[PATCH V7 1/4] PCI/ASPM: Add pci_enable_link_state()

[David E. Box]

From: Michael Bottini <michael.a.bottini@xxxxxxxxxxxxxxx>

Add pci_enable_link_state() to allow devices to change the default BIOS
configured states. Clears the BIOS default settings then sets the new
states and reconfigures the link under the semaphore. Also add
PCIE_LINK_STATE_ALL macro for convenience for callers that want to enable
all link states.

Signed-off-by: Michael Bottini <michael.a.bottini@xxxxxxxxxxxxxxx>
Signed-off-by: David E. Box <david.e.box@xxxxxxxxxxxxxxx>
Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
---
 V7
  - Fix description as suggested by Bjorn
  - Rename function to pci_enable_link_state

 V6
  - No change
 V5
  - Rename to pci_enable_default_link_state and model after
    pci_disable_link_state() as suggested by Bjorn.
  - Add helper PCIE_LINK_STATE_ALL which sets bits for all links states and
    clock pm.
  - Clarify commit language to indicate the function changes the default
    link states (not ASPM policy).
 V4
  - Refactor vmd_enable_apsm() to exit early, making the lines shorter
    and more readable. Suggested by Christoph.
 V3
  - No changes
 V2
  - Use return status to print pci_info message if ASPM cannot be enabled.
  - Add missing static declaration, caught by lkp@xxxxxxxxx
 
 drivers/pci/pcie/aspm.c | 54 +++++++++++++++++++++++++++++++++++++++++
 include/linux/pci.h     |  7 ++++++
 2 files changed, 61 insertions(+)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 53a1fa306e1e..339c686a5094 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -1181,6 +1181,60 @@ int pci_disable_link_state(struct pci_dev *pdev, int state)
 }
 EXPORT_SYMBOL(pci_disable_link_state);
 
+/**
+ * pci_enable_link_state - Clear and set the default device link state so that
+ * the link may be allowed to enter the specified 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. Also note that this does not enable states
+ * disabled by pci_disable_link_state(). Return 0 or a negative errno.
+ *
+ * @pdev: PCI device
+ * @state: Mask of ASPM link states to enable
+ */
+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 enabled 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.
+	 */
+	if (aspm_disabled) {
+		pci_warn(pdev, "can't override BIOS ASPM; OS doesn't have ASPM control\n");
+		return -EPERM;
+	}
+
+	down_read(&pci_bus_sem);
+	mutex_lock(&aspm_lock);
+	link->aspm_default = 0;
+	if (state & PCIE_LINK_STATE_L0S)
+		link->aspm_default |= ASPM_STATE_L0S;
+	if (state & PCIE_LINK_STATE_L1)
+		/* L1 PM substates require L1 */
+		link->aspm_default |= ASPM_STATE_L1 | ASPM_STATE_L1SS;
+	if (state & PCIE_LINK_STATE_L1_1)
+		link->aspm_default |= ASPM_STATE_L1_1;
+	if (state & PCIE_LINK_STATE_L1_2)
+		link->aspm_default |= ASPM_STATE_L1_2;
+	if (state & PCIE_LINK_STATE_L1_1_PCIPM)
+		link->aspm_default |= ASPM_STATE_L1_1_PCIPM;
+	if (state & PCIE_LINK_STATE_L1_2_PCIPM)
+		link->aspm_default |= ASPM_STATE_L1_2_PCIPM;
+	pcie_config_aspm_link(link, policy_to_aspm_state(link));
+
+	link->clkpm_default = (state & PCIE_LINK_STATE_CLKPM) ? 1 : 0;
+	pcie_set_clkpm(link, policy_to_clkpm_state(link));
+	mutex_unlock(&aspm_lock);
+	up_read(&pci_bus_sem);
+
+	return 0;
+}
+EXPORT_SYMBOL(pci_enable_link_state);
+
 static int pcie_aspm_set_policy(const char *val,
 				const struct kernel_param *kp)
 {
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 2bda4a4e47e8..8c35f15e6012 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1651,10 +1651,15 @@ extern bool pcie_ports_native;
 #define PCIE_LINK_STATE_L1_2		BIT(4)
 #define PCIE_LINK_STATE_L1_1_PCIPM	BIT(5)
 #define PCIE_LINK_STATE_L1_2_PCIPM	BIT(6)
+#define PCIE_LINK_STATE_ALL		(PCIE_LINK_STATE_L0S | PCIE_LINK_STATE_L1 |\
+					 PCIE_LINK_STATE_CLKPM | PCIE_LINK_STATE_L1_1 |\
+					 PCIE_LINK_STATE_L1_2 | PCIE_LINK_STATE_L1_1_PCIPM |\
+					 PCIE_LINK_STATE_L1_2_PCIPM)
 
 #ifdef CONFIG_PCIEASPM
 int pci_disable_link_state(struct pci_dev *pdev, int state);
 int pci_disable_link_state_locked(struct pci_dev *pdev, int state);
+int pci_enable_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);
@@ -1663,6 +1668,8 @@ static inline int pci_disable_link_state(struct pci_dev *pdev, int state)
 { return 0; }
 static inline int pci_disable_link_state_locked(struct pci_dev *pdev, int state)
 { return 0; }
+static inline int pci_enable_link_state(struct pci_dev *pdev, int state)
+{ return 0; }
 static inline void pcie_no_aspm(void) { }
 static inline bool pcie_aspm_support_enabled(void) { return false; }
 static inline bool pcie_aspm_enabled(struct pci_dev *pdev) { return false; }
-- 
2.25.1