From: Keith Busch kbusch@kernel.org
[ Upstream commit 2fa046449a82a7d0f6d9721dd83e348816038444 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- Documentation/ABI/testing/sysfs-bus-pci | 11 +++++++++++ drivers/pci/pci-sysfs.c | 26 +++++++++++++++++++++++++ drivers/pci/pci.c | 2 +- drivers/pci/pci.h | 1 + 4 files changed, 39 insertions(+), 1 deletion(-)
diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci index ecf47559f495b..7f3e6bc3ff0ff 100644 --- a/Documentation/ABI/testing/sysfs-bus-pci +++ b/Documentation/ABI/testing/sysfs-bus-pci @@ -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 diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index 3317b93547167..92e8ac85f58e8 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -517,6 +517,31 @@ 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, @@ -621,6 +646,7 @@ 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, };
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 93f2f4dcf6d69..fb702d17ed9a7 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -6068,7 +6068,7 @@ 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 d5e9010a135a1..83cd646bde3f0 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -46,6 +46,7 @@ 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;