PCI: Cache ACS capability offset in device

Currently the ACS capability is being looked up at a number of places. Read
and store it once at enumeration so that it can be used by all later.  No
functional change intended.

Link: https://lore.kernel.org/r/20200707224604.3737893-2-rajatja@google.comSigned-off-by: Rajat Jain <rajatja@google.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/p2pdma.c

@@ -253,7 +253,7 @@ static int pci_bridge_has_acs_redir(struct pci_dev *pdev)
 	int pos;
 	u16 ctrl;
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS);
+	pos = pdev->acs_cap;
 	if (!pos)
 		return 0;
 

drivers/pci/pci.c

@@ -831,7 +831,7 @@ static void pci_disable_acs_redir(struct pci_dev *dev)
 	if (!pci_dev_specific_disable_acs_redir(dev))
 		return;
 
-	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
+	pos = dev->acs_cap;
 	if (!pos) {
 		pci_warn(dev, "cannot disable ACS redirect for this hardware as it does not have ACS capabilities\n");
 		return;
@@ -857,7 +857,7 @@ static void pci_std_enable_acs(struct pci_dev *dev)
 	u16 cap;
 	u16 ctrl;
 
-	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
+	pos = dev->acs_cap;
 	if (!pos)
 		return;
 
@@ -883,7 +883,7 @@ static void pci_std_enable_acs(struct pci_dev *dev)
  * pci_enable_acs - enable ACS if hardware support it
  * @dev: the PCI device
  */
-void pci_enable_acs(struct pci_dev *dev)
+static void pci_enable_acs(struct pci_dev *dev)
 {
 	if (!pci_acs_enable)
 		goto disable_acs_redir;
@@ -3362,7 +3362,7 @@ static bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags)
 	int pos;
 	u16 cap, ctrl;
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS);
+	pos = pdev->acs_cap;
 	if (!pos)
 		return false;
 
@@ -3487,6 +3487,18 @@ bool pci_acs_path_enabled(struct pci_dev *start,
 	return true;
 }
 
+/**
+ * pci_acs_init - Initialize ACS if hardware supports it
+ * @dev: the PCI device
+ */
+void pci_acs_init(struct pci_dev *dev)
+{
+	dev->acs_cap = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
+
+	if (dev->acs_cap)
+		pci_enable_acs(dev);
+}
+
 /**
  * pci_rebar_find_pos - find position of resize ctrl reg for BAR
  * @pdev: PCI device

drivers/pci/pci.h

@@ -532,7 +532,7 @@ static inline resource_size_t pci_resource_alignment(struct pci_dev *dev,
 	return resource_alignment(res);
 }
 
-void pci_enable_acs(struct pci_dev *dev);
+void pci_acs_init(struct pci_dev *dev);
 #ifdef CONFIG_PCI_QUIRKS
 int pci_dev_specific_acs_enabled(struct pci_dev *dev, u16 acs_flags);
 int pci_dev_specific_enable_acs(struct pci_dev *dev);

drivers/pci/probe.c

@@ -2390,7 +2390,7 @@ static void pci_init_capabilities(struct pci_dev *dev)
 	pci_ats_init(dev);		/* Address Translation Services */
 	pci_pri_init(dev);		/* Page Request Interface */
 	pci_pasid_init(dev);		/* Process Address Space ID */
-	pci_enable_acs(dev);		/* Enable ACS P2P upstream forwarding */
+	pci_acs_init(dev);		/* Access Control Services */
 	pci_ptm_init(dev);		/* Precision Time Measurement */
 	pci_aer_init(dev);		/* Advanced Error Reporting */
 	pci_dpc_init(dev);		/* Downstream Port Containment */

drivers/pci/quirks.c

@@ -4653,7 +4653,7 @@ static int pci_quirk_intel_spt_pch_acs(struct pci_dev *dev, u16 acs_flags)
 	if (!pci_quirk_intel_spt_pch_acs_match(dev))
 		return -ENOTTY;
 
-	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
+	pos = dev->acs_cap;
 	if (!pos)
 		return -ENOTTY;
 
@@ -4961,7 +4961,7 @@ static int pci_quirk_enable_intel_spt_pch_acs(struct pci_dev *dev)
 	if (!pci_quirk_intel_spt_pch_acs_match(dev))
 		return -ENOTTY;
 
-	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
+	pos = dev->acs_cap;
 	if (!pos)
 		return -ENOTTY;
 
@@ -4988,7 +4988,7 @@ static int pci_quirk_disable_intel_spt_pch_acs_redir(struct pci_dev *dev)
 	if (!pci_quirk_intel_spt_pch_acs_match(dev))
 		return -ENOTTY;
 
-	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
+	pos = dev->acs_cap;
 	if (!pos)
 		return -ENOTTY;
 
@@ -5355,7 +5355,7 @@ int pci_idt_bus_quirk(struct pci_bus *bus, int devfn, u32 *l, int timeout)
 	bool found;
 	struct pci_dev *bridge = bus->self;
 
-	pos = pci_find_ext_capability(bridge, PCI_EXT_CAP_ID_ACS);
+	pos = bridge->acs_cap;
 
 	/* Disable ACS SV before initial config reads */
 	if (pos) {

include/linux/pci.h

@@ -486,6 +486,7 @@ struct pci_dev {
 #ifdef CONFIG_PCI_P2PDMA
 	struct pci_p2pdma *p2pdma;
 #endif
+	u16		acs_cap;	/* ACS Capability offset */
 	phys_addr_t	rom;		/* Physical address if not from BAR */
 	size_t		romlen;		/* Length if not from BAR */
 	char		*driver_override; /* Driver name to force a match */