PCI: Cache PCIe Device Capabilities register

Add a new member called devcap in struct pci_dev for caching the PCIe
Device Capabilities register to avoid reading PCI_EXP_DEVCAP multiple
times.

Refactor pcie_has_flr() to use cached device capabilities.

Link: https://lore.kernel.org/r/20210817180500.1253-2-ameynarkhede03@gmail.com
Signed-off-by: Amey Narkhede <ameynarkhede03@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index aacf575..b7a9f68 100644 (file)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -31,6 +31,7 @@
 #include <linux/vmalloc.h>
 #include <asm/dma.h>
 #include <linux/aer.h>
+#include <linux/bitfield.h>
 #include "pci.h"
 
 DEFINE_MUTEX(pci_slot_mutex);
@@ -4630,13 +4631,10 @@ EXPORT_SYMBOL(pci_wait_for_pending_transaction);
  */
 bool pcie_has_flr(struct pci_dev *dev)
 {
-       u32 cap;
-
        if (dev->dev_flags & PCI_DEV_FLAGS_NO_FLR_RESET)
                return false;
 
-       pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, &cap);
-       return cap & PCI_EXP_DEVCAP_FLR;
+       return FIELD_GET(PCI_EXP_DEVCAP_FLR, dev->devcap) == 1;
 }
 EXPORT_SYMBOL_GPL(pcie_has_flr);
 

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 79177ac..81eb88a 100644 (file)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -19,6 +19,7 @@
 #include <linux/hypervisor.h>
 #include <linux/irqdomain.h>
 #include <linux/pm_runtime.h>
+#include <linux/bitfield.h>
 #include "pci.h"
 
 #define CARDBUS_LATENCY_TIMER  176     /* secondary latency timer */
@@ -1498,8 +1499,8 @@ void set_pcie_port_type(struct pci_dev *pdev)
        pdev->pcie_cap = pos;
        pci_read_config_word(pdev, pos + PCI_EXP_FLAGS, &reg16);
        pdev->pcie_flags_reg = reg16;
-       pci_read_config_word(pdev, pos + PCI_EXP_DEVCAP, &reg16);
-       pdev->pcie_mpss = reg16 & PCI_EXP_DEVCAP_PAYLOAD;
+       pci_read_config_dword(pdev, pos + PCI_EXP_DEVCAP, &pdev->devcap);
+       pdev->pcie_mpss = FIELD_GET(PCI_EXP_DEVCAP_PAYLOAD, pdev->devcap);
 
        parent = pci_upstream_bridge(pdev);
        if (!parent)

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 540b377..1179c0e 100644 (file)
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -333,6 +333,7 @@ struct pci_dev {
        struct rcec_ea  *rcec_ea;       /* RCEC cached endpoint association */
        struct pci_dev  *rcec;          /* Associated RCEC device */
 #endif
+       u32             devcap;         /* PCIe Device Capabilities */
        u8              pcie_cap;       /* PCIe capability offset */
        u8              msi_cap;        /* MSI capability offset */
        u8              msix_cap;       /* MSI-X capability offset */