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authorMatthew Garrett <mjg@redhat.com>2011-11-10 16:38:33 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-02-06 09:24:01 -0800
commit6cac12dfab9c57a4f76821412224b226a9b08dff (patch)
treeb08160d929d2e0c0b5727487c8e419fe63445419
parent5d14e472c60de8791259a0dbb8ba5252d0862a63 (diff)
PCI: Rework ASPM disable code
commit 3c076351c4027a56d5005a39a0b518a4ba393ce2 upstream. Right now we forcibly clear ASPM state on all devices if the BIOS indicates that the feature isn't supported. Based on the Microsoft presentation "PCI Express In Depth for Windows Vista and Beyond", I'm starting to think that this may be an error. The implication is that unless the platform grants full control via _OSC, Windows will not touch any PCIe features - including ASPM. In that case clearing ASPM state would be an error unless the platform has granted us that control. This patch reworks the ASPM disabling code such that the actual clearing of state is triggered by a successful handoff of PCIe control to the OS. The general ASPM code undergoes some changes in order to ensure that the ability to clear the bits isn't overridden by ASPM having already been disabled. Further, this theoretically now allows for situations where only a subset of PCIe roots hand over control, leaving the others in the BIOS state. It's difficult to know for sure that this is the right thing to do - there's zero public documentation on the interaction between all of these components. But enough vendors enable ASPM on platforms and then set this bit that it seems likely that they're expecting the OS to leave them alone. Measured to save around 5W on an idle Thinkpad X220. Signed-off-by: Matthew Garrett <mjg@redhat.com> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/acpi/pci_root.c7
-rw-r--r--drivers/pci/pci-acpi.c1
-rw-r--r--drivers/pci/pcie/aspm.c58
-rw-r--r--include/linux/pci-aspm.h4
4 files changed, 46 insertions, 24 deletions
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index d06078d660ad..dfafecbddb53 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -595,6 +595,13 @@ static int __devinit acpi_pci_root_add(struct acpi_device *device)
if (ACPI_SUCCESS(status)) {
dev_info(root->bus->bridge,
"ACPI _OSC control (0x%02x) granted\n", flags);
+ if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM) {
+ /*
+ * We have ASPM control, but the FADT indicates
+ * that it's unsupported. Clear it.
+ */
+ pcie_clear_aspm(root->bus);
+ }
} else {
dev_info(root->bus->bridge,
"ACPI _OSC request failed (%s), "
diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index d36f41ea8cbf..56b04bc80a12 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -393,7 +393,6 @@ static int __init acpi_pci_init(void)
if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM) {
printk(KERN_INFO"ACPI FADT declares the system doesn't support PCIe ASPM, so disable it\n");
- pcie_clear_aspm();
pcie_no_aspm();
}
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 6892601fc76f..e25af67f685d 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -68,7 +68,7 @@ struct pcie_link_state {
struct aspm_latency acceptable[8];
};
-static int aspm_disabled, aspm_force, aspm_clear_state;
+static int aspm_disabled, aspm_force;
static bool aspm_support_enabled = true;
static DEFINE_MUTEX(aspm_lock);
static LIST_HEAD(link_list);
@@ -500,9 +500,6 @@ static int pcie_aspm_sanity_check(struct pci_dev *pdev)
int pos;
u32 reg32;
- if (aspm_clear_state)
- return -EINVAL;
-
/*
* Some functions in a slot might not all be PCIe functions,
* very strange. Disable ASPM for the whole slot
@@ -574,9 +571,6 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
pdev->pcie_type != PCI_EXP_TYPE_DOWNSTREAM)
return;
- if (aspm_disabled && !aspm_clear_state)
- return;
-
/* VIA has a strange chipset, root port is under a bridge */
if (pdev->pcie_type == PCI_EXP_TYPE_ROOT_PORT &&
pdev->bus->self)
@@ -608,7 +602,7 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
* the BIOS's expectation, we'll do so once pci_enable_device() is
* called.
