[PATCH RFC 1/2] PCI: Add controller reset method

[wei.liu@kernel.org]

From: Wei Liu <wei.liu@kernel.org>

Some PCI controllers provide a function reset mechanism that is not
advertised in PCI configuration space. Allow them to expose it through an
optional pci_ops callback.

Add the controller reset method to the standard reset_method interface.
Prefer FLR and AF FLR by default, and use the controller operation before
PM and bus reset fallbacks.

Signed-off-by: Wei Liu <wei.liu@kernel.org>
---
 drivers/pci/pci.c   | 22 ++++++++++++++++++++++
 include/linux/pci.h |  3 ++-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 77b17b13ee61..4e55da202cad 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4962,6 +4962,27 @@ static int pci_reset_bus_function(struct pci_dev *dev, bool probe)
 	return rc;
 }
 
+static int pci_controller_reset(struct pci_dev *dev, bool probe)
+{
+	int rc;
+
+	if (!dev->bus->ops->reset)
+		return -ENOTTY;
+
+	if (probe)
+		return dev->bus->ops->reset(dev, probe);
+
+	rc = pci_dev_reset_iommu_prepare(dev);
+	if (rc) {
+		pci_err(dev, "failed to stop IOMMU for a PCI reset: %d\n", rc);
+		return rc;
+	}
+
+	rc = dev->bus->ops->reset(dev, probe);
+	pci_dev_reset_iommu_done(dev);
+	return rc;
+}
+
 static int cxl_reset_bus_function(struct pci_dev *dev, bool probe)
 {
 	struct pci_dev *bridge;
@@ -5094,6 +5115,7 @@ const struct pci_reset_fn_method pci_reset_fn_methods[] = {
 	{ pci_dev_acpi_reset, .name = "acpi" },
 	{ pcie_reset_flr, .name = "flr" },
 	{ pci_af_flr, .name = "af_flr" },
+	{ pci_controller_reset, .name = "controller" },
 	{ pci_pm_reset, .name = "pm" },
 	{ pci_reset_bus_function, .name = "bus" },
 	{ cxl_reset_bus_function, .name = "cxl_bus" },
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 64b308b6e61c..d7759ee70670 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -52,7 +52,7 @@
 			       PCI_STATUS_PARITY)
 
 /* Number of reset methods used in pci_reset_fn_methods array in pci.c */
-#define PCI_NUM_RESET_METHODS 8
+#define PCI_NUM_RESET_METHODS 9
 
 #define PCI_RESET_PROBE		true
 #define PCI_RESET_DO_RESET	false
@@ -875,6 +875,7 @@ struct pci_ops {
 	void __iomem *(*map_bus)(struct pci_bus *bus, unsigned int devfn, int where);
 	int (*read)(struct pci_bus *bus, unsigned int devfn, int where, int size, u32 *val);
 	int (*write)(struct pci_bus *bus, unsigned int devfn, int where, int size, u32 val);
+	int (*reset)(struct pci_dev *dev, bool probe);
 };
 
 /*
-- 
2.53.0