linux-kernel - [PATCH 1/2] PCI: save and restore device state during bus reset

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Date:   Thu,  1 Sep 2016 19:00:00 -0400
From:   Sinan Kaya <okaya@...eaurora.org>
To:     linux-pci@...r.kernel.org, timur@...eaurora.org,
        cov@...eaurora.org, alex.williamson@...hat.com,
        vikrams@...eaurora.org
Cc:     linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Sinan Kaya <okaya@...eaurora.org>, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] PCI: save and restore device state during bus reset

A secondary bus reset causes settings to be lost by all downstream
devices on the tree. The code is currently saving and restoring device
states only when called from the VFIO path via pci_probe_reset_bus
and pci_reset_bus functions.

Moving the save and restore into pci_reset_bridge_secondary_bus
so that all users of the API have the same behavior.

Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
---
 drivers/pci/pci.c | 36 +++++++++++++++---------------------
 1 file changed, 15 insertions(+), 21 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index aab9d51..b209378 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3860,19 +3860,6 @@ void __weak pcibios_reset_secondary_bus(struct pci_dev *dev)
 	pci_reset_secondary_bus(dev);
 }
 
-/**
- * pci_reset_bridge_secondary_bus - Reset the secondary bus on a PCI bridge.
- * @dev: Bridge device
- *
- * Use the bridge control register to assert reset on the secondary bus.
- * Devices on the secondary bus are left in power-on state.
- */
-void pci_reset_bridge_secondary_bus(struct pci_dev *dev)
-{
-	pcibios_reset_secondary_bus(dev);
-}
-EXPORT_SYMBOL_GPL(pci_reset_bridge_secondary_bus);
-
 static int pci_parent_bus_reset(struct pci_dev *dev, int probe)
 {
 	struct pci_dev *pdev;
@@ -4362,6 +4349,21 @@ static void pci_slot_restore(struct pci_slot *slot)
 	}
 }
 
+/**
+ * pci_reset_bridge_secondary_bus - Reset the secondary bus on a PCI bridge.
+ * @dev: Bridge device
+ *
+ * Use the bridge control register to assert reset on the secondary bus.
+ * Devices on the secondary bus are left in power-on state.
+ */
+void pci_reset_bridge_secondary_bus(struct pci_dev *dev)
+{
+	pci_bus_save_and_disable(dev->bus);
+	pcibios_reset_secondary_bus(dev);
+	pci_bus_restore(dev->bus);
+}
+EXPORT_SYMBOL_GPL(pci_reset_bridge_secondary_bus);
+
 static int pci_slot_reset(struct pci_slot *slot, int probe)
 {
 	int rc;
@@ -4504,12 +4506,8 @@ int pci_reset_bus(struct pci_bus *bus)
 	if (rc)
 		return rc;
 
-	pci_bus_save_and_disable(bus);
-
 	rc = pci_bus_reset(bus, 0);
 
-	pci_bus_restore(bus);
-
 	return rc;
 }
 EXPORT_SYMBOL_GPL(pci_reset_bus);
@@ -4528,8 +4526,6 @@ int pci_try_reset_bus(struct pci_bus *bus)
 	if (rc)
 		return rc;
 
-	pci_bus_save_and_disable(bus);
-
 	if (pci_bus_trylock(bus)) {
 		might_sleep();
 		pci_reset_bridge_secondary_bus(bus->self);
@@ -4537,8 +4533,6 @@ int pci_try_reset_bus(struct pci_bus *bus)
 	} else
 		rc = -EAGAIN;
 
-	pci_bus_restore(bus);
-
 	return rc;
 }
 EXPORT_SYMBOL_GPL(pci_try_reset_bus);
-- 
1.9.1