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PCI: Add 'reset_subordinate' to reset hierarchy below bridge

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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: Keith Busch <kbusch@kernel.org>
[bhelgaas: commit log, add capable(CAP_SYS_ADMIN) check]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Amey Narkhede <ameynarkhede03@gmail.com>
This commit is contained in:
Keith Busch 2024-10-25 15:27:54 -07:00 committed by Bjorn Helgaas
parent 9852d85ec9
commit 2fa046449a
4 changed files with 39 additions and 1 deletions
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11
Documentation/ABI/testing/sysfs-bus-pci
View File

@ -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>

26
drivers/pci/pci-sysfs.c
View File

@ -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,
};

2
drivers/pci/pci.c
View File

@ -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;

1
drivers/pci/pci.h
View File

@ -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;