*/
- if (aspm_policy != POLICY_POWERSAVE || aspm_clear_state) {
+ if (aspm_policy != POLICY_POWERSAVE) {
pcie_config_aspm_path(link);
pcie_set_clkpm(link, policy_to_clkpm_state(link));
}
@@ -649,8 +643,7 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
struct pci_dev *parent = pdev->bus->self;
struct pcie_link_state *link, *root, *parent_link;
- if ((aspm_disabled && !aspm_clear_state) || !pci_is_pcie(pdev) ||
- !parent || !parent->link_state)
+ if (!pci_is_pcie(pdev) || !parent || !parent->link_state)
return;
if ((parent->pcie_type != PCI_EXP_TYPE_ROOT_PORT) &&
(parent->pcie_type != PCI_EXP_TYPE_DOWNSTREAM))
@@ -734,13 +727,18 @@ void pcie_aspm_powersave_config_link(struct pci_dev *pdev)
* pci_disable_link_state - disable pci device's link state, so the link will
* never enter specific states
*/
-static void __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem)
+static void __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem,
+ bool force)
{
struct pci_dev *parent = pdev->bus->self;
struct pcie_link_state *link;
- if (aspm_disabled || !pci_is_pcie(pdev))
+ if (aspm_disabled && !force)
+ return;
+
+ if (!pci_is_pcie(pdev))
return;
+
if (pdev->pcie_type == PCI_EXP_TYPE_ROOT_PORT ||
pdev->pcie_type == PCI_EXP_TYPE_DOWNSTREAM)
parent = pdev;
@@ -768,16 +766,31 @@ static void __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem)
void pci_disable_link_state_locked(struct pci_dev *pdev, int state)
{
- __pci_disable_link_state(pdev, state, false);
+ __pci_disable_link_state(pdev, state, false, false);
}
EXPORT_SYMBOL(pci_disable_link_state_locked);
void pci_disable_link_state(struct pci_dev *pdev, int state)
{
- __pci_disable_link_state(pdev, state, true);
+ __pci_disable_link_state(pdev, state, true, false);
}
EXPORT_SYMBOL(pci_disable_link_state);
+void pcie_clear_aspm(struct pci_bus *bus)
+{
+ struct pci_dev *child;
+
+ /*
+ * Clear any ASPM setup that the firmware has carried out on this bus
+ */
+ list_for_each_entry(child, &bus->devices, bus_list) {
+ __pci_disable_link_state(child, PCIE_LINK_STATE_L0S |
+ PCIE_LINK_STATE_L1 |
+ PCIE_LINK_STATE_CLKPM,
+ false, true);
+ }
+}
+
static int pcie_aspm_set_policy(const char *val, struct kernel_param *kp)
{
int i;
@@ -935,6 +948,7 @@ void pcie_aspm_remove_sysfs_dev_files(struct pci_dev *pdev)
static int __init pcie_aspm_disable(char *str)
{
if (!strcmp(str, "off")) {
+ aspm_policy = POLICY_DEFAULT;
aspm_disabled = 1;
aspm_support_enabled = false;
printk(KERN_INFO "PCIe ASPM is disabled\n");
@@ -947,16 +961,18 @@ static int __init pcie_aspm_disable(char *str)
__setup("pcie_aspm=", pcie_aspm_disable);
-void pcie_clear_aspm(void)
-{
- if (!aspm_force)
- aspm_clear_state = 1;
-}
-
void pcie_no_aspm(void)
{
- if (!aspm_force)
+ /*
+ * Disabling ASPM is intended to prevent the kernel from modifying
+ * existing hardware state, not to clear existing state. To that end:
+ * (a) set policy to POLICY_DEFAULT in order to avoid changing state
+ * (b) prevent userspace from changing policy
+ */
+ if (!aspm_force) {
+ aspm_policy = POLICY_DEFAULT;
aspm_disabled = 1;
+ }
}
/**
diff --git a/include/linux/pci-aspm.h b/include/linux/pci-aspm.h
index 7cea7b6c1413..c8320144fe79 100644
--- a/include/linux/pci-aspm.h
+++ b/include/linux/pci-aspm.h
@@ -29,7 +29,7 @@ extern void pcie_aspm_pm_state_change(struct pci_dev *pdev);
extern void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
extern void pci_disable_link_state(struct pci_dev *pdev, int state);
extern void pci_disable_link_state_locked(struct pci_dev *pdev, int state);
-extern void pcie_clear_aspm(void);
+extern void pcie_clear_aspm(struct pci_bus *bus);
extern void pcie_no_aspm(void);
#else
static inline void pcie_aspm_init_link_state(struct pci_dev *pdev)
@@ -47,7 +47,7 @@ static inline void pcie_aspm_powersave_config_link(struct pci_dev *pdev)
static inline void pci_disable_link_state(struct pci_dev *pdev, int state)
{
}
-static inline void pcie_clear_aspm(void)
+static inline void pcie_clear_aspm(struct pci_bus *bus)
{
}
static inline void pcie_no_aspm(void)