linux-kernel - [PATCH 3/5] PCI/ATS: Disable PF/VF ATS service independently

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Message-Id: <20190905193146.90250-4-helgaas@kernel.org>
Date:   Thu,  5 Sep 2019 14:31:44 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Ashok Raj <ashok.raj@...el.com>,
        Keith Busch <keith.busch@...el.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: [PATCH 3/5] PCI/ATS: Disable PF/VF ATS service independently

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

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@...el.com>
Link: https://lore.kernel.org/r/8163ab8fa66afd2cba514ae95d29ab12104781aa.1567029860.git.sathyanarayanan.kuppuswamy@linux.intel.com
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Ashok Raj <ashok.raj@...el.com>
Cc: Keith Busch <keith.busch@...el.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 ab928f8267cf..920deeccf38d 100644
--- 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 9e700d9f9f28..a73e8d28a896 100644
--- 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 */
-- 
2.23.0.187.g17f5b7556c-goog