linux-kernel - [PATCH 1/2] PCI: Implement pci_reset_function

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Date:   Mon, 10 Jul 2017 16:52:29 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [PATCH 1/2] PCI: Implement pci_reset_function_locked

The implementation of PCI workarounds may require that the device
is reset from its probe function. This implies that the PCI device
lock is already held, and makes calling pci_reset_function impossible
(since it will itself try to take that lock).

This patch introduces pci_reset_function_locked, which is the equivalent
of pci_reset_function, except that it requires the PCI device lock to
be already held by the caller.

Signed-off-by: Marc Zyngier <marc.zyngier@....com>
---
 drivers/pci/pci.c   | 35 +++++++++++++++++++++++++++++++++++
 include/linux/pci.h |  1 +
 2 files changed, 36 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 563901cd9c06..a2c3e8b94f65 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4287,6 +4287,41 @@ int pci_reset_function(struct pci_dev *dev)
 EXPORT_SYMBOL_GPL(pci_reset_function);
 
 /**
+ * pci_reset_function_locked - quiesce and reset 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 does not just reset the PCI portion of a device, but
+ * clears all the state associated with the device.  This function differs
+ * from __pci_reset_function in that it saves and restores device state
+ * over the reset. it also differs from pci_reset_function in that it
+ * requires the PCI device lock to be held.
+ *
+ * Returns 0 if the device function was successfully reset or negative if the
+ * device doesn't support resetting a single function.
+ */
+int pci_reset_function_locked(struct pci_dev *dev)
+{
+	int rc;
+
+	rc = pci_dev_reset(dev, 1);
+	if (rc)
+		return rc;
+
+	pci_dev_save_and_disable(dev);
+
+	rc = __pci_dev_reset(dev, 0);
+
+	pci_dev_restore(dev);
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(pci_reset_function_locked);
+
+/**
  * pci_try_reset_function - quiesce and reset a PCI device function
  * @dev: PCI device to reset
  *
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 8039f9f0ca05..16be18678ca1 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1049,6 +1049,7 @@ void pcie_flr(struct pci_dev *dev);
 int __pci_reset_function(struct pci_dev *dev);
 int __pci_reset_function_locked(struct pci_dev *dev);
 int pci_reset_function(struct pci_dev *dev);
+int pci_reset_function_locked(struct pci_dev *dev);
 int pci_try_reset_function(struct pci_dev *dev);
 int pci_probe_reset_slot(struct pci_slot *slot);
 int pci_reset_slot(struct pci_slot *slot);
-- 
2.11.0