[PATCH 4/5] PCI/ATS: Cache PRI Capability offset

[Bjorn Helgaas]

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>

Previously each PRI interface searched for the PRI 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_pri() rather than adding pci_pri_init()]
Link: https://lore.kernel.org/r/0c5495d376faf6dbb8eb2165204c474438aaae65.156
7029860.git.sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
---
 drivers/pci/ats.c   | 52 ++++++++++++++++++++++-----------------------
 include/linux/pci.h |  1 +
 2 files changed, 27 insertions(+), 26 deletions(-)

diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index 920deeccf38d..bc463e2ecc61 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -169,7 +169,7 @@ int pci_enable_pri(struct pci_dev *pdev, u32 reqs)
 {
 	u16 control, status;
 	u32 max_requests;
-	int pos;
+	int pri = pdev->pri_cap;
 
 	/*
 	 * VFs must not implement the PRI Capability.  If their PF
@@ -185,21 +185,24 @@ int pci_enable_pri(struct pci_dev *pdev, u32 reqs)
 	if (WARN_ON(pdev->pri_enabled))
 		return -EBUSY;
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
-	if (!pos)
-		return -EINVAL;
+	if (!pri) {
+		pri = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
+		if (!pri)
+			return -EINVAL;
+		pdev->pri_cap = pri;
+	}
 
-	pci_read_config_word(pdev, pos + PCI_PRI_STATUS, &status);
+	pci_read_config_word(pdev, pri + PCI_PRI_STATUS, &status);
 	if (!(status & PCI_PRI_STATUS_STOPPED))
 		return -EBUSY;
 
-	pci_read_config_dword(pdev, pos + PCI_PRI_MAX_REQ, &max_requests);
+	pci_read_config_dword(pdev, pri + PCI_PRI_MAX_REQ, &max_requests);
 	reqs = min(max_requests, reqs);
 	pdev->pri_reqs_alloc = reqs;
-	pci_write_config_dword(pdev, pos + PCI_PRI_ALLOC_REQ, reqs);
+	pci_write_config_dword(pdev, pri + PCI_PRI_ALLOC_REQ, reqs);
 
 	control = PCI_PRI_CTRL_ENABLE;
-	pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);
+	pci_write_config_word(pdev, pri + PCI_PRI_CTRL, control);
 
 	pdev->pri_enabled = 1;
 
@@ -216,7 +219,7 @@ EXPORT_SYMBOL_GPL(pci_enable_pri);
 void pci_disable_pri(struct pci_dev *pdev)
 {
 	u16 control;
-	int pos;
+	int pri = pdev->pri_cap;
 
 	/* VFs share the PF PRI */
 	if (pdev->is_virtfn)
@@ -225,13 +228,12 @@ void pci_disable_pri(struct pci_dev *pdev)
 	if (WARN_ON(!pdev->pri_enabled))
 		return;
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
-	if (!pos)
+	if (!pri)
 		return;
 
-	pci_read_config_word(pdev, pos + PCI_PRI_CTRL, &control);
+	pci_read_config_word(pdev, pri + PCI_PRI_CTRL, &control);
 	control &= ~PCI_PRI_CTRL_ENABLE;
-	pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);
+	pci_write_config_word(pdev, pri + PCI_PRI_CTRL, control);
 
 	pdev->pri_enabled = 0;
 }
@@ -245,7 +247,7 @@ void pci_restore_pri_state(struct pci_dev *pdev)
 {
 	u16 control = PCI_PRI_CTRL_ENABLE;
 	u32 reqs = pdev->pri_reqs_alloc;
-	int pos;
+	int pri = pdev->pri_cap;
 
 	if (pdev->is_virtfn)
 		return;
@@ -253,12 +255,11 @@ void pci_restore_pri_state(struct pci_dev *pdev)
 	if (!pdev->pri_enabled)
 		return;
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
-	if (!pos)
+	if (!pri)
 		return;
 
-	pci_write_config_dword(pdev, pos + PCI_PRI_ALLOC_REQ, reqs);
-	pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);
+	pci_write_config_dword(pdev, pri + PCI_PRI_ALLOC_REQ, reqs);
+	pci_write_config_word(pdev, pri + PCI_PRI_CTRL, control);
 }
 EXPORT_SYMBOL_GPL(pci_restore_pri_state);
 
@@ -272,7 +273,7 @@ EXPORT_SYMBOL_GPL(pci_restore_pri_state);
 int pci_reset_pri(struct pci_dev *pdev)
 {
 	u16 control;
-	int pos;
+	int pri = pdev->pri_cap;
 
 	if (pdev->is_virtfn)
 		return 0;
@@ -280,12 +281,11 @@ int pci_reset_pri(struct pci_dev *pdev)
 	if (WARN_ON(pdev->pri_enabled))
 		return -EBUSY;
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
-	if (!pos)
+	if (!pri)
 		return -EINVAL;
 
 	control = PCI_PRI_CTRL_RESET;
-	pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);
+	pci_write_config_word(pdev, pri + PCI_PRI_CTRL, control);
 
 	return 0;
 }
@@ -440,16 +440,16 @@ EXPORT_SYMBOL_GPL(pci_pasid_features);
 int pci_prg_resp_pasid_required(struct pci_dev *pdev)
 {
 	u16 status;
-	int pos;
+	int pri;
 
 	if (pdev->is_virtfn)
 		pdev = pci_physfn(pdev);
 
-	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
-	if (!pos)
+	pri = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
+	if (!pri)
 		return 0;
 
-	pci_read_config_word(pdev, pos + PCI_PRI_STATUS, &status);
+	pci_read_config_word(pdev, pri + PCI_PRI_STATUS, &status);
 
 	if (status & PCI_PRI_STATUS_PASID)
 		return 1;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index a73e8d28a896..c81a24172b14 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -454,6 +454,7 @@ struct pci_dev {
 	u8		ats_stu;	/* ATS Smallest Translation Unit */
 #endif
 #ifdef CONFIG_PCI_PRI
+	u16		pri_cap;	/* PRI Capability offset */
 	u32		pri_reqs_alloc; /* Number of PRI requests allocated */
 #endif
 #ifdef CONFIG_PCI_PASID
-- 
2.23.0.187.g17f5b7556c-goog