From: Keith Busch <kbusch@xxxxxxxxxx> [ 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@xxxxxxxx Signed-off-by: Keith Busch <kbusch@xxxxxxxxxx> [bhelgaas: commit log, add capable(CAP_SYS_ADMIN) check] Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> Reviewed-by: Alex Williamson <alex.williamson@xxxxxxxxxx> Reviewed-by: Amey Narkhede <ameynarkhede03@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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 44d4b2be92fd4..c68d1d9a4d479 100644 --- a/Documentation/ABI/testing/sysfs-bus-pci +++ b/Documentation/ABI/testing/sysfs-bus-pci @@ -125,6 +125,17 @@ 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@xxxxxxxxxxxxxxx +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@xxxxxxxxxx> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index f68798763af8d..d5287dfac9171 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -507,6 +507,31 @@ static ssize_t dev_bus_rescan_store(struct device *dev, } static DEVICE_ATTR(rescan, (S_IWUSR|S_IWGRP), NULL, dev_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, @@ -778,6 +803,7 @@ 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 aa2be8d815048..e22040c8a0aec 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -5295,7 +5295,7 @@ 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 39725b71300f8..1db9b8ff6043d 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -36,6 +36,7 @@ int pci_mmap_fits(struct pci_dev *pdev, int resno, struct vm_area_struct *vmai, int pci_probe_reset_function(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_platform_pm_ops - Firmware PM callbacks -- 2.43.0
