pci_disable_link_state() lacks a symmetric pair. Some drivers want to
disable ASPM during certain phases of their operation but then
re-enable it later on. If pci_disable_link_state() is made for the
device, there is currently no way to re-enable the states that were
disabled.
Add pci_enable_link_state() to remove ASPM states from the state
disable mask.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
---
drivers/pci/pcie/aspm.c | 44 +++++++++++++++++++++++++++++++++++++++++
include/linux/pci.h | 2 ++
2 files changed, 46 insertions(+)
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 4727f73a2d0d..aed59ab13c46 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -1165,6 +1165,50 @@ int pci_disable_link_state(struct pci_dev *pdev, int state)
}
EXPORT_SYMBOL(pci_disable_link_state);
+/**
+ * pci_enable_link_state - Re-enable device's link state
+ * @pdev: PCI device
+ * @state: ASPM link states to re-enable
+ *
+ * Enable device's link state that were previously disable so the link is
+ * allowed to enter the specific states. Note that if the BIOS didn't grant
+ * ASPM control to the OS, this does nothing because we can't touch the
+ * LNKCTL register.
+ *
+ * Return: 0 or a negative errno.
+ */
+int pci_enable_link_state(struct pci_dev *pdev, int state)
+{
+ struct pcie_link_state *link = pcie_aspm_get_link(pdev);
+
+ if (!link)
+ return -EINVAL;
+ /*
+ * A driver requested that ASPM be disabled on this device, but
+ * if we don't have permission to manage ASPM (e.g., on ACPI
+ * systems we have to observe the FADT ACPI_FADT_NO_ASPM bit and
+ * the _OSC method), we can't honor that request. Windows has
+ * a similar mechanism using "PciASPMOptOut", which is also
+ * ignored in this situation.
+ */
+ if (aspm_disabled) {
+ pci_warn(pdev, "can't enable ASPM; OS doesn't have ASPM control\n");
+ return -EPERM;
+ }
+
+ mutex_lock(&aspm_lock);
+ link->aspm_disable &= ~pci_link_state_mask(state);
+ pcie_config_aspm_link(link, policy_to_aspm_state(link));
+
+ if (state & PCIE_LINK_STATE_CLKPM)
+ link->clkpm_disable = 0;
+ pcie_set_clkpm(link, policy_to_clkpm_state(link));
+ mutex_unlock(&aspm_lock);
+
+ return 0;
+}
+EXPORT_SYMBOL(pci_enable_link_state);
+
/**
* pci_set_default_link_state - Set the default device link state
* @pdev: PCI device
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 5597e97a086d..aec259d12ca0 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1777,11 +1777,13 @@ extern bool pcie_ports_native;
int pci_disable_link_state(struct pci_dev *pdev, int state);
int pci_disable_link_state_locked(struct pci_dev *pdev, int state);
#ifdef CONFIG_PCIEASPM
+int pci_enable_link_state(struct pci_dev *pdev, int state);
int pci_set_default_link_state(struct pci_dev *pdev, int state);
void pcie_no_aspm(void);
bool pcie_aspm_support_enabled(void);
bool pcie_aspm_enabled(struct pci_dev *pdev);
#else
+static inline int pci_enable_link_state(struct pci_dev *pdev, int state) { return -EOPNOTSUPP; }
static inline int pci_set_default_link_state(struct pci_dev *pdev, int state)
{ return 0; }
static inline void pcie_no_aspm(void) { }
--
2.30.2
