[PATCH 5/5] PCI/ATS: Cache PASID Capability offset

[Bjorn Helgaas]

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>

Previously each PASID interface searched for the PASID Capability.  Cache
the capability offset the first time we use it instead of searching each
time.

[bhelgaas: commit log, reorder patch to later, save offset directly in
pci_enable_pasid() rather than adding pci_pasid_init()]
Link: https://lore.kernel.org/r/4957778959fa34eab3e8b3065d1951989c61cb0f.1567029860.git.sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
---
 drivers/pci/ats.c   | 43 +++++++++++++++++++++----------------------
 include/linux/pci.h |  1 +
 2 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index bc463e2ecc61..cb4f62da7b8a 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -305,7 +305,7 @@ EXPORT_SYMBOL_GPL(pci_reset_pri);
 int pci_enable_pasid(struct pci_dev *pdev, int features)
 {
 	u16 control, supported;
-	int pos;
+	int pasid = pdev->pasid_cap;
 
 	/*
 	 * VFs must not implement the PASID Capability, but if a PF
@@ -323,11 +323,14 @@ int pci_enable_pasid(struct pci_dev *pdev, int features)
 	if (!pdev->eetlp_prefix_path)
 		return -EINVAL;
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
-	if (!pos)
-		return -EINVAL;
+	if (!pasid) {
+		pasid = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
+		if (!pasid)
+			return -EINVAL;
+		pdev->pasid_cap = pasid;
+	}
 
-	pci_read_config_word(pdev, pos + PCI_PASID_CAP, &supported);
+	pci_read_config_word(pdev, pasid + PCI_PASID_CAP, &supported);
 	supported &= PCI_PASID_CAP_EXEC | PCI_PASID_CAP_PRIV;
 
 	/* User wants to enable anything unsupported? */
@@ -337,7 +340,7 @@ int pci_enable_pasid(struct pci_dev *pdev, int features)
 	control = PCI_PASID_CTRL_ENABLE | features;
 	pdev->pasid_features = features;
 
-	pci_write_config_word(pdev, pos + PCI_PASID_CTRL, control);
+	pci_write_config_word(pdev, pasid + PCI_PASID_CTRL, control);
 
 	pdev->pasid_enabled = 1;
 
@@ -352,7 +355,7 @@ EXPORT_SYMBOL_GPL(pci_enable_pasid);
 void pci_disable_pasid(struct pci_dev *pdev)
 {
 	u16 control = 0;
-	int pos;
+	int pasid = pdev->pasid_cap;
 
 	/* VFs share the PF PASID configuration */
 	if (pdev->is_virtfn)
@@ -361,11 +364,10 @@ void pci_disable_pasid(struct pci_dev *pdev)
 	if (WARN_ON(!pdev->pasid_enabled))
 		return;
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
-	if (!pos)
+	if (!pasid)
 		return;
 
-	pci_write_config_word(pdev, pos + PCI_PASID_CTRL, control);
+	pci_write_config_word(pdev, pasid + PCI_PASID_CTRL, control);
 
 	pdev->pasid_enabled = 0;
 }
@@ -378,7 +380,7 @@ EXPORT_SYMBOL_GPL(pci_disable_pasid);
 void pci_restore_pasid_state(struct pci_dev *pdev)
 {
 	u16 control;
-	int pos;
+	int pasid = pdev->pasid_cap;
 
 	if (pdev->is_virtfn)
 		return;
@@ -386,12 +388,11 @@ void pci_restore_pasid_state(struct pci_dev *pdev)
 	if (!pdev->pasid_enabled)
 		return;
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
-	if (!pos)
+	if (!pasid)
 		return;
 
 	control = PCI_PASID_CTRL_ENABLE | pdev->pasid_features;
-	pci_write_config_word(pdev, pos + PCI_PASID_CTRL, control);
+	pci_write_config_word(pdev, pasid + PCI_PASID_CTRL, control);
 }
 EXPORT_SYMBOL_GPL(pci_restore_pasid_state);
 
@@ -408,16 +409,15 @@ EXPORT_SYMBOL_GPL(pci_restore_pasid_state);
 int pci_pasid_features(struct pci_dev *pdev)
 {
 	u16 supported;
-	int pos;
+	int pasid = pdev->pasid_cap;
 
 	if (pdev->is_virtfn)
 		pdev = pci_physfn(pdev);
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
-	if (!pos)
+	if (!pasid)
 		return -EINVAL;
 
-	pci_read_config_word(pdev, pos + PCI_PASID_CAP, &supported);
+	pci_read_config_word(pdev, pasid + PCI_PASID_CAP, &supported);
 
 	supported &= PCI_PASID_CAP_EXEC | PCI_PASID_CAP_PRIV;
 
@@ -470,16 +470,15 @@ EXPORT_SYMBOL_GPL(pci_prg_resp_pasid_required);
 int pci_max_pasids(struct pci_dev *pdev)
 {
 	u16 supported;
-	int pos;
+	int pasid = pdev->pasid_cap;
 
 	if (pdev->is_virtfn)
 		pdev = pci_physfn(pdev);
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
-	if (!pos)
+	if (!pasid)
 		return -EINVAL;
 
-	pci_read_config_word(pdev, pos + PCI_PASID_CAP, &supported);
+	pci_read_config_word(pdev, pasid + PCI_PASID_CAP, &supported);
 
 	supported = (supported & PASID_NUMBER_MASK) >> PASID_NUMBER_SHIFT;
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index c81a24172b14..7ddbb6445e1a 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -458,6 +458,7 @@ struct pci_dev {
 	u32		pri_reqs_alloc; /* Number of PRI requests allocated */
 #endif
 #ifdef CONFIG_PCI_PASID
+	u16		pasid_cap;	/* PASID Capability offset */
 	u16		pasid_features;
 #endif
 #ifdef CONFIG_PCI_P2PDMA
-- 
2.23.0.187.g17f5b7556c-goog