[RFC PATCH 1/2] pci: add function reset call that can be used inside of probe

[Jeff Kirsher <jeffrey.t.kirsher@intel.com>]

From: Alexander Duyck <alexander.h.duyck@intel.com>

This change makes it so that there are several new calls available.

The first is __pci_reset_dev which works similar to pci_reset_dev, however
it does not obtain the device lock.  This is important as I found several
cases such as __pci_reset_function in which the call was obtaining the
device lock even though the lock had yet to be initialized.  In addition if
one wishes to do such a reset during probe it will hang since the device
lock is already being held.

The second change that was added was a function named
pci_reset_device_function.  This function is similar to pci_reset_function
however it does not hold the device lock and so it as well can be called
during the driver probe routine.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
---

 drivers/pci/pci.c   |   74 +++++++++++++++++++++++++++++++++++++++++++--------
 include/linux/pci.h |    1 +
 2 files changed, 64 insertions(+), 11 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 60f30e7..1421bc7 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2445,17 +2445,14 @@ static int pci_parent_bus_reset(struct pci_dev *dev, int probe)
 	return 0;
 }
 
-static int pci_dev_reset(struct pci_dev *dev, int probe)
+static int __pci_dev_reset(struct pci_dev *dev, int probe)
 {
 	int rc;
 
 	might_sleep();
 
-	if (!probe) {
+	if (!probe)
 		pci_block_user_cfg_access(dev);
-		/* block PM suspend, driver probe, etc. */
-		device_lock(&dev->dev);
-	}
 
 	rc = pci_dev_specific_reset(dev, probe);
 	if (rc != -ENOTTY)
@@ -2474,11 +2471,26 @@ static int pci_dev_reset(struct pci_dev *dev, int probe)
 		goto done;
 
 	rc = pci_parent_bus_reset(dev, probe);
+
 done:
-	if (!probe) {
-		device_unlock(&dev->dev);
+	if (!probe)
 		pci_unblock_user_cfg_access(dev);
-	}
+
+	return rc;
+}
+
+static int pci_dev_reset(struct pci_dev *dev, int probe)
+{
+	int rc;
+
+	/* block PM suspend, driver probe, etc. */
+	if (!probe)
+		device_lock(&dev->dev);
+
+	rc = __pci_dev_reset(dev, probe);
+
+	if (!probe)
+		device_unlock(&dev->dev);
 
 	return rc;
 }
@@ -2502,7 +2514,7 @@ done:
  */
 int __pci_reset_function(struct pci_dev *dev)
 {
-	return pci_dev_reset(dev, 0);
+	return __pci_dev_reset(dev, 0);
 }
 EXPORT_SYMBOL_GPL(__pci_reset_function);
 
@@ -2519,7 +2531,7 @@ EXPORT_SYMBOL_GPL(__pci_reset_function);
  */
 int pci_probe_reset_function(struct pci_dev *dev)
 {
-	return pci_dev_reset(dev, 1);
+	return __pci_dev_reset(dev, 1);
 }
 
 /**
@@ -2542,7 +2554,7 @@ int pci_reset_function(struct pci_dev *dev)
 {
 	int rc;
 
-	rc = pci_dev_reset(dev, 1);
+	rc = __pci_dev_reset(dev, 1);
 	if (rc)
 		return rc;
 
@@ -2563,6 +2575,46 @@ int pci_reset_function(struct pci_dev *dev)
 EXPORT_SYMBOL_GPL(pci_reset_function);
 
 /**
+ * pci_reset_device_function - quiesce and reinitialize a PCI device function
+ * @dev: PCI device to reset
+ *
+ * Some devices allow an individual function to be reset without affecting
+ * other functions in the same device.  The PCI device must be responsive
+ * to PCI config space in order to use this function.
+ *
+ * This function is very similar to pci_reset_function, however this function
+ * does not obtain the device lock during the reset.  This is due to the fact
+ * that the call is meant to be used during probe if the reset_devices
+ * kernel parameter is set.
+ *
+ * Returns 0 if the device function was successfully reset or negative if the
+ * device doesn't support resetting a single function.
+ */
+int pci_reset_device_function(struct pci_dev *dev)
+{
+	int rc;
+
+	rc = __pci_dev_reset(dev, 1);
+	if (rc)
+		return rc;
+
+	pci_save_state(dev);
+
+	/*
+	 * both INTx and MSI are disabled after the Interrupt Disable bit
+	 * is set and the Bus Master bit is cleared.
+	 */
+	pci_write_config_word(dev, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE);
+
+	rc = __pci_dev_reset(dev, 0);
+
+	pci_restore_state(dev);
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(pci_reset_device_function);
+
+/**
  * pcix_get_max_mmrbc - get PCI-X maximum designed memory read byte count
  * @dev: PCI device to query
  *
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 6a471ab..c7708d3 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -789,6 +789,7 @@ int pcie_get_readrq(struct pci_dev *dev);
 int pcie_set_readrq(struct pci_dev *dev, int rq);
 int __pci_reset_function(struct pci_dev *dev);
 int pci_reset_function(struct pci_dev *dev);
+int pci_reset_device_function(struct pci_dev *dev);
 void pci_update_resource(struct pci_dev *dev, int resno);
 int __must_check pci_assign_resource(struct pci_dev *dev, int i);
 int pci_select_bars(struct pci_dev *dev, unsigned long flags);