[RFC PATCH 3/3] PCI: support Secondary Bus Reset

[Yu Zhao <yu.zhao@intel.com>]

PCI-to-PCI Bridge 1.2 specifies that the Secondary Bus Reset bit can
force the assertion of RST# on the secondary interface, which can be
used to reset all devices including subordinates under this bus. This
can be used to reset a function if this function is the only device
under this bus.

Signed-off-by: Yu Zhao <yu.zhao@intel.com>
---
 drivers/pci/pci.c |   31 +++++++++++++++++++++++++++++++
 1 files changed, 31 insertions(+), 0 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e459a0b..a77c33a 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2115,6 +2115,33 @@ static int pci_pm_flr(struct pci_dev *dev, int probe)
 	return 0;
 }
 
+static int pci_secondary_bus_reset(struct pci_dev *dev, int probe)
+{
+	u16 ctrl;
+	struct pci_dev *pdev;
+
+	if (dev->subordinate)
+		return -ENOTTY;
+
+	list_for_each_entry(pdev, &dev->bus->devices, bus_list)
+		if (pdev != dev)
+			return -ENOTTY;
+
+	if (probe)
+		return 0;
+
+	pci_read_config_word(dev->bus->self, PCI_BRIDGE_CONTROL, &ctrl);
+	ctrl |= PCI_BRIDGE_CTL_BUS_RESET;
+	pci_write_config_word(dev->bus->self, PCI_BRIDGE_CONTROL, ctrl);
+	msleep(100);
+
+	ctrl &= ~PCI_BRIDGE_CTL_BUS_RESET;
+	pci_write_config_word(dev->bus->self, PCI_BRIDGE_CONTROL, ctrl);
+	msleep(100);
+
+	return 0;
+}
+
 static int pci_dev_reset(struct pci_dev *dev, int probe)
 {
 	int rc;
@@ -2136,6 +2163,10 @@ static int pci_dev_reset(struct pci_dev *dev, int probe)
 		goto done;
 
 	rc = pci_pm_flr(dev, probe);
+	if (rc != -ENOTTY)
+		goto done;
+
+	rc = pci_secondary_bus_reset(dev, probe);
 done:
 	up(&dev->dev.sem);
 
-- 
1.5.6.4