Commit 2fa04644 authored by Keith Busch's avatar Keith Busch Committed by Bjorn Helgaas
Browse files

PCI: Add 'reset_subordinate' to reset hierarchy below bridge 

The "bus" and "cxl_bus" reset methods reset a device by asserting Secondary
Bus Reset on the bridge leading to the device.  These only work if the
device is the only device below the bridge.

Add a sysfs 'reset_subordinate' attribute on bridges that can assert
Secondary Bus Reset regardless of how many devices are below the bridge.

This resets all the devices below a bridge in a single command, including
the locking and config space save/restore that reset methods normally do.

This may be the only way to reset devices that don't support other reset
methods (ACPI, FLR, PM reset, etc).

Link: https://lore.kernel.org/r/20241025222755.3756162-1-kbusch@meta.com


Signed-off-by: default avatarKeith Busch <kbusch@kernel.org>
[bhelgaas: commit log, add capable(CAP_SYS_ADMIN) check]
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: default avatarAlex Williamson <alex.williamson@redhat.com>
Reviewed-by: default avatarAmey Narkhede <ameynarkhede03@gmail.com>
parent 9852d85e

Documentation/ABI/testing/sysfs-bus-pci

+11 −0
Original line number Diff line number Diff line
@@ -163,6 +163,17 @@ Description: 
		will be present in sysfs.  Writing 1 to this file

		will perform reset.



What:		/sys/bus/pci/devices/.../reset_subordinate

Date:		October 2024

Contact:	linux-pci@vger.kernel.org

Description:

		This is visible only for bridge devices. If you want to reset

		all devices attached through the subordinate bus of a specific

		bridge device, writing 1 to this will try to do it.  This will

		affect all devices attached to the system through this bridge

		similiar to writing 1 to their individual "reset" file, so use

		with caution.



What:		/sys/bus/pci/devices/.../vpd

Date:		February 2008

Contact:	Ben Hutchings <bwh@kernel.org>

drivers/pci/pci-sysfs.c

+26 −0
Original line number Diff line number Diff line
@@ -521,6 +521,31 @@ 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 reset_subordinate_store(struct device *dev,

				struct device_attribute *attr,

				const char *buf, size_t count)

{

	struct pci_dev *pdev = to_pci_dev(dev);

	struct pci_bus *bus = pdev->subordinate;

	unsigned long val;



	if (!capable(CAP_SYS_ADMIN))

		return -EPERM;



	if (kstrtoul(buf, 0, &val) < 0)

		return -EINVAL;



	if (val) {

		int ret = __pci_reset_bus(bus);



		if (ret)

			return ret;

	}



	return count;

}

static DEVICE_ATTR_WO(reset_subordinate);



#if defined(CONFIG_PM) && defined(CONFIG_ACPI)

static ssize_t d3cold_allowed_store(struct device *dev,

				    struct device_attribute *attr,
@@ -625,6 +650,7 @@ static struct attribute *pci_dev_attrs[] = { 
static struct attribute *pci_bridge_attrs[] = {

	&dev_attr_subordinate_bus_number.attr,

	&dev_attr_secondary_bus_number.attr,

	&dev_attr_reset_subordinate.attr,

	NULL,

};

drivers/pci/pci.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

drivers/pci/pci.h

+1 −0
Original line number Diff line number Diff line
@@ -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;