linux-kernel - [PATCH 1/1] Enable LTR/OBFF before device is used by driver

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Date:	Mon, 14 May 2012 10:48:16 +0800
From:	Xudong Hao <xudong.hao@...ux.intel.com>
To:	bhelgaas@...gle.com
Cc:	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, avi@...hat.com, alex.williamson@...hat.com,
	xiantao.zhang@...el.com, xudong.hao@...el.com
Subject: [PATCH 1/1] Enable LTR/OBFF before device is used by driver

Enable LTR(Latency tolerance reporting) and OBFF(optimized buffer flush/fill) in
 pci_enable_device(), so that they are enabled before the device is used by driver.

Signed-off-by: Xudong Hao <xudong.hao@...el.com>

---
 drivers/pci/pci.c |   29 +++++++++++++++++++++++++++++
 1 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 111569c..2369883 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1134,6 +1134,31 @@ int pci_load_and_free_saved_state(struct pci_dev *dev,
 }
 EXPORT_SYMBOL_GPL(pci_load_and_free_saved_state);

+static void pci_enable_dev_caps(struct pci_dev *dev)
+{
+       /* set default value */
+       unsigned long type = PCI_EXP_OBFF_SIGNAL_ALWAYS;
+
+       /* LTR(Latency tolerance reporting) allows devices to send
+        * messages to the root complex indicating their latency
+        * tolerance for snooped & unsnooped memory transactions.
+        */
+       pci_enable_ltr(dev);
+
+       /* OBFF (optimized buffer flush/fill), where supported,
+        * can help improve energy efficiency by giving devices
+        * information about when interrupts and other activity
+        * will have a reduced power impact.
+        */
+       pci_enable_obff(dev, type);
+}
+
+static void pci_disable_dev_caps(struct pci_dev *dev)
+{
+       pci_disable_obff(dev);
+       pci_disable_ltr(dev);
+}
+
 static int do_pci_enable_device(struct pci_dev *dev, int bars)
 {
        int err;
@@ -1146,6 +1171,9 @@ static int do_pci_enable_device(struct pci_dev *dev, int bars)
                return err;
        pci_fixup_device(pci_fixup_enable, dev);

+       /* Enable some device capibility before it's used by driver. */
+       pci_enable_dev_caps(dev);
+
        return 0;
 }

@@ -1361,6 +1389,7 @@ static void do_pci_disable_device(struct pci_dev *dev)
        }

        pcibios_disable_device(dev);
+       pci_disable_dev_caps(dev);
 }

 /**
--
1.6.0.rc1

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