reduction
beyond what is achievable by software-only controlled power management.
However, The device should be configured by software appropriately.
Enabling ASPM will save power, but will introduce device latency.
This patch adds ASPM support in Linux. It introduces a global policy for
ASPM, a sysfs file /sys/module/pcie_aspm/parameters/policy can control
it. The interface can be used as a boot option too. Currently we have
below setting:
-default, BIOS default setting
-powersave, highest power saving mode, enable all available ASPM
state and clock power management
-performance, highest performance, disable ASPM and clock power
management
By default, the 'default' policy is used currently.
In my test, power difference between powersave mode and performance mode
is about 1.3w in a system with 3 PCIE links.
Note: some devices might not work well with aspm, either because chipset
issue or device issue. The patch provide API (pci_disable_link_state),
driver can disable ASPM for specific device.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
155 lines
3.5 KiB
C
155 lines
3.5 KiB
C
#include <linux/pci.h>
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#include <linux/module.h>
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#include <linux/pci-aspm.h>
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#include "pci.h"
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static void pci_free_resources(struct pci_dev *dev)
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{
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int i;
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msi_remove_pci_irq_vectors(dev);
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pci_cleanup_rom(dev);
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for (i = 0; i < PCI_NUM_RESOURCES; i++) {
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struct resource *res = dev->resource + i;
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if (res->parent)
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release_resource(res);
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}
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}
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static void pci_stop_dev(struct pci_dev *dev)
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{
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if (dev->is_added) {
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pci_proc_detach_device(dev);
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pci_remove_sysfs_dev_files(dev);
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device_unregister(&dev->dev);
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dev->is_added = 0;
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}
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if (dev->bus->self)
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pcie_aspm_exit_link_state(dev);
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}
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static void pci_destroy_dev(struct pci_dev *dev)
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{
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pci_stop_dev(dev);
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/* Remove the device from the device lists, and prevent any further
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* list accesses from this device */
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down_write(&pci_bus_sem);
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list_del(&dev->bus_list);
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dev->bus_list.next = dev->bus_list.prev = NULL;
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up_write(&pci_bus_sem);
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pci_free_resources(dev);
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pci_dev_put(dev);
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}
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/**
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* pci_remove_device_safe - remove an unused hotplug device
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* @dev: the device to remove
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*
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* Delete the device structure from the device lists and
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* notify userspace (/sbin/hotplug), but only if the device
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* in question is not being used by a driver.
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* Returns 0 on success.
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*/
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#if 0
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int pci_remove_device_safe(struct pci_dev *dev)
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{
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if (pci_dev_driver(dev))
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return -EBUSY;
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pci_destroy_dev(dev);
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return 0;
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}
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#endif /* 0 */
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void pci_remove_bus(struct pci_bus *pci_bus)
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{
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pci_proc_detach_bus(pci_bus);
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down_write(&pci_bus_sem);
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list_del(&pci_bus->node);
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up_write(&pci_bus_sem);
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pci_remove_legacy_files(pci_bus);
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device_remove_file(&pci_bus->dev, &dev_attr_cpuaffinity);
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device_unregister(&pci_bus->dev);
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}
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EXPORT_SYMBOL(pci_remove_bus);
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/**
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* pci_remove_bus_device - remove a PCI device and any children
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* @dev: the device to remove
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*
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* Remove a PCI device from the device lists, informing the drivers
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* that the device has been removed. We also remove any subordinate
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* buses and children in a depth-first manner.
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*
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* For each device we remove, delete the device structure from the
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* device lists, remove the /proc entry, and notify userspace
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* (/sbin/hotplug).
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*/
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void pci_remove_bus_device(struct pci_dev *dev)
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{
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if (dev->subordinate) {
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struct pci_bus *b = dev->subordinate;
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pci_remove_behind_bridge(dev);
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pci_remove_bus(b);
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dev->subordinate = NULL;
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}
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pci_destroy_dev(dev);
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}
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/**
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* pci_remove_behind_bridge - remove all devices behind a PCI bridge
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* @dev: PCI bridge device
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*
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* Remove all devices on the bus, except for the parent bridge.
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* This also removes any child buses, and any devices they may
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* contain in a depth-first manner.
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*/
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void pci_remove_behind_bridge(struct pci_dev *dev)
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{
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struct list_head *l, *n;
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if (dev->subordinate) {
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list_for_each_safe(l, n, &dev->subordinate->devices) {
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struct pci_dev *dev = pci_dev_b(l);
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pci_remove_bus_device(dev);
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}
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}
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}
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static void pci_stop_bus_devices(struct pci_bus *bus)
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{
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struct list_head *l, *n;
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list_for_each_safe(l, n, &bus->devices) {
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struct pci_dev *dev = pci_dev_b(l);
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pci_stop_bus_device(dev);
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}
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}
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/**
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* pci_stop_bus_device - stop a PCI device and any children
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* @dev: the device to stop
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*
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* Stop a PCI device (detach the driver, remove from the global list
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* and so on). This also stop any subordinate buses and children in a
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* depth-first manner.
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*/
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void pci_stop_bus_device(struct pci_dev *dev)
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{
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if (dev->subordinate)
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pci_stop_bus_devices(dev->subordinate);
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pci_stop_dev(dev);
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}
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EXPORT_SYMBOL(pci_remove_bus_device);
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EXPORT_SYMBOL(pci_remove_behind_bridge);
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EXPORT_SYMBOL_GPL(pci_stop_bus_device);
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