[PATCH] pci: provide bus reset attribute

[Keith Busch <kbusch@meta.com>]

From: Keith Busch <kbusch@kernel.org>

Attempting a bus reset on an end device only works if it's the only
function on or below that bus.

Provide an attribute on the pci_bus device that can perform the
secondary bus reset. This makes it possible for a user to safely reset
multiple devices in a single command using the secondary bus reset
method.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 drivers/pci/pci-sysfs.c | 23 +++++++++++++++++++++++
 drivers/pci/pci.c       |  2 +-
 drivers/pci/pci.h       |  1 +
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 5d0f4db1cab78..616d64f12da4d 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -521,6 +521,28 @@ static ssize_t bus_rescan_store(struct device *dev,
 static struct device_attribute dev_attr_bus_rescan = __ATTR(rescan, 0200, NULL,
 							    bus_rescan_store);
 
+static ssize_t bus_reset_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	struct pci_bus *bus = to_pci_bus(dev);
+	unsigned long val;
+
+	if (kstrtoul(buf, 0, &val) < 0)
+		return -EINVAL;
+
+	if (val) {
+		int ret = __pci_reset_bus(bus);
+
+		if (ret)
+			return ret;
+	}
+
+	return count;
+}
+static struct device_attribute dev_attr_bus_reset = __ATTR(reset, 0200, NULL,
+							   bus_reset_store);
+
 #if defined(CONFIG_PM) && defined(CONFIG_ACPI)
 static ssize_t d3cold_allowed_store(struct device *dev,
 				    struct device_attribute *attr,
@@ -638,6 +660,7 @@ static struct attribute *pcie_dev_attrs[] = {
 
 static struct attribute *pcibus_attrs[] = {
 	&dev_attr_bus_rescan.attr,
+	&dev_attr_bus_reset.attr,
 	&dev_attr_cpuaffinity.attr,
 	&dev_attr_cpulistaffinity.attr,
 	NULL,
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 7d85c04fbba2a..338dfcd983f1e 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5880,7 +5880,7 @@ EXPORT_SYMBOL_GPL(pci_probe_reset_bus);
  *
  * Same as above except return -EAGAIN if the bus cannot be locked
  */
-static int __pci_reset_bus(struct pci_bus *bus)
+int __pci_reset_bus(struct pci_bus *bus)
 {
 	int rc;
 
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 14d00ce45bfa9..1cdc2c9547a7e 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -104,6 +104,7 @@ bool pci_reset_supported(struct pci_dev *dev);
 void pci_init_reset_methods(struct pci_dev *dev);
 int pci_bridge_secondary_bus_reset(struct pci_dev *dev);
 int pci_bus_error_reset(struct pci_dev *dev);
+int __pci_reset_bus(struct pci_bus *bus);
 
 struct pci_cap_saved_data {
 	u16		cap_nr;
-- 
2.43.5