PCI: add PCI Express ASPM support

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>

1 files changed, 56 insertions, 0 deletions

diff --git a/include/linux/pci-aspm.h b/include/linux/pci-aspm.h
new file mode 100644
index 000000000000..a1a1e618e996
--- /dev/null
+++ b/include/linux/pci-aspm.h
@@ -0,0 +1,56 @@
+/*
+ *      aspm.h
+ *
+ *      PCI Express ASPM defines and function prototypes
+ *
+ *      Copyright (C) 2007 Intel Corp.
+ *              Zhang Yanmin (yanmin.zhang@intel.com)
+ *              Shaohua Li (shaohua.li@intel.com)
+ *
+ *      For more information, please consult the following manuals (look at
+ *      http://www.pcisig.com/ for how to get them):
+ *
+ *      PCI Express Specification
+ */
+
+#ifndef LINUX_ASPM_H
+#define LINUX_ASPM_H
+
+#include <linux/pci.h>
+
+#define PCIE_LINK_STATE_L0S     1
+#define PCIE_LINK_STATE_L1      2
+#define PCIE_LINK_STATE_CLKPM   4
+
+#ifdef CONFIG_PCIEASPM
+extern void pcie_aspm_init_link_state(struct pci_dev *pdev);
+extern void pcie_aspm_exit_link_state(struct pci_dev *pdev);
+extern void pcie_aspm_pm_state_change(struct pci_dev *pdev);
+extern void pci_disable_link_state(struct pci_dev *pdev, int state);
+#else
+static inline void pcie_aspm_init_link_state(struct pci_dev *pdev)
+{
+}
+static inline void pcie_aspm_exit_link_state(struct pci_dev *pdev)
+{
+}
+static inline void pcie_aspm_pm_state_change(struct pci_dev *pdev)
+{
+}
+static inline void pci_disable_link_state(struct pci_dev *pdev, int state)
+{
+}
+#endif
+
+#ifdef CONFIG_PCIEASPM_DEBUG /* this depends on CONFIG_PCIEASPM */
+extern void pcie_aspm_create_sysfs_dev_files(struct pci_dev *pdev);
+extern void pcie_aspm_remove_sysfs_dev_files(struct pci_dev *pdev);
+#else
+static inline void pcie_aspm_create_sysfs_dev_files(struct pci_dev *pdev)
+{
+}
+static inline void pcie_aspm_remove_sysfs_dev_files(struct pci_dev *pdev)
+{
+}
+#endif
+#endif /* LINUX_ASPM_H */