linux-kernel - [PATCH v2 4/5] PCI/ATS: Disable PF/VF ATS service independently

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Date:   Mon,  6 May 2019 10:20:06 -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 v2 4/5] 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 718e6f414680..977f5a1ace40 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -72,8 +72,6 @@ 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);
@@ -91,20 +89,11 @@ 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 2a761ea63f8d..c38cbf8fa03b 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -446,7 +446,6 @@ 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 */
-- 
2.20.1