linux-kernel - [PATCH] PCI/ASPM: pci_enable_link_state: Add argument to acquire bus lock

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Date:   Tue, 21 Mar 2023 16:38:49 -0700
From:   "David E. Box" <david.e.box@...ux.intel.com>
To:     david.e.box@...ux.intel.com, ville.syrjala@...ux.intel.com,
        nirmal.patel@...ux.intel.com, jonathan.derrick@...ux.dev,
        lorenzo.pieralisi@....com, hch@...radead.org, kw@...ux.com,
        robh@...nel.org, bhelgaas@...gle.com, michael.a.bottini@...el.com,
        rafael@...nel.org
Cc:     me@...ityamohan.in, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org
Subject: [PATCH] PCI/ASPM: pci_enable_link_state: Add argument to acquire bus lock

The VMD driver calls pci_enabled_link_state as a callback from
pci_bus_walk. Both will acquire the pci_bus_sem lock leading to a lockdep
warning. Add an argument to pci_enable_link_state to set whether the lock
should be acquired. In the VMD driver, set the argument to false since the
lock will already be obtained by pci_bus_walk.

Reported-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
Fixes: de82f60f9c86 ("PCI/ASPM: Add pci_enable_link_state()")
Link: https://lore.kernel.org/linux-pci/ZBjko%2FifunIwsK2v@intel.com/
Signed-off-by: David E. Box <david.e.box@...ux.intel.com>
---
 drivers/pci/controller/vmd.c | 2 +-
 drivers/pci/pcie/aspm.c      | 9 ++++++---
 include/linux/pci.h          | 5 +++--
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
index 990630ec57c6..45aa35744eae 100644
--- a/drivers/pci/controller/vmd.c
+++ b/drivers/pci/controller/vmd.c
@@ -737,7 +737,7 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
 	if (!(features & VMD_FEAT_BIOS_PM_QUIRK))
 		return 0;
 
-	pci_enable_link_state(pdev, PCIE_LINK_STATE_ALL);
+	pci_enable_link_state(pdev, PCIE_LINK_STATE_ALL, false);
 
 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_LTR);
 	if (!pos)
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 66d7514ca111..5b5a600bb864 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -1147,8 +1147,9 @@ EXPORT_SYMBOL(pci_disable_link_state);
  *
  * @pdev: PCI device
  * @state: Mask of ASPM link states to enable
+ * @sem: Boolean to acquire/release pci_bus_sem
  */
-int pci_enable_link_state(struct pci_dev *pdev, int state)
+int pci_enable_link_state(struct pci_dev *pdev, int state, bool sem)
 {
 	struct pcie_link_state *link = pcie_aspm_get_link(pdev);
 
@@ -1165,7 +1166,8 @@ int pci_enable_link_state(struct pci_dev *pdev, int state)
 		return -EPERM;
 	}
 
-	down_read(&pci_bus_sem);
+	if (sem)
+		down_read(&pci_bus_sem);
 	mutex_lock(&aspm_lock);
 	link->aspm_default = 0;
 	if (state & PCIE_LINK_STATE_L0S)
@@ -1186,7 +1188,8 @@ int pci_enable_link_state(struct pci_dev *pdev, int state)
 	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);
+	if (sem)
+		up_read(&pci_bus_sem);
 
 	return 0;
 }
diff --git a/include/linux/pci.h b/include/linux/pci.h
index fafd8020c6d7..a6f9f24b39fd 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1707,7 +1707,7 @@ extern bool pcie_ports_native;
 #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);
+int pci_enable_link_state(struct pci_dev *pdev, int state, bool sem);
 void pcie_no_aspm(void);
 bool pcie_aspm_support_enabled(void);
 bool pcie_aspm_enabled(struct pci_dev *pdev);
@@ -1716,7 +1716,8 @@ 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)
+static inline int
+pci_enable_link_state(struct pci_dev *pdev, int state, bool sem)
 { return 0; }
 static inline void pcie_no_aspm(void) { }
 static inline bool pcie_aspm_support_enabled(void) { return false; }
-- 
2.34.1