[PATCH v2 3/3] PCI/AER: Provide reset_link for firmware first root port

[Betty Dall <betty.dall@hp.com>]

The firmware first path does not install the aerdrv root port
service driver, so the firmware first root port does not have
a reset_link callback. When a firmware first root port does not have
a reset_link callback, use a new default reset_link similar to what
we already do for the default_downstream_reset_link(). The firmware
first default reset_link brings the root port out of SBR if firmware
left it in SBR.

Changes since v1:
Removed incorrect setting of p2p_ctrl after the read.

Signed-off-by: Betty Dall <betty.dall@hp.com>
---

 drivers/pci/pcie/aer/aerdrv_core.c |   36 ++++++++++++++++++++++++++++++++++++
 1 files changed, 36 insertions(+), 0 deletions(-)


diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c
index 8ec8b4f..72f76cd 100644
--- a/drivers/pci/pcie/aer/aerdrv_core.c
+++ b/drivers/pci/pcie/aer/aerdrv_core.c
@@ -413,6 +413,39 @@ static pci_ers_result_t default_downstream_reset_link(struct pci_dev *dev)
 	return PCI_ERS_RESULT_RECOVERED;
 }
 
+/**
+ * default_ff_root_port_reset_link - default reset function for firmware
+ *		first Root Port
+ * @dev: pointer to root port's pci_dev data structure
+ *
+ * Invoked when performing link reset at Root Port w/ no aer driver.
+ * This happens through the firmware first path. Firmware may leave
+ * the Root Port in SBR and it is the OS responsiblity to bring it out
+ * of SBR.
+ */
+static pci_ers_result_t default_ff_root_port_reset_link(struct pci_dev *dev)
+{
+	u16 p2p_ctrl;
+
+	/* Read Secondary Bus Reset */
+	pci_read_config_word(dev, PCI_BRIDGE_CONTROL, &p2p_ctrl);
+
+	/* De-assert Secondary Bus Reset, if it is set */
+	if (p2p_ctrl & PCI_BRIDGE_CTL_BUS_RESET) {
+		p2p_ctrl &= ~PCI_BRIDGE_CTL_BUS_RESET;
+		pci_write_config_word(dev, PCI_BRIDGE_CONTROL, p2p_ctrl);
+
+		/*
+		 * System software must wait for at least 100ms from the end
+		 * of a reset of one or more device before it is permitted
+		 * to issue Configuration Requests to those devices.
+		 */
+		msleep(200);
+		dev_dbg(&dev->dev, "Root Port link has been reset\n");
+	}
+	return PCI_ERS_RESULT_RECOVERED;
+}
+
 static int find_aer_service_iter(struct device *device, void *data)
 {
 	struct pcie_port_service_driver *service_driver, **drv;
@@ -460,6 +493,9 @@ static pci_ers_result_t reset_link(struct pci_dev *dev)
 		status = driver->reset_link(udev);
 	} else if (pci_pcie_type(udev) == PCI_EXP_TYPE_DOWNSTREAM) {
 		status = default_downstream_reset_link(udev);
+	} else if (pci_pcie_type(udev) == PCI_EXP_TYPE_ROOT_PORT &&
+		pcie_aer_get_firmware_first(udev)) {
+		status = default_ff_root_port_reset_link(udev);
 	} else {
 		dev_printk(KERN_DEBUG, &dev->dev,
 			"no link-reset support at upstream device %s\n",