[PATCH v1 1/1] PCI/ATS: Optimize pci_prg_resp_pasid_required() function

sathyanarayanan.kuppuswamy
2019-10-07T23:35:12Z

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

Currently, pci_prg_resp_pasid_required() function reads the
PASID Required bit status from register every time we call
the function. Since PASID Required bit is a read-only value,
instead of reading it from register every time, read it once and
cache it in struct pci_dev.

Also, since we are caching PASID Required bit in pci_pri_init()
function, move the caching of PRI Capability check result to the same
function. This will group all PRI related caching at one place.

Since "pasid_required" structure member is protected by CONFIG_PRI,
its users should also be protected by same #ifdef. So correct the #ifdef
dependency of pci_prg_resp_pasid_required() function.

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Keith Busch <keith.busch@intel.com>
---
drivers/pci/ats.c | 50 ++++++++++++++++++++++++---------------------
include/linux/pci.h | 1 +
2 files changed, 28 insertions(+), 23 deletions(-)

diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index cb4f62da7b8a..2b5df5ea208f 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -16,6 +16,24 @@

#include "pci.h"

+static void pci_pri_init(struct pci_dev *pdev)
+{
+#ifdef CONFIG_PCI_PRI
+ int pos;
+ u16 status;
+
+ pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
+ if (!pos)
+ return;
+
+ pdev->pri_cap = pos;
+
+ pci_read_config_word(pdev, pos + PCI_PRI_STATUS, &status);
+ if (status & PCI_PRI_STATUS_PASID)
+ pdev->pasid_required = 1;
+#endif
+}
+
void pci_ats_init(struct pci_dev *dev)
{
int pos;
@@ -28,6 +46,8 @@ void pci_ats_init(struct pci_dev *dev)
return;

dev->ats_cap = pos;
+
+ pci_pri_init(dev);
}

/**
@@ -185,12 +205,8 @@ int pci_enable_pri(struct pci_dev *pdev, u32 reqs)
if (WARN_ON(pdev->pri_enabled))
return -EBUSY;

- if (!pri) {
- pri = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
- if (!pri)
- return -EINVAL;
- pdev->pri_cap = pri;
- }
+ if (!pri)
+ return -EINVAL;

pci_read_config_word(pdev, pri + PCI_PRI_STATUS, &status);
if (!(status & PCI_PRI_STATUS_STOPPED))
@@ -425,6 +441,7 @@ int pci_pasid_features(struct pci_dev *pdev)
}
EXPORT_SYMBOL_GPL(pci_pasid_features);

+#ifdef CONFIG_PCI_PRI
/**
* pci_prg_resp_pasid_required - Return PRG Response PASID Required bit
* status.
@@ -432,31 +449,18 @@ EXPORT_SYMBOL_GPL(pci_pasid_features);
*
* Returns 1 if PASID is required in PRG Response Message, 0 otherwise.
*
- * Even though the PRG response PASID status is read from PRI Status
- * Register, since this API will mainly be used by PASID users, this
- * function is defined within #ifdef CONFIG_PCI_PASID instead of
- * CONFIG_PCI_PRI.
+ * Since this API has dependency on both PRI and PASID, protect it
+ * with both CONFIG_PCI_PRI and CONFIG_PCI_PASID.
*/
int pci_prg_resp_pasid_required(struct pci_dev *pdev)
{
- u16 status;
- int pri;
-
if (pdev->is_virtfn)
pdev = pci_physfn(pdev);

- pri = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
- if (!pri)
- return 0;
-
- pci_read_config_word(pdev, pri + PCI_PRI_STATUS, &status);
-
- if (status & PCI_PRI_STATUS_PASID)
- return 1;
-
- return 0;
+ return pdev->pasid_required;
}
EXPORT_SYMBOL_GPL(pci_prg_resp_pasid_required);
+#endif /* CONFIG_PCI_PRI */

#define PASID_NUMBER_SHIFT 8
#define PASID_NUMBER_MASK (0x1f << PASID_NUMBER_SHIFT)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 6542100bd2dd..f1131fee7fcd 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -456,6 +456,7 @@ struct pci_dev {
#ifdef CONFIG_PCI_PRI
u16 pri_cap; /* PRI Capability offset */
u32 pri_reqs_alloc; /* Number of PRI requests allocated */
+ unsigned int pasid_required:1; /* PRG Response PASID Required bit status */
#endif
#ifdef CONFIG_PCI_PASID
u16 pasid_cap; /* PASID Capability offset */
--
2.21.0