PCI/ATS: Disable PF/VF ATS service independently

Previously we didn't disable the PF ATS until all associated VFs had
disabled it.  But per PCIe spec r5.0, sec 9.3.7.8, the ATS Capability in
VFs and associated PFs may be enabled independently.  Leaving ATS enabled
in the PF unnecessarily may have power and performance impacts.

Remove this dependency logic in the ATS enable/disable code.

[bhelgaas: commit log]
Suggested-by: Ashok Raj <ashok.raj@intel.com>
Link: https://lore.kernel.org/r/8163ab8fa66afd2cba514ae95d29ab12104781aa.1567029860.git.sathyanarayanan.kuppuswamy@linux.intel.com
Link: https://lore.kernel.org/r/20190905193146.90250-4-helgaas@kernel.org
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Keith Busch <keith.busch@intel.com>

diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index fb5cfd2..a708ed4 100644 (file)
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -60,8 +60,6 @@ int pci_enable_ats(struct pci_dev *dev, int ps)
                pdev = pci_physfn(dev);
                if (pdev->ats_stu != ps)
                        return -EINVAL;
-
-               atomic_inc(&pdev->ats_ref_cnt);  /* count enabled VFs */
        } else {
                dev->ats_stu = ps;
                ctrl |= PCI_ATS_CTRL_STU(dev->ats_stu - PCI_ATS_MIN_STU);
@@ -79,20 +77,11 @@ EXPORT_SYMBOL_GPL(pci_enable_ats);
  */
 void pci_disable_ats(struct pci_dev *dev)
 {
-       struct pci_dev *pdev;
        u16 ctrl;
 
        if (WARN_ON(!dev->ats_enabled))
                return;
 
-       if (atomic_read(&dev->ats_ref_cnt))
-               return;         /* VFs still enabled */
-
-       if (dev->is_virtfn) {
-               pdev = pci_physfn(dev);
-               atomic_dec(&pdev->ats_ref_cnt);
-       }
-
        pci_read_config_word(dev, dev->ats_cap + PCI_ATS_CTRL, &ctrl);
        ctrl &= ~PCI_ATS_CTRL_ENABLE;
        pci_write_config_word(dev, dev->ats_cap + PCI_ATS_CTRL, ctrl);

diff --git a/include/linux/pci.h b/include/linux/pci.h
index f9088c8..c028883 100644 (file)
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -452,7 +452,6 @@ struct pci_dev {
        };
        u16             ats_cap;        /* ATS Capability offset */
        u8              ats_stu;        /* ATS Smallest Translation Unit */
-       atomic_t        ats_ref_cnt;    /* Number of VFs with ATS enabled */
 #endif
 #ifdef CONFIG_PCI_PRI
        u32             pri_reqs_alloc; /* Number of PRI requests allocated */