linux-kernel - [PATCH v3 6/7] PCI/ATS: Disable PF/VF ATS service independently

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Date:   Thu, 20 Jun 2019 13:38:47 -0700
From:   sathyanarayanan.kuppuswamy@...ux.intel.com
To:     bhelgaas@...gle.com
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        ashok.raj@...el.com, keith.busch@...el.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: [PATCH v3 6/7] PCI/ATS: Disable PF/VF ATS service independently

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

Currently all VF's needs to be disable their ATS service before
disabling the ATS service in corresponding PF device. But this logic is
incorrect and does not align with the spec. Also it might lead to
some power and performance impact in the system. As per PCIe spec r4.0,
sec 9.3.7.8, ATS Capabilities in VFs and their associated PFs may be
enabled/disabled independently. So remove this dependency logic in
enable/disable code.

Cc: Ashok Raj <ashok.raj@...el.com>
Cc: Keith Busch <keith.busch@...el.com>
Suggested-by: Ashok Raj <ashok.raj@...el.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
---
 drivers/pci/ats.c   | 11 -----------
 include/linux/pci.h |  1 -
 2 files changed, 12 deletions(-)

diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index 13fe88829306..8ee2c1123b84 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -140,8 +140,6 @@ 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);
@@ -159,20 +157,11 @@ 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 a317c3115d69..442ced0d2dd1 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -449,7 +449,6 @@ 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
 	struct mutex	pri_lock;	/* PRI enable lock */
-- 
2.21.0