[PATCH 6/6] pci: implement function level reset

[Sascha Hauer <s.hauer@pengutronix.de>]

This will be needed for upcoming LS1028a support. The code is taken from
U-Boot which suffices for our usecase. The kernel code is much more
elaborated here.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 drivers/pci/pci.c   | 32 ++++++++++++++++++++++++++++++++
 include/linux/pci.h |  2 ++
 2 files changed, 34 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index a3e7e70871..84678e40a9 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -553,6 +553,38 @@ pci_of_match_device(struct device *parent, unsigned int devfn)
 	return NULL;
 }
 
+/**
+ * pcie_flr - initiate a PCIe function level reset
+ * @dev:	device to reset
+ *
+ * Initiate a function level reset on @dev.
+ */
+int pci_flr(struct pci_dev *pdev)
+{
+	u16 val;
+	int pcie_off;
+	u32 cap;
+
+	/* look for PCI Express Capability */
+	pcie_off = pci_find_capability(pdev, PCI_CAP_ID_EXP);
+	if (!pcie_off)
+		return -ENOENT;
+
+	/* check FLR capability */
+	pci_read_config_dword(pdev, pcie_off + PCI_EXP_DEVCAP, &cap);
+	if (!(cap & PCI_EXP_DEVCAP_FLR))
+		return -ENOENT;
+
+	pci_read_config_word(pdev, pcie_off + PCI_EXP_DEVCTL, &val);
+	val |= PCI_EXP_DEVCTL_BCR_FLR;
+	pci_write_config_word(pdev, pcie_off + PCI_EXP_DEVCTL, val);
+
+	/* wait 100ms, per PCI spec */
+	mdelay(100);
+
+	return 0;
+}
+
 static unsigned int pci_scan_bus(struct pci_bus *bus)
 {
 	struct pci_dev *dev;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 0e907209a7..fe5285116a 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -329,6 +329,8 @@ u8 pci_find_capability(struct pci_dev *dev, int cap);
 
 extern void __iomem *pci_iomap(struct pci_dev *dev, int bar);
 
+int pci_flr(struct pci_dev *pdev);
+
 /*
  * The world is not perfect and supplies us with broken PCI devices.
  * For at least a part of these bugs we need a work-around, so both
-- 
2.39.2