linux-kernel - [PATCH v4 1/3] PCI: Allow PCI_DEV_FLAGS_NO_BUS

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Date:   Fri,  8 Sep 2017 10:10:31 +0200
From:   Jan Glauber <jglauber@...ium.com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     linux-pci@...r.kernel.org,
        Alex Williamson <alex.williamson@...hat.com>,
        linux-kernel@...r.kernel.org, david.daney@...ium.com,
        Jon Masters <jcm@...hat.com>,
        Robert Richter <robert.richter@...ium.com>,
        linux-arm-kernel@...ts.infradead.org, kvm@...r.kernel.org,
        Jan Glauber <jglauber@...ium.com>
Subject: [PATCH v4 1/3] PCI: Allow PCI_DEV_FLAGS_NO_BUS_RESET to be used on bus device

From: David Daney <david.daney@...ium.com>

When checking to see if a PCI bus can safely be reset, we check to see
if any of the children have their PCI_DEV_FLAGS_NO_BUS_RESET flag set.
As these devices are known not to behave well after a bus reset.

Some PCIe root port bridges also do not behave well after a bus reset,
sometimes causing the devices behind the bridge to become unusable.

Add a check for the PCI_DEV_FLAGS_NO_BUS_RESET flag being set in the
bridge device to allow these bridges to be flagged, and prevent their
buses from being reset.

A follow on patch will add a quirk for this type of bridge.

Signed-off-by: David Daney <david.daney@...ium.com>
[jglauber@...ium.com: fixed typo]
Signed-off-by: Jan Glauber <jglauber@...ium.com>
---
 drivers/pci/pci.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index fdf65a6c13f6..b2a46ca7f133 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4325,6 +4325,10 @@ static bool pci_bus_resetable(struct pci_bus *bus)
 {
 	struct pci_dev *dev;
 
+
+	if (bus->self && (bus->self->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET))
+		return false;
+
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		if (dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET ||
 		    (dev->subordinate && !pci_bus_resetable(dev->subordinate)))
-- 
2.9.0.rc0.21.g7777322