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PCI: Add 'reset_subordinate' to reset hierarchy below bridge

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[ 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/[email protected]
Signed-off-by: Keith Busch <[email protected]>
[bhelgaas: commit log, add capable(CAP_SYS_ADMIN) check]
Signed-off-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Alex Williamson <[email protected]>
Reviewed-by: Amey Narkhede <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
This commit is contained in:
Keith Busch 2024-10-25 15:27:54 -07:00 • committed by Greg Kroah-Hartman
commit 88da5d46b6
4 changed files with 39 additions and 1 deletions
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11
Documentation/ABI/testing/sysfs-bus-pci
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@ -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: [email protected]
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 <[email protected]